1. Introduction
1.1 Safety Information
1.2 Environmental conditions
2. Presentation
2.1 Common elements
2.2 Specific elements
2.3 Functional insulation
2.4 Optional accessories
3. First steps
3.1 Prerequisites
3.2 Testing USB connectivity
3.3 Localization
3.4 Test of the module
3.5 Configuration
4. Assembly and connections
4.1 Fixing
4.2 Assembly examples
4.3 USB power distribution
4.4 Electromagnetic compatibility (EMI)
5. Programming, general concepts
5.1 Programming paradigm
5.2 The Yocto-MaxiCoupler module
5.3 Module control interface
5.4 Relay function interface
5.5 What interface: Native, DLL or Service ?
5.6 Programming, where to start?
6. Using the Yocto-MaxiCoupler in command line
6.1 Installing
6.2 Use: general description
6.3 Control of the Relay function
6.4 Control of the module part
6.5 Limitations
7. Using Yocto-MaxiCoupler with JavaScript / EcmaScript
7.1 Blocking I/O versus Asynchronous I/O in JavaScript
7.2 Using Yoctopuce library for JavaScript / EcmaScript 2017
7.3 Control of the Relay function
7.4 Control of the module part
7.5 Error handling
8. Using Yocto-MaxiCoupler with PHP
8.1 Getting ready
8.2 Control of the Relay function
8.3 Control of the module part
8.4 HTTP callback API and NAT filters
8.5 Error handling
9. Using Yocto-MaxiCoupler with C++
9.1 Control of the Relay function
9.2 Control of the module part
9.3 Error handling
9.4 Integration variants for the C++ Yoctopuce library
10. Using Yocto-MaxiCoupler with Objective-C
10.1 Control of the Relay function
10.2 Control of the module part
10.3 Error handling
11. Using Yocto-MaxiCoupler with Visual Basic .NET
11.1 Installation
11.2 Using the Yoctopuce API in a Visual Basic project
11.3 Control of the Relay function
11.4 Control of the module part
11.5 Error handling
12. Using Yocto-MaxiCoupler with C#
12.1 Installation
12.2 Using the Yoctopuce API in a Visual C# project
12.3 Control of the Relay function
12.4 Control of the module part
12.5 Error handling
13. Using the Yocto-MaxiCoupler with Universal Windows Platform
13.1 Blocking and asynchronous functions
13.2 Installation
13.3 Using the Yoctopuce API in a Visual Studio project
13.4 Control of the Relay function
13.5 A real example
13.6 Control of the module part
13.7 Error handling
14. Using Yocto-MaxiCoupler with Delphi
14.1 Preparation
14.2 Control of the Relay function
14.3 Control of the module part
14.4 Error handling
15. Using the Yocto-MaxiCoupler with Python
15.1 Source files
15.2 Dynamic library
15.3 Control of the Relay function
15.4 Control of the module part
15.5 Error handling
16. Using the Yocto-MaxiCoupler with Java
16.1 Getting ready
16.2 Control of the Relay function
16.3 Control of the module part
16.4 Error handling
17. Using the Yocto-MaxiCoupler with Android
17.1 Native access and VirtualHub
17.2 Getting ready
17.3 Compatibility
17.4 Activating the USB port under Android
17.5 Control of the Relay function
17.6 Control of the module part
17.7 Error handling
18. Advanced programming
18.1 Event programming
19. Firmware Update
19.1 The VirtualHub or the YoctoHub
19.2 The command line library
19.3 The Android application Yocto-Firmware
19.4 Updating the firmware with the programming library
19.5 The "update" mode
20. Using with unsupported languages
20.1 Command line
20.2 VirtualHub and HTTP GET
20.3 Using dynamic libraries
20.4 Porting the high level library
21. High-level API Reference
21.1 General functions
21.2 Module control interface
21.3 Relay function interface
22. Troubleshooting
22.1 Where to start?
22.2 Programming examples don't seem to work
22.3 Linux and USB
22.4 ARM Platforms: HF and EL
22.5 Powered module but invisible for the OS
22.6 Another process named xxx is already using yAPI
22.7 Disconnections, erratic behavior
22.8 Damaged device
23. Characteristics
24. Index

1. Introduction

The Yocto-MaxiCoupler is a 50x58.3mm electronic module which allows you to control small solid state relays by USB. These relays can commute up to 60V DC and 0.1A. This allows you to pilot small equipments by acting directly on their power supply or drive much bigger electromechanical relays The module small dimensions enable it to be slipped almost anywhere, including inside the piloted equipment.

The Yocto-MaxiCoupler module

The Yocto-MaxiCoupler is not in itself a complete product. It is a component intended to be integrated into a solution used in laboratory equipments, or in industrial process-control equipments, or for similar applications in domestic and commercial environments. In order to use it, you must at least install it in a protective enclosure and connect it to a host computer.

Yoctopuce thanks you for buying this Yocto-MaxiCoupler and sincerely hopes that you will be satisfied with it. The Yoctopuce engineers have put a large amount of effort to ensure that your Yocto-MaxiCoupler is easy to install anywhere and easy to drive from a maximum of programming languages. If you are nevertheless disappointed with this module, or if you need additional information, do not hesitate to contact Yoctopuce support:

E-mail address:	support@yoctopuce.com
Web site:	www.yoctopuce.com
Postal address:	Chemin des Journaliers, 1
ZIP code, city:	1236 Cartigny
Country:	Switzerland

1.1. Safety Information

The Yocto-MaxiCoupler is designed to meet the requirements of IEC 61010-1:2010 safety standard. It does not create any serious hazards to the operator and surrounding area, even in single fault condition, as long as it is integrated and used according to the instructions contained in this documentation, and in this section in particular.

Protective enclosure

The Yocto-MaxiCoupler should not be used without a protective enclosure, because of the accessible bare electronic components. For optimal safety, it should be put into a non-metallic, non-inflammable enclosure, resistant to a mechanical stress level of 5 J. For instance, use a polycarbonate (e.g. LEXAN) enclosure rated IK08 with a IEC 60695-11-10 flammability rating of V-1 or better. Using a lower quality enclosure may require specific warnings for the operator and/or compromise conformity with the safety standard.

Maintenance

If a damage is observed on the electronic board or on the enclosure, it should be replaced in order to ensure continued safety of the equipment, and to prevent damaging other parts of the system due to overload that a short circuit could cause.

Identification

In order to ease the maintenance and the identification of risks during maintenance, you should affixate the water-resistant identification label provided together with the electronic board as close as possible to the device. If the device is put in a dedicated enclosure, the identification label should be affixated on the outside of the enclosure.

Application

The safety standard applied is intended to cover laboratory equipment, industrial process-control equipment and similar applications in residential or commercial environment. If you intend to use the Yocto-MaxiCoupler for another kind of application, you should check the safety regulations according to the standard applicable to your application.

In particular, the Yocto-MaxiCoupler is not certified for use in medical environments or for life-support applications.

Environment

The Yocto-MaxiCoupler is not certified for use in hazardous locations, explosive environments, or life-threatening applications. Environmental ratings are provided below.

IEC 61140 Protection Class III

The Yocto-MaxiCoupler has been designed to work with safety extra-low voltages only. Do not exceed voltages indicated in this manual, and never connect to the Yocto-MaxiCoupler terminal blocks any wire that could be connected to the mains.

1.2. Environmental conditions

Yoctopuce devices have been designed for indoor use in a standard office or laboratory environment (IEC 60664 pollution degree 2): air pollution is expected to be limited and mainly non-conductive. Relative humidity is expected to be between 10% and 90% RH, non condensing. Use in environments with significant solid pollution or conductive pollution requires a protection from such pollution using an IP67 or IP68 enclosure. The products are designed for use up to altitude 2000m.

All Yoctopuce devices are warranted to perform according to their documentation and technical specifications under normal temperature conditions according to IEC61010-1, i.e. 5°C to 40°C. In addition, most devices can also be used on an extended temperature range, where some limitations may apply from case to case.

The extended operating temperature range for the Yocto-MaxiCoupler is -30...85°C. This temperature range has been determined based on components manufacturer recommendations, and on controlled environment tests performed during a limited duration (1h). If you plan to use the Yocto-MaxiCoupler in harsh environments for a long period of time, we strongly advise you to run extensive tests before going to production.

2. Presentation

1:	USB socket	4:	State led for relay 1
2:	Yocto-button	5:	State led for relay 2
3:	Yocto-led	6:	Relay 1 terminal
		7:	Relay 2 terminal

2.1. Common elements

All Yocto-modules share a number of common functionalities.

USB connector

Yoctopuce modules all come with a USB 2.0 micro-B socket. Warning: the USB connector is simply soldered in surface and can be pulled out if the USB plug acts as a lever. In this case, if the tracks stayed in position, the connector can be soldered back with a good iron and using flux to avoid bridges. Alternatively, you can solder a USB cable directly in the 1.27mm-spaced holes near the connector.

If you plan to use a power source other then a standard USB host port to power the device through the USB connector, that power source must respect the assigned values of USB 2.0 specifications:

• Voltage min.: 4.75 V DC
• Voltage max.: 5.25 V DC
• Over-current protection: 5.0 A max.

Yocto-button

The Yocto-button has two functionalities. First, it can activate the Yocto-beacon mode (see below under Yocto-led). Second, if you plug in a Yocto-module while keeping this button pressed, you can then reprogram its firmware with a new version. Note that there is a simpler UI-based method to update the firmware, but this one works even in case of severely damaged firmware.

Yocto-led

Normally, the Yocto-led is used to indicate that the module is working smoothly. The Yocto-led then emits a low blue light which varies slowly, mimicking breathing. The Yocto-led stops breathing when the module is not communicating any more, as for instance when powered by a USB hub which is disconnected from any active computer.

When you press the Yocto-button, the Yocto-led switches to Yocto-beacon mode. It starts flashing faster with a stronger light, in order to facilitate the localization of a module when you have several identical ones. It is indeed possible to trigger off the Yocto-beacon by software, as it is possible to detect by software that a Yocto-beacon is on.

The Yocto-led has a third functionality, which is less pleasant: when the internal software which controls the module encounters a fatal error, the Yocto-led starts emitting an SOS in morse ¹. If this happens, unplug and re-plug the module. If it happens again, check that the module contains the latest version of the firmware, and, if it is the case, contact Yoctopuce support².

Current sensor

Each Yocto-module is able to measure its own current consumption on the USB bus. Current supply on a USB bus being quite critical, this functionality can be of great help. You can only view the current consumption of a module by software.

Serial number

Each Yocto-module has a unique serial number assigned to it at the factory. For Yocto-MaxiCoupler modules, this number starts with YMXCOUPL. The module can be software driven using this serial number. The serial number cannot be modified.

Logical name

The logical name is similar to the serial number: it is a supposedly unique character string which allows you to reference your module by software. However, in the opposite of the serial number, the logical name can be modified at will. The benefit is to enable you to build several copies of the same project without needing to modify the driving software. You only need to program the same logical name in each copy. Warning: the behavior of a project becomes unpredictable when it contains several modules with the same logical name and when the driving software tries to access one of these modules through its logical name. When leaving the factory, modules do not have an assigned logical name. It is yours to define.

2.2. Specific elements

Solid State relays

The eight solid-state relays embedded in the Yocto-MaxiCoupler module function as simples single-pole single-throw switches. It means that when they are at rest (state A), the commanded circuit is open; when the relay is active (state B), the circuit is closed. This relays can commute DC current as well as AC current. Once closed these relay have a 25 ohms resistance, which much more than a classic electromechanical relay. The maximum current these relays can commute is 0.1A ampères. Theses relays have an internal overload protection: in case of overload, their resistance increases quickly in otder to limit the current.

Relay wiring inside the module.

The $PRODNAME is only intended to be connected to safety extra low voltage (SELV) circuits. It should not be presented with voltages exceeding 60V, nor connected to mains circuits.

Leds indicating the active output

Right in front of the relays, there is a group of eight green leds which indicate which relay is active. By default, the light of these leds is rather strong, but you can change their luminosity by software.

2.3. Functional insulation

The Yocto-MaxiCoupler is designed as two distinct electrical circuits, separated by a functional insulation. This insulation plays no role for the operator safety, since both circuits of the Yocto-MaxiCoupler work with safety extra low voltages (SELV) and are accessible without risk at any time. You must be aware that this insulation is not sufficient to permit a safe use of the product in case it would be connected to the mains, or to a similar source where transiant overvoltages can be expected. Make sure not to exceed the specified voltage limit in any circumstance.

The specifications of the USB bus insulation are as follows:

• Withholding voltage³: $SPECISOUSB$
• Clearance distance: 4mm
• Creepage distance: 4mm
• Material group: Cat IIIa (FR4)

Each of the eight output circuit is electrically insulated from the others. The specifications of the insulation between channels are as follow:

• Clearance distance: 0.5mm
• Creepage distance: 0.5mm
• Material group: Cat IIIa (FR4)

2.4. Optional accessories

The accessories below are not necessary to use the Yocto-MaxiCoupler module but might be useful depending on your project. These are mostly common products that you can buy from your favorite hacking store. To save you the tedious job of looking for them, most of them are also available on the Yoctopuce shop.

Screws and spacers

In order to mount the Yocto-MaxiCoupler module, you can put small screws in the 3mm assembly holes, with a screw head no larger than 8mm. The best way is to use threaded spacers, which you can then mount wherever you want. You can find more details on this topic in the chapter about assembly and connections.

Micro-USB hub

If you intend to put several Yoctopuce modules in a very small space, you can connect them directly to a micro-USB hub. Yoctopuce builds a USB hub particularly small for this purpose (down to 20mmx36mm), on which you can directly solder a USB cable instead of using a USB plug. For more details, see the micro-USB hub information sheet.

YoctoHub-Ethernet, YoctoHub-Wireless and YoctoHub-GSM

You can add network connectivity to your Yocto-MaxiCoupler, thanks to the YoctoHub-Ethernet, the YoctoHub-Wireless and the YoctoHub-GSM which provides repectiveley Ethernet, WiFi and GSM connectivity. All of them can drive up to three devices and behave exactly like a regular computer running a VirtualHub.

1.27mm (or 1.25mm) connectors

In case you wish to connect your Yocto-MaxiCoupler to a Micro-hub USB or a YoctoHub without using a bulky USB connector, you can use the four 1.27mm pads just behind the USB connector. There are two options.

You can mount the Yocto-MaxiCoupler directly on the hub using screw and spacers, and connect it using 1.27mm board-to-board connectors. To prevent shortcuts, it is best to solder the female connector on the hub and the male connector on the Yocto-MaxiCoupler.

You can also use a small 4-wires cable with a 1.27mm connector. 1.25mm works as well, it does not make a difference for 4 pins. This makes it possible to move the device a few inches away. Don't put it too far away if you use that type of cable, because as the cable is not shielded, it may cause undesirable electromagnetic emissions.

Enclosure

Your Yocto-MaxiCoupler has been designed to be installed as is in your project. Nevertheless, Yoctopuce sells enclosures specifically designed for Yoctopuce devices. More details are available on the Yoctopuce web site ⁴. The suggested enclosure model for your Yocto-MaxiCoupler is the YoctoBox-MaxiIO-Transp.

You can install your Yocto-MaxiCoupler in an optional enclosure

3. First steps

By design, all Yoctopuce modules are driven the same way. Therefore, user's guides for all the modules of the range are very similar. If you have already carefully read through the user's guide of another Yoctopuce module, you can jump directly to the description of the module functions.

3.1. Prerequisites

In order to use your Yocto-MaxiCoupler module, you should have the following items at hand.

A computer

Yoctopuce modules are intended to be driven by a computer (or possibly an embedded microprocessor). You will write the control software yourself, according to your needs, using the information provided in this manual.

Yoctopuce provides software libraries to drive its modules for the following operating systems: Windows, macOS X, Linux, and Android. Yoctopuce modules do not require installing any specific system driver, as they leverage the standard HID driver⁵ provided with every operating system.

Windows versions currently supported are: Windows XP, Windows 2003, Windows Vista, Windows 7, Windows 8 and Windows 10. Both 32 bit and 64 bit versions are supported. The programming library is also available for the Universal Windows Platform (UWP), which is supported by all flavors of Windows 10, including Windows 10 IoT. Yoctopuce is frequently testing its modules on Windows 7 and Windows 10.

MacOS versions currently supported are: Mac OS X 10.9 (Maverick), 10.10 (Yosemite), 10.11 (El Capitan), macOS 10.12 (Sierra), macOS 10.13 (High Sierra) and macOS 10.14 (Mojave). Yoctopuce is frequently testing its modules on macOS 10.14.

Linux kernels currently supported are the 2.6 branch, the 3.x branch and the 4.x branch. Other versions of the Linux kernel, and even other UNIX variants, are very likely to work as well, as Linux support is implemented through the standard libusb API. Yoctopuce is frequently testing its modules on Linux kernel 4.15 (Ubuntu 18.04 LTS).

Android versions currently supported are: Android 3.1 and later. Moreover, it is necessary for the tablet or phone to support the Host USB mode. Yoctopuce is frequently testing its modules on Android 7.x on a Samsung Galaxy A6 with the Java for Android library.

A USB 2.0 cable, type A-micro B

USB 2.0 connectors exist in three sizes: the "standard" size that you probably use to connect your printer, the very common mini size to connect small devices, and finally the micro size often used to connect mobile phones, as long as they do not exhibit an apple logo. All USB modules manufactured by Yoctopuce use micro size connectors.

The most common USB 2.0 connectors: A, B, Mini B, Micro A, Micro B⁶

To connect your Yocto-MaxiCoupler module to a computer, you need a USB 2.0 cable of type A-micro B. The price of this cable may vary a lot depending on the source, look for it under the name USB 2.0 A to micro B Data cable. Make sure not to buy a simple USB charging cable without data connectivity. The correct type of cable is available on the Yoctopuce shop.

You must plug in your Yocto-MaxiCoupler module with a USB 2.0 cable of type A - micro B

If you insert a USB hub between the computer and the Yocto-MaxiCoupler module, make sure to take into account the USB current limits. If you do not, be prepared to face unstable behaviors and unpredictable failures. You can find more details on this topic in the chapter about assembly and connections.

3.2. Testing USB connectivity

At this point, your Yocto-MaxiCoupler should be connected to your computer, which should have recognized it. It is time to make it work.

Go to the Yoctopuce web site and download the Virtual Hub software⁷. It is available for Windows, Linux, and Mac OS X. Normally, the Virtual Hub software serves as an abstraction layer for languages which cannot access the hardware layers of your computer. However, it also offers a succinct interface to configure your modules and to test their basic functions. You access this interface with a simple web browser⁸. Start the Virtual Hub software in a command line, open your preferred web browser and enter the URL http://127.0.0.1:4444. The list of the Yoctopuce modules connected to your computer is displayed.

Module list as displayed in your web bowser

3.3. Localization

You can then physically localize each of the displayed modules by clicking on the beacon button. This puts the Yocto-led of the corresponding module in Yocto-beacon mode. It starts flashing, which allows you to easily localize it. The second effect is to display a little blue circle on the screen. You obtain the same behavior when pressing the Yocto-button of the module.

3.4. Test of the module

The first item to check is that your module is working well: click on the serial number corresponding to your module. This displays a window summarizing the properties of your Yocto-MaxiCoupler.

Properties of the Yocto-MaxiCoupler module

This window allows you, among other things, to test the relays with the switch to A / switch to B buttons. There is a characteristic clicking when a relay is working. Moreover, the led corresponding to the active output lights up. Notice that the module consumption varies according to the active outputs.

3.5. Configuration

When, in the module list, you click on the configure button corresponding to your module, the configuration window is displayed.

Yocto-MaxiCoupler module configuration.

Firmware

The module firmware can easily be updated with the help of the interface. Firmware destined for Yoctopuce modules are available as .byn files and can be downloaded from the Yoctopuce web site.

To update a firmware, simply click on the upgrade button on the configuration window and follow the instructions. If the update fails for one reason or another, unplug and re-plug the module and start the update process again. This solves the issue in most cases. If the module was unplugged while it was being reprogrammed, it does probably not work anymore and is not listed in the interface. However, it is always possible to reprogram the module correctly by using the Virtual Hub software ⁹ in command line ¹⁰.

Logical name of the module

The logical name is a name that you choose, which allows you to access your module, in the same way a file name allows you to access its content. A logical name has a maximum length of 19 characters. Authorized characters are A..Z, a..z, 0..9, _, and -. If you assign the same logical name to two modules connected to the same computer and you try to access one of them through this logical name, behavior is undetermined: you have no way of knowing which of the two modules answers.

Luminosity

This parameter allows you to act on the maximal intensity of the leds of the module. This enables you, if necessary, to make it a little more discreet, while limiting its power consumption. Note that this parameter acts on all the signposting leds of the module, including the Yocto-led. If you connect a module and no led turns on, it may mean that its luminosity was set to zero.

Logical names of functions

Each Yoctopuce module has a serial number and a logical name. In the same way, each function on each Yoctopuce module has a hardware name and a logical name, the latter can be freely chosen by the user. Using logical names for functions provides a greater flexibility when programming modules.

The only functions of the Yocto-MaxiCoupler module correspond to its embedded relays, with hardware names "relay1" to "relay8".

4. Assembly and connections

This chapter provides important information regarding the use of the Yocto-MaxiCoupler module in real-world situations. Make sure to read it carefully before going too far into your project if you want to avoid pitfalls.

4.1. Fixing

While developing your project, you can simply let the module hang at the end of its cable. Check only that it does not come in contact with any conducting material (such as your tools). When your project is almost at an end, you need to find a way for your modules to stop moving around.

Examples of assembly on supports

The Yocto-MaxiCoupler module contains 3mm assembly holes. You can use these holes for screws. The screw head diameter must not be larger than 8mm or they will damage the module circuits. Make sure that the lower surface of the module is not in contact with the support. We recommend using spacers, but other methods are possible. Nothing prevents you from fixing the module with a glue gun; it will not be good-looking, but it will hold.

4.2. Assembly examples

If you obtained this Yocto-MaxiCoupler module, it is probably because you know exactly what you intend to do with it. You can nevertheless find below a few wiring examples, among the simplest.

Drive a light bulb with your Yocto-MaxiCoupler module.

Drive two light bulbs with your Yocto-MaxiCoupler module.

4.3. USB power distribution

Although USB means Universal Serial BUS, USB devices are not physically organized as a flat bus but as a tree, using point-to-point connections. This has consequences on power distribution: to make it simple, every USB port must supply power to all devices directly or indirectly connected to it. And USB puts some limits.

In theory, a USB port provides 100mA, and may provide up to 500mA if available and requested by the device. In the case of a hub without external power supply, 100mA are available for the hub itself, and the hub should distribute no more than 100mA to each of its ports. This is it, and this is not much. In particular, it means that in theory, it is not possible to connect USB devices through two cascaded hubs without external power supply. In order to cascade hubs, it is necessary to use self-powered USB hubs, that provide a full 500mA to each subport.

In practice, USB would not have been as successful if it was really so picky about power distribution. As it happens, most USB hub manufacturers have been doing savings by not implementing current limitation on ports: they simply connect the computer power supply to every port, and declare themselves as self-powered hub even when they are taking all their power from the USB bus (in order to prevent any power consumption check in the operating system). This looks a bit dirty, but given the fact that computer USB ports are usually well protected by a hardware current limitation around 2000mA, it actually works in every day life, and seldom makes hardware damage.

What you should remember: if you connect Yoctopuce modules through one, or more, USB hub without external power supply, you have no safe-guard and you depend entirely on your computer manufacturer attention to provide as much current as possible on the USB ports, and to detect overloads before they lead to problems or to hardware damages. When modules are not provided enough current, they may work erratically and create unpredictable bugs. If you want to prevent any risk, do not cascade hubs without external power supply, and do not connect peripherals requiring more than 100mA behind a bus-powered hub.

In order to help you controlling and planning overall power consumption for your project, all Yoctopuce modules include a built-in current sensor that indicates (with 5mA precision) the consumption of the module on the USB bus.

Note also that the USB cable itself may also cause power supply issues, in particular when the wires are too thin or when the cable is too long ¹¹. Good cables are usually made using AWG 26 or AWG 28 wires for data lines and AWG 24 wires for power.

4.4. Electromagnetic compatibility (EMI)

Connection methods to integrate the Yocto-MaxiCoupler obviously have an impact on the system overall electromagnetic emissions, and therefore also impact the conformity with international standards.

When we perform reference measurements to validate the conformity of our products with IEC CISPR 11, we do not use any enclosure but connect the devices using a shielded USB cable, compliant with USB 2.0 specifications: the cable shield is connected to both connector shells, and the total resistance from shell to shell is under 0.6Ω. The USB cable length is 3m, in order to expose one meter horizontally, one meter vertically and keep the last meter close to the host computer within a ferrite bead.

If you use a non-shielded USB cable, or an improperly shielded cable, your system will work perfectly well but you may not remain in conformity with the emission standard. If you are building a system made of multiple devices connected using 1.27mm pitch connectors, or with a sensor moved away from the device CPU, you can generally recover the conformity by using a metallic enclosure acting as an external shield.

Still on the topic of electromagnetic compatibility, the maximum supported length of the USB cable is 3m. In addition to the voltage drop issue mentionned above, using longer wires would require to run extra tests to assert compatibility with the electromagnetic immunity standards.

5. Programming, general concepts

The Yoctopuce API was designed to be at the same time simple to use and sufficiently generic for the concepts used to be valid for all the modules in the Yoctopuce range, and this in all the available programming languages. Therefore, when you have understood how to drive your Yocto-MaxiCoupler with your favorite programming language, learning to use another module, even with a different language, will most likely take you only a minimum of time.

5.1. Programming paradigm

The Yoctopuce API is object oriented. However, for simplicity's sake, only the basics of object programming were used. Even if you are not familiar with object programming, it is unlikely that this will be a hinderance for using Yoctopuce products. Note that you will never need to allocate or deallocate an object linked to the Yoctopuce API: it is automatically managed.

There is one class per Yoctopuce function type. The name of these classes always starts with a Y followed by the name of the function, for example YTemperature, YRelay, YPressure, etc.. There is also a YModule class, dedicated to managing the modules themselves, and finally there is the static YAPI class, that supervises the global workings of the API and manages low level communications.

Structure of the Yoctopuce API.

The YSensor class

Each Yoctopuce sensor function has its dedicated class: YTemperature to measure the temperature, YVoltage to measure a voltage, YRelay to drive a relay, etc. However there is a special class that can do more: YSensor.

The YSensor class is the parent class for all Yoctopuce sensors, and can provide access to any sensor, regardless of its type. It includes methods to access all common functions. This makes it easier to create applications that use many different sensors. Moreover, if you create an application based on YSensor, it will work with all Yoctopuce sensors, even those which do no yet exist.

Programmation

In the Yoctopuce API, priority was put on the ease of access to the module functions by offering the possibility to make abstractions of the modules implementing them. Therefore, it is quite possible to work with a set of functions without ever knowing exactly which module are hosting them at the hardware level. This tremendously simplifies programming projects with a large number of modules.

From the programming stand point, your Yocto-MaxiCoupler is viewed as a module hosting a given number of functions. In the API, these functions are objects which can be found independently, in several ways.

Access to the functions of a module

Access by logical name

Each function can be assigned an arbitrary and persistent logical name: this logical name is stored in the flash memory of the module, even if this module is disconnected. An object corresponding to an Xxx function to which a logical name has been assigned can then be directly found with this logical name and the YXxx.FindXxx method. Note however that a logical name must be unique among all the connected modules.

Access by enumeration

You can enumerate all the functions of the same type on all the connected modules with the help of the classic enumeration functions FirstXxx and nextXxxx available for each YXxx class.

Access by hardware name

Each module function has a hardware name, assigned at the factory and which cannot be modified. The functions of a module can also be found directly with this hardware name and the YXxx.FindXxx function of the corresponding class.

Difference between Find and First

The YXxx.FindXxxx and YXxx.FirstXxxx methods do not work exactly the same way. If there is no available module, YXxx.FirstXxxx returns a null value. On the opposite, even if there is no corresponding module, YXxx.FindXxxx returns a valid object, which is not online but which could become so if the corresponding module is later connected.

Function handling

When the object corresponding to a function is found, its methods are available in a classic way. Note that most of these subfunctions require the module hosting the function to be connected in order to be handled. This is generally not guaranteed, as a USB module can be disconnected after the control software has started. The isOnline method, available in all the classes, is then very helpful.

Access to the modules

Even if it is perfectly possible to build a complete project while making a total abstraction of which function is hosted on which module, the modules themselves are also accessible from the API. In fact, they can be handled in a way quite similar to the functions. They are assigned a serial number at the factory which allows you to find the corresponding object with YModule.Find(). You can also assign arbitrary logical names to the modules to make finding them easier. Finally, the YModule class contains the YModule.FirstModule() and nextModule() enumeration methods allowing you to list the connected modules.

Functions/Module interaction

From the API standpoint, the modules and their functions are strongly uncorrelated by design. Nevertheless, the API provides the possibility to go from one to the other. Thus, the get_module() method, available for each function class, allows you to find the object corresponding to the module hosting this function. Inversely, the YModule class provides several methods allowing you to enumerate the functions available on a module.

5.2. The Yocto-MaxiCoupler module

The Yocto-MaxiCoupler module provides eight instances of the Relay function, corresponding to the eight photocouplers present on the module.

module : Module

attribute	type	modifiable ?
productName	String	read-only
serialNumber	String	read-only
logicalName	String	modifiable
productId	Hexadecimal number	read-only
productRelease	Hexadecimal number	read-only
firmwareRelease	String	read-only
persistentSettings	Enumerated	modifiable
luminosity	0..100%	modifiable
beacon	On/Off	modifiable
upTime	Time	read-only
usbCurrent	Used current (mA)	read-only
rebootCountdown	Integer	modifiable
userVar	Integer	modifiable

relay1 : Relay
relay2 : Relay
relay3 : Relay
relay4 : Relay
relay5 : Relay
relay6 : Relay
relay7 : Relay
relay8 : Relay

attribute	type	modifiable ?
logicalName	String	modifiable
advertisedValue	String	modifiable
state	A/B	modifiable
stateAtPowerOn	Enumerated	modifiable
maxTimeOnStateA	Time	modifiable
maxTimeOnStateB	Time	modifiable
output	On/Off	modifiable
pulseTimer	Time	modifiable
delayedPulseTimer	Aggregate	modifiable
countdown	Time	read-only

5.3. Module control interface

This interface is identical for all Yoctopuce USB modules. It can be used to control the module global parameters, and to enumerate the functions provided by each module.

productName

Character string containing the commercial name of the module, as set by the factory.

serialNumber

Character string containing the serial number, unique and programmed at the factory. For a Yocto-MaxiCoupler module, this serial number always starts with YMXCOUPL. You can use the serial number to access a given module by software.

logicalName

Character string containing the logical name of the module, initially empty. This attribute can be modified at will by the user. Once initialized to an non-empty value, it can be used to access a given module. If two modules with the same logical name are in the same project, there is no way to determine which one answers when one tries accessing by logical name. The logical name is limited to 19 characters among A..Z,a..z,0..9,_, and -.

productId

USB device identifier of the module, preprogrammed to 49 at the factory.

productRelease

Release number of the module hardware, preprogrammed at the factory.

firmwareRelease

Release version of the embedded firmware, changes each time the embedded software is updated.

persistentSettings

State of persistent module settings: loaded from flash memory, modified by the user or saved to flash memory.

luminosity

Lighting strength of the informative leds (e.g. the Yocto-Led) contained in the module. It is an integer value which varies between 0 (leds turned off) and 100 (maximum led intensity). The default value is 50. To change the strength of the module leds, or to turn them off completely, you only need to change this value.

beacon

Activity of the localization beacon of the module.

upTime

Time elapsed since the last time the module was powered on.

usbCurrent

Current consumed by the module on the USB bus, in milli-amps.

rebootCountdown

Countdown to use for triggering a reboot of the module.

userVar

32bit integer variable available for user storage.

5.4. Relay function interface

The Yoctopuce application programming interface allows you to switch the relay state. This change is not persistent: the relay will automatically return to its idle position whenever power is lost or if the module is restarted. The library can also generate automatically short pulses of determined duration. On devices with two output for each relay (double throw), the two outputs are named A and B, with output A corresponding to the idle position (at power off) and the output B corresponding to the active state. If you prefer the alternate default state, simply switch your cables on the board.

logicalName

Character string containing the logical name of the relay, initially empty. This attribute can be modified at will by the user. Once initialized to an non-empty value, it can be used to access the relay directly. If two relays with the same logical name are used in the same project, there is no way to determine which one answers when one tries accessing by logical name. The logical name is limited to 19 characters among A..Z,a..z,0..9,_, and -.

advertisedValue

Short character string summarizing the current state of the relay, that will be automatically advertised up to the parent hub. For a relay, the advertised value is the the relays state (A for the idle position, B for the active position).

state

Active output of the relays: A for the idle position, B for the active position.

stateAtPowerOn

Active output of the relays at device power on: A for the idle position, B for the active position, UNCHANGED to leave the relay as is.

maxTimeOnStateA

Maximum time (ms) allowed for relays to stay in state A before automatically switching back in to B state. Zéro means no maximum time.

maxTimeOnStateB

Maximum time (ms) allowed for relays to stay in state B before automatically switching back in to A state. Zéro means no maximum time.

output

Output state of the relays, when used as a simple switch (single throw).

pulseTimer

Time during which the relays should be kept in state B (active) before returning automatically to state A (idle state). Any explicit state change issued afterwards will cancel the automated switch.

delayedPulseTimer

Delayed pulse parameters.

countdown

Waiting delay before next pulse (delayed pulse case).

5.5. What interface: Native, DLL or Service ?

There are several methods to control you Yoctopuce module by software.

Native control

In this case, the software driving your project is compiled directly with a library which provides control of the modules. Objectively, it is the simplest and most elegant solution for the end user. The end user then only needs to plug the USB cable and run your software for everything to work. Unfortunately, this method is not always available or even possible.

The application uses the native library to control the locally connected module

Native control by DLL

Here, the main part of the code controlling the modules is located in a DLL. The software is compiled with a small library which provides control of the DLL. It is the fastest method to code module support in a given language. Indeed, the "useful" part of the control code is located in the DLL which is the same for all languages: the effort to support a new language is limited to coding the small library which controls the DLL. From the end user stand point, there are few differences: one must simply make sure that the DLL is installed on the end user's computer at the same time as the main software.

The application uses the DLL to natively control the locally connected module

Control by service

Some languages do simply not allow you to easily gain access to the hardware layers of the machine. It is the case for Javascript, for instance. To deal with this case, Yoctopuce provides a solution in the form of a small piece of software called VirtualHub¹². It can access the modules, and your application only needs to use a library which offers all necessary functions to control the modules via this VirtualHub. The end users will have to start the VirtualHub before running the project control software itself, unless they decide to install the hub as a service/deamon, in which case the VirtualHub starts automatically when the machine starts up.

The application connects itself to the VirtualHub to gain access to the module

The service control method comes with a non-negligible advantage: the application does not need to run on the machine on which the modules are connected. The application can very well be located on another machine which connects itself to the service to drive the modules. Moreover, the native libraries and DLL mentioned above are also able to connect themselves remotely to one or several machines running VirtualHub.

When a VirtualHub is used, the control application does not need to reside on the same machine as the module.

Whatever the selected programming language and the control paradigm used, programming itself stays strictly identical. From one language to another, functions bear exactly the same name, and have the same parameters. The only differences are linked to the constraints of the languages themselves.

Language	Native	Native with DLL	Virtual hub
C++	✔	✔	✔
Objective-C	✔	-	✔
Delphi	-	✔	✔
Python	-	✔	✔
VisualBasic .Net	-	✔	✔
C# .Net	-	✔	✔
C# UWP	✔	-	✔
EcmaScript / JavaScript	-	-	✔
PHP	-	-	✔
Java	-	✔	✔
Java for Android	✔	-	✔
Command line	✔	-	✔

Support methods for different languages

Limitations of the Yoctopuce libraries

Natives et DLL libraries have a technical limitation. On the same computer, you cannot concurrently run several applications accessing Yoctopuce devices directly. If you want to run several projects on the same computer, make sure your control applications use Yoctopuce devices through a VirtualHub software. The modification is trivial: it is just a matter of parameter change in the yRegisterHub() call.

5.6. Programming, where to start?

At this point of the user's guide, you should know the main theoretical points of your Yocto-MaxiCoupler. It is now time to practice. You must download the Yoctopuce library for your favorite programming language from the Yoctopuce web site¹³. Then skip directly to the chapter corresponding to the chosen programming language.

All the examples described in this guide are available in the programming libraries. For some languages, the libraries also include some complete graphical applications, with their source code.

When you have mastered the basic programming of your module, you can turn to the chapter on advanced programming that describes some techniques that will help you make the most of your Yocto-MaxiCoupler.

6. Using the Yocto-MaxiCoupler in command line

When you want to perform a punctual operation on your Yocto-MaxiCoupler, such as reading a value, assigning a logical name, and so on, you can obviously use the Virtual Hub, but there is a simpler, faster, and more efficient method: the command line API.

The command line API is a set of executables, one by type of functionality offered by the range of Yoctopuce products. These executables are provided pre-compiled for all the Yoctopuce officially supported platforms/OS. Naturally, the executable sources are also provided¹⁴.

6.1. Installing

Download the command line API¹⁵. You do not need to run any setup, simply copy the executables corresponding to your platform/OS in a directory of your choice. You may add this directory to your PATH variable to be able to access these executables from anywhere. You are all set, you only need to connect your Yocto-MaxiCoupler, open a shell, and start working by typing for example:

To use the command API on Linux, you need either have root privileges or to define an udev rule for your system. See the Troubleshooting chapter for more details.

6.2. Use: general description

All the command line API executables work on the same principle. They must be called the following way

[options] manage the global workings of the commands, they allow you, for instance, to pilot a module remotely through the network, or to force the module to save its configuration after executing the command.

[target] is the name of the module or of the function to which the command applies. Some very generic commands do not need a target. You can also use the aliases "any" and "all", or a list of names separated by comas without space.

command is the command you want to run. Almost all the functions available in the classic programming APIs are available as commands. You need to respect neither the case nor the underlined characters in the command name.

[parameters] logically are the parameters needed by the command.

At any time, the command line API executables can provide a rather detailed help. Use for instance:

to know the list of available commands for a given command line API executable, or even:

to obtain a detailed description of the parameters of a command.

6.3. Control of the Relay function

To control the Relay function of your Yocto-MaxiCoupler, you need the YRelay executable file.

For instance, you can launch:

This example uses the "any" target to indicate that we want to work on the first Relay function found among all those available on the connected Yoctopuce modules when running. This prevents you from having to know the exact names of your function and of your module.

But you can use logical names as well, as long as you have configured them beforehand. Let us imagine a Yocto-MaxiCoupler module with the YMXCOUPL-123456 serial number which you have called "MyModule", and its relay1 function which you have renamed "MyFunction". The five following calls are strictly equivalent (as long as MyFunction is defined only once, to avoid any ambiguity).

To work on all the Relay functions at the same time, use the "all" target.

For more details on the possibilities of the YRelay executable, use:

6.4. Control of the module part

Each module can be controlled in a similar way with the help of the YModule executable. For example, to obtain the list of all the connected modules, use:

You can also use the following command to obtain an even more detailed list of the connected modules:

Each xxx property of the module can be obtained thanks to a command of the get_xxxx() type, and the properties which are not read only can be modified with the set_xxx() command. For example:

Changing the settings of the module

When you want to change the settings of a module, simply use the corresponding set_xxx command. However, this change happens only in the module RAM: if the module restarts, the changes are lost. To store them permanently, you must tell the module to save its current configuration in its nonvolatile memory. To do so, use the saveToFlash command. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash method. For example:

Note that you can do the same thing in a single command with the -s option.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

6.5. Limitations

The command line API has the same limitation than the other APIs: there can be only one application at a given time which can access the modules natively. By default, the command line API works in native mode.

You can easily work around this limitation by using a Virtual Hub: run the VirtualHub¹⁶ on the concerned machine, and use the executables of the command line API with the -r option. For example, if you use:

you obtain a list of the modules connected by USB, using a native access. If another command which accesses the modules natively is already running, this does not work. But if you run a Virtual Hub, and you give your command in the form:

it works because the command is not executed natively anymore, but through the Virtual Hub. Note that the Virtual Hub counts as a native application.

7. Using Yocto-MaxiCoupler with JavaScript / EcmaScript

EcmaScript is the official name of the standardized version of the web-oriented programming language commonly referred to as JavaScript. This Yoctopuce library take advantages of advanced features introduced in EcmaScript 2017. It has therefore been named Library for JavaScript / EcmaScript 2017 to differentiate it from the previous Library for JavaScript, now deprecated in favor of this new version.

This library provides access to Yoctopuce devices for modern JavaScript engines. It can be used within a browser as well as with Node.js. The library will automatically detect upon initialization whether the runtime environment is a browser or a Node.js virtual machine, and use the most appropriate system libraries accordingly.

Asynchronous communication with the devices is handled across the whole library using Promise objects, leveraging the new EcmaScript 2017 async / await non-blocking syntax for asynchronous I/O (see below). This syntax is now available out-of-the-box in most Javascript engines. No transpilation is needed: no Babel, no jspm, just plain Javascript. Here is your favorite engines minimum version needed to run this code. All of them are officially released at the time we write this document.

• Node.js v7.6 and later
• Firefox 52
• Opera 42 (incl. Android version)
• Chrome 55 (incl. Android version)
• Safari 10.1 (incl. iOS version)
• Android WebView 55
• Google V8 Javascript engine v5.5

If you need backward-compatibility with older releases, you can always run Babel to transpile your code and the library to older standards, as described a few paragraphs below.

We don't suggest using jspm 0.17 anymore since that tool is still in Beta after 18 month, and having to use an extra tool to implement our library is pointless now that async / await are part of the standard.

7.1. Blocking I/O versus Asynchronous I/O in JavaScript

JavaScript is single-threaded by design. That means, if a program is actively waiting for the result of a network-based operation such as reading from a sensor, the whole program is blocked. In browser environments, this can even completely freeze the user interface. For this reason, the use of blocking I/O in JavaScript is strongly discouraged nowadays, and blocking network APIs are getting deprecated everywhere.

Instead of using parallel threads, JavaScript relies on asynchronous I/O to handle operations with a possible long timeout: whenever a long I/O call needs to be performed, it is only triggered and but then the code execution flow is terminated. The JavaScript engine is therefore free to handle other pending tasks, such as UI. Whenever the pending I/O call is completed, the system invokes a callback function with the result of the I/O call to resume execution of the original execution flow.

When used with plain callback functions, as pervasive in Node.js libraries, asynchronous I/O tend to produce code with poor readability, as the execution flow is broken into many disconnected callback functions. Fortunately, new methods have emerged recently to improve that situation. In particular, the use of Promise objects to abstract and work with asynchronous tasks helps a lot. Any function that makes a long I/O operation can return a Promise, which can be used by the caller to chain subsequent operations in the same flow. Promises are part of EcmaScript 2015 standard.

Promise objects are good, but what makes them even better is the new async / await keywords to handle asynchronous I/O:

• a function declared async will automatically encapsulate its result as a Promise
• within an async function, any function call prefixed with by await will chain the Promise returned by the function with a promise to resume execution of the caller
• any exception during the execution of an async function will automatically invoke the Promise failure continuation

Long story made short, async and await make it possible to write EcmaScript code with all benefits of asynchronous I/O, but without breaking the code flow. It is almost like multi-threaded execution, except that control switch between pending tasks only happens at places where the await keyword appears.

We have therefore chosen to write our new EcmaScript library using Promises and async functions, so that you can use the friendly await syntax. To keep it easy to remember, all public methods of the EcmaScript library are async, i.e. return a Promise object, except:

• GetTickCount(), because returning a time stamp asynchronously does not make sense...
• FindModule(), FirstModule(), nextModule(), ... because device detection and enumeration always work on internal device lists handled in background, and does not require immediate asynchronous I/O.

7.2. Using Yoctopuce library for JavaScript / EcmaScript 2017

JavaScript is one of those languages which do not generally allow you to directly access the hardware layers of your computer. Therefore the library can only be used to access network-enabled devices (connected through a YoctoHub), or USB devices accessible through Yoctopuce TCP/IP to USB gateway, named VirtualHub.

Go to the Yoctopuce web site and download the following items:

• The Javascript / EcmaScript 2017 programming library¹⁷
• The VirtualHub software¹⁸ for Windows, Mac OS X or Linux, depending on your OS

Extract the library files in a folder of your choice, you will find many of examples in it. Connect your modules and start the VirtualHub software. You do not need to install any driver.

Using the official Yoctopuce library for node.js

Start by installing the latest Node.js version (v7.6 or later) on your system. It is very easy. You can download it from the official web site: http://nodejs.org. Make sure to install it fully, including npm, and add it to the system path.

To give it a try, go into one of the example directory (for instance example_nodejs/Doc-Inventory). You will see that it include an application description file (package.json) and a source file (demo.js). To download and setup the libraries needed by this example, just run:

Once done, you can start the example file using:

Using a local copy of the Yoctopuce library with node.js

If for some reason you need to make changes to the Yoctopuce library, you can easily configure your project to use the local copy in the lib/ subdirectory rather than the official npm package. In order to do so, simply type the following command in your project directory:

Using the Yoctopuce library within a browser (HTML)

For HTML examples, it is even simpler: there is nothing to install. Each example is a single HTML file that you can open in a browser to try it. In this context, loading the Yoctopuce library is no different from any standard HTML script include tag.

Using the Yoctoluce library on older JavaScript engines

If you need to run this library on older JavaScript engines, you can use Babel¹⁹ to transpile your code and the library into older JavaScript standards. To install Babel with typical settings, simply use:

You would typically ask Babel to put the transpiled files in another directory, named compat for instance. Your files and all files of the Yoctopuce library should be transpiled, as follow:

Although this approach is based on node.js toolchain, it actually works as well for transpiling JavaScript files for use in a browser. The only thing that you cannot do so easily is transpiling JavaScript code embedded directly in an HTML page. You have to use an external script file for using EcmaScript 2017 syntax with Babel.

Babel has many smart features, such as a watch mode that will automatically refresh transpiled files whenever the source file is changed, but this is beyond the scope of this note. You will find more in Babel documentation.

Backward-compatibility with the old JavaScript library

This new library is not fully backward-compatible with the old JavaScript library, because there is no way to transparently map the old blocking API to the new asynchronous API. The method names however are the same, and old synchronous code can easily be made asynchronous just by adding the proper await keywords before the method calls. For instance, simply replace:

by

Apart from a few exceptions, most XXX_async redundant methods have been removed as well, as they would have introduced confusion on the proper way of handling asynchronous behaviors. It is however very simple to get an async method to invoke a callback upon completion, using the returned Promise object. For instance, you can replace:

by

In some cases, it might be desirable to get a sensor value using a method identical to the old synchronous methods (without using Promises), even if it returns a slightly outdated cached value since I/O is not possible. For this purpose, the EcmaScript library introduce new classes called synchronous proxies. A synchronous proxy is an object that mirrors the most recent state of the connected class, but can be read using regular synchronous function calls. For instance, instead of writing:

you can use:

You can also rewrite this last asynchronous call as:

7.3. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a JavaScript code snipplet to use the Relay function.

Let us look at these lines in more details.

yocto_api and yocto_relay import

These two import provide access to functions allowing you to manage Yoctopuce modules. yocto_api is always needed, yocto_relay is necessary to manage modules containing a relay, such as Yocto-MaxiCoupler. Other imports can be useful in other cases, such as YModule which can let you enumerate any type of Yoctopuce device.

YAPI.RegisterHub

The RegisterHub method allows you to indicate on which machine the Yoctopuce modules are located, more precisely on which machine the VirtualHub software is running. In our case, the 127.0.0.1:4444 address indicates the local machine, port 4444 (the standard port used by Yoctopuce). You can very well modify this address, and enter the address of another machine on which the VirtualHub software is running, or of a YoctoHub. If the host cannot be reached, this function will trigger an exception.

YRelay.FindRelay

The FindRelay method allows you to find a relay from the serial number of the module on which it resides and from its function name. You can also use logical names, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

YRelay.FindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by FindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

A real example, for Node.js

Open a command window (a terminal, a shell...) and go into the directory example_nodejs/Doc-GettingStarted-Yocto-MaxiCoupler within Yoctopuce library for JavaScript / EcmaScript 2017. In there, you will find a file named demo.js with the sample code below, which uses the functions explained above, but this time used with all side materials needed to make it work nicely as a small demo.

If your Yocto-MaxiCoupler is not connected on the host running the browser, replace in the example the address 127.0.0.1 by the IP address of the host on which the Yocto-MaxiCoupler is connected and where you run the VirtualHub.

As explained at the beginning of this chapter, you need to have Node.js v7.6 or later installed to try this example. When done, you can type the following two commands to automatically download and install the dependencies for building this example:

You can the start the sample code within Node.js using the following command, replacing the [...] by the arguments that you want to pass to the demo code:

Same example, but this time running in a browser

If you want to see how to use the library within a browser rather than with Node.js, switch to the directory example_html/Doc-GettingStarted-Yocto-MaxiCoupler. You will find there a single HTML file, with a JavaScript section similar to the code above, but with a few changes since it has to interact through an HTML page rather than through the JavaScript console.

No installation is needed to run this example, all you have to do is open the HTML file using a web browser,

7.4. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type get_xxxx(), and properties which are not read-only can be modified with the help of the set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the YModule.FirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not null. Below a short example listing the connected modules.

7.5. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

8. Using Yocto-MaxiCoupler with PHP

PHP is, like Javascript, an atypical language when interfacing with hardware is at stakes. Nevertheless, using PHP with Yoctopuce modules provides you with the opportunity to very easily create web sites which are able to interact with their physical environment, and this is not available to every web server. This technique has a direct application in home automation: a few Yoctopuce modules, a PHP server, and you can interact with your home from anywhere on the planet, as long as you have an internet connection.

PHP is one of those languages which do not allow you to directly access the hardware layers of your computer. Therefore you need to run a virtual hub on the machine on which your modules are connected.

To start your tests with PHP, you need a PHP 5.3 (or more) server²⁰, preferably locally on you machine. If you wish to use the PHP server of your internet provider, it is possible, but you will probably need to configure your ADSL router for it to accept and forward TCP request on the 4444 port.

8.1. Getting ready

Go to the Yoctopuce web site and download the following items:

• The PHP programming library²¹
• The VirtualHub software²² for Windows, Mac OS X, or Linux, depending on your OS

Decompress the library files in a folder of your choice accessible to your web server, connect your modules, run the VirtualHub software, and you are ready to start your first tests. You do not need to install any driver.

8.2. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a PHP code snipplet to use the Relay function.

Let's look at these lines in more details.

yocto_api.php and yocto_relay.php

These two PHP includes provides access to the functions allowing you to manage Yoctopuce modules. yocto_api.php must always be included, yocto_relay.php is necessary to manage modules containing a relay, such as Yocto-MaxiCoupler.

yRegisterHub

The yRegisterHub function allows you to indicate on which machine the Yoctopuce modules are located, more precisely on which machine the VirtualHub software is running. In our case, the 127.0.0.1:4444 address indicates the local machine, port 4444 (the standard port used by Yoctopuce). You can very well modify this address, and enter the address of another machine on which the VirtualHub software is running.

yFindRelay

The yFindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

yFindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by yFindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by yFindRelay switches the relay position to one of its two outputs. The two possible parameter values are Y_STATE_A for output A, and Y_STATE_B for output B.

A real example

Open your preferred text editor²³, copy the code sample below, save it with the Yoctopuce library files in a location which is accessible to you web server, then use your preferred web browser to access this page. The code is also provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

In this example, you will recognize the functions explained above, but this time used with all side materials needed to make it work nicely as a small demo.

8.3. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type get_xxxx(), and properties which are not read-only can be modified with the help of the set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not NULL. Below a short example listing the connected modules.

8.4. HTTP callback API and NAT filters

The PHP library is able to work in a specific mode called HTTP callback Yocto-API. With this mode, you can control Yoctopuce devices installed behind a NAT filter, such as a DSL router for example, and this without needing to open a port. The typical application is to control Yoctopuce devices, located on a private network, from a public web site.

The NAT filter: advantages and disadvantages

A DSL router which translates network addresses (NAT) works somewhat like a private phone switchboard (a PBX): internal extensions can call each other and call the outside; but seen from the outside, there is only one official phone number, that of the switchboard itself. You cannot reach the internal extensions from the outside.

Typical DSL configuration: LAN machines are isolated from the outside by the DSL router

Transposed to the network, we have the following: appliances connected to your home automation network can communicate with one another using a local IP address (of the 192.168.xxx.yyy type), and contact Internet servers through their public address. However, seen from the outside, you have only one official IP address, assigned to the DSL router only, and you cannot reach your network appliances directly from the outside. It is rather restrictive, but it is a relatively efficient protection against intrusions.

Responses from request from LAN machines are routed.

But requests from the outside are blocked.

Seeing Internet without being seen provides an enormous security advantage. However, this signifies that you cannot, a priori, set up your own web server at home to control a home automation installation from the outside. A solution to this problem, advised by numerous home automation system dealers, consists in providing outside visibility to your home automation server itself, by adding a routing rule in the NAT configuration of the DSL router. The issue of this solution is that it exposes the home automation server to external attacks.

The HTTP callback API solves this issue without having to modify the DSL router configuration. The module control script is located on an external site, and it is the VirtualHub which is in charge of calling it a regular intervals.

The HTTP callback API uses the VirtualHub which initiates the requests.

Configuration

The callback API thus uses the VirtualHub as a gateway. All the communications are initiated by the VirtualHub. They are thus outgoing communications and therefore perfectly authorized by the DSL router.

You must configure the VirtualHub so that it calls the PHP script on a regular basis. To do so:

1. Launch a VirtualHub
2. Access its interface, usually 127.0.0.1:4444
3. Click on the configure button of the line corresponding to the VirtualHub itself
4. Click on the edit button of the Outgoing callbacks section

Click on the "configure" button on the first line

Click on the "edit" button of the "Outgoing callbacks" section

And select "Yocto-API callback".

You then only need to define the URL of the PHP script and, if need be, the user name and password to access this URL. Supported authentication methods are basic and digest. The second method is safer than the first one because it does not allow transfer of the password on the network.

Usage

From the programmer standpoint, the only difference is at the level of the yRegisterHub function call. Instead of using an IP address, you must use the callback string (or http://callback which is equivalent).

The remainder of the code stays strictly identical. On the VirtualHub interface, at the bottom of the configuration window for the HTTP callback API , there is a button allowing you to test the call to the PHP script.

Be aware that the PHP script controlling the modules remotely through the HTTP callback API can be called only by the VirtualHub. Indeed, it requires the information posted by the VirtualHub to function. To code a web site which controls Yoctopuce modules interactively, you must create a user interface which stores in a file or in a database the actions to be performed on the Yoctopuce modules. These actions are then read and run by the control script.

Common issues

For the HTTP callback API to work, the PHP option allow_url_fopen must be set. Some web site hosts do not set it by default. The problem then manifests itself with the following error:

error: URL file-access is disabled in the server configuration

To set this option, you must create, in the repertory where the control PHP script is located, an .htaccess file containing the following line:
php_flag "allow_url_fopen" "On"
Depending on the security policies of the host, it is sometimes impossible to authorize this option at the root of the web site, or even to install PHP scripts receiving data from a POST HTTP. In this case, place the PHP script in a subdirectory.

Limitations

This method that allows you to go through NAT filters cheaply has nevertheless a price. Communications being initiated by the VirtualHub at a more or less regular interval, reaction time to an event is clearly longer than if the Yoctopuce modules were driven directly. You can configure the reaction time in the specific window of the VirtualHub, but it is at least of a few seconds in the best case.

The HTTP callback Yocto-API mode is currently available in PHP, EcmaScript (Node.JS) and Java only.

8.5. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

9. Using Yocto-MaxiCoupler with C++

C++ is not the simplest language to master. However, if you take care to limit yourself to its essential functionalities, this language can very well be used for short programs quickly coded, and it has the advantage of being easily ported from one operating system to another. Under Windows, all the examples and the project models are tested with Microsoft Visual Studio 2010 Express, freely available on the Microsoft web site²⁴. Under Mac OS X, all the examples and project models are tested with XCode 4, available on the App Store. Moreover, under Max OS X and under Linux, you can compile the examples using a command line with GCC using the provided GNUmakefile. In the same manner under Windows, a Makefile allows you to compile examples using a command line, fully knowing the compilation and linking arguments.

Yoctopuce C++ libraries²⁵ are integrally provided as source files. A section of the low-level library is written in pure C, but you should not need to interact directly with it: everything was done to ensure the simplest possible interaction from C++. The library is naturally also available as binary files, so that you can link it directly if you prefer.

You will soon notice that the C++ API defines many functions which return objects. You do not need to deallocate these objects yourself, the API does it automatically at the end of the application.

In order to keep them simple, all the examples provided in this documentation are console applications. Naturally, the libraries function in a strictly identical manner if you integrate them in an application with a graphical interface. You will find in the last section of this chapter all the information needed to create a wholly new project linked with the Yoctopuce libraries.

9.1. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a C++ code snipplet to use the Relay function.

Let's look at these lines in more details.

yocto_api.h et yocto_relay.h

These two include files provide access to the functions allowing you to manage Yoctopuce modules. yocto_api.h must always be used, yocto_relay.h is necessary to manage modules containing a relay, such as Yocto-MaxiCoupler.

yRegisterHub

The yRegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. When used with the parameter "usb", it will use the modules locally connected to the computer running the library. If the initialization does not succeed, this function returns a value different from YAPI_SUCCESS and errmsg contains the error message.

yFindRelay

The yFindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

yFindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by yFindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by yFindRelay switches the relay position to one of its two outputs. The two possible parameter values are Y_STATE_A for output A, and Y_STATE_B for output B.

A real example

Launch your C++ environment and open the corresponding sample project provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library. If you prefer to work with your favorite text editor, open the file main.cpp, and type make to build the example when you are done.

In this example, you will recognize the functions explained above, but this time used with all side materials needed to make it work nicely as a small demo.

9.2. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type get_xxxx(), and properties which are not read-only can be modified with the help of the set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not NULL. Below a short example listing the connected modules.

9.3. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

9.4. Integration variants for the C++ Yoctopuce library

Depending on your needs and on your preferences, you can integrate the library into your projects in several distinct manners. This section explains how to implement the different options.

Integration in source format

Integrating all the sources of the library into your projects has several advantages:

• It guaranties the respect of the compilation conventions of your project (32/64 bits, inclusion of debugging symbols, unicode or ASCII characters, etc.);
• It facilitates debugging if you are looking for the cause of a problem linked to the Yoctopuce library;
• It reduces the dependencies on third party components, for example in the case where you would need to recompile this project for another architecture in many years;
• It does not require the installation of a dynamic library specific to Yoctopuce on the final system, everything is in the executable.

To integrate the source code, the easiest way is to simply include the Sources directory of your Yoctopuce library into your IncludePath, and to add all the files of this directory (including the sub-directory yapi) to your project.

For your project to build correctly, you need to link with your project the prerequisite system libraries, that is:

• For Windows: the libraries are added automatically
• For Mac OS X: IOKit.framework and CoreFoundation.framework
• For Linux: libm, libpthread, libusb1.0, and libstdc++

Integration as a static library

Integration of the Yoctopuce library as a static library is a simpler manner to build a small executable which uses Yoctopuce modules. You can quickly compile the program with a single command. You do not need to install a dynamic library specific to Yoctopuce, everything is in the executable.

To integrate the static Yoctopuce library to your project, you must include the Sources directory of the Yoctopuce library into your IncludePath, and add the sub-directory Binaries/... corresponding to your operating system into your libPath.

Then, for you project to build correctly, you need to link with your project the Yoctopuce library and the prerequisite system libraries:

• For Windows: yocto-static.lib
• For Mac OS X: libyocto-static.a, IOKit.framework, and CoreFoundation.framework
• For Linux: libyocto-static.a, libm, libpthread, libusb1.0, and libstdc++.

Note, under Linux, if you wish to compile in command line with GCC, it is generally advisable to link system libraries as dynamic libraries, rather than as static ones. To mix static and dynamic libraries on the same command line, you must pass the following arguments:

gcc (...) -Wl,-Bstatic -lyocto-static -Wl,-Bdynamic -lm -lpthread -lusb-1.0 -lstdc++

Integration as a dynamic library

Integration of the Yoctopuce library as a dynamic library allows you to produce an executable smaller than with the two previous methods, and to possibly update this library, if a patch reveals itself necessary, without needing to recompile the source code of the application. On the other hand, it is an integration mode which systematically requires you to copy the dynamic library on the target machine where the application will run (yocto.dll for Windows, libyocto.so.1.0.1 for Mac OS X and Linux).

To integrate the dynamic Yoctopuce library to your project, you must include the Sources directory of the Yoctopuce library into your IncludePath, and add the sub-directory Binaries/... corresponding to your operating system into your LibPath.

Then, for you project to build correctly, you need to link with your project the dynamic Yoctopuce library and the prerequisite system libraries:

• For Windows: yocto.lib
• For Mac OS X: libyocto, IOKit.framework, and CoreFoundation.framework
• For Linux: libyocto, libm, libpthread, libusb1.0, and libstdc++.

With GCC, the command line to compile is simply:

gcc (...) -lyocto -lm -lpthread -lusb-1.0 -lstdc++

10. Using Yocto-MaxiCoupler with Objective-C

Objective-C is language of choice for programming on Mac OS X, due to its integration with the Cocoa framework. In order to use the Objective-C library, you need XCode version 4.2 (earlier versions will not work), available freely when you run Lion. If you are still under Snow Leopard, you need to be registered as Apple developer to be able to download XCode 4.2. The Yoctopuce library is ARC compatible. You can therefore implement your projects either using the traditional retain / release method, or using the Automatic Reference Counting.

Yoctopuce Objective-C libraries²⁶ are integrally provided as source files. A section of the low-level library is written in pure C, but you should not need to interact directly with it: everything was done to ensure the simplest possible interaction from Objective-C.

You will soon notice that the Objective-C API defines many functions which return objects. You do not need to deallocate these objects yourself, the API does it automatically at the end of the application.

In order to keep them simple, all the examples provided in this documentation are console applications. Naturally, the libraries function in a strictly identical manner if you integrate them in an application with a graphical interface. You can find on Yoctopuce blog a detailed example²⁷ with video shots showing how to integrate the library into your projects.

10.1. Control of the Relay function

Launch Xcode 4.2 and open the corresponding sample project provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

There are only a few really important lines in this example. We will look at them in details.

yocto_api.h et yocto_relay.h

These two import files provide access to the functions allowing you to manage Yoctopuce modules. yocto_api.h must always be used, yocto_relay.h is necessary to manage modules containing a relay, such as Yocto-MaxiCoupler.

[YAPI RegisterHub]

The [YAPI RegisterHub] function initializes the Yoctopuce API and indicates where the modules should be looked for. When used with the parameter @"usb", it will use the modules locally connected to the computer running the library. If the initialization does not succeed, this function returns a value different from YAPI_SUCCESS and errmsg contains the error message.

[Relay FindRelay]

The [Relay FindRelay] function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

[Relay FindRelay] returns an object which you can then use at will to control the relay.

isOnline

The isOnline method of the object returned by [Relay FindRelay] allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

10.2. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type get_xxxx, and properties which are not read-only can be modified with the help of the set_xxx: method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding set_xxx: function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the saveToFlash method. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not NULL. Below a short example listing the connected modules.

10.3. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

11. Using Yocto-MaxiCoupler with Visual Basic .NET

VisualBasic has long been the most favored entrance path to the Microsoft world. Therefore, we had to provide our library for this language, even if the new trend is shifting to C#. All the examples and the project models are tested with Microsoft VisualBasic 2010 Express, freely available on the Microsoft web site²⁸.

11.1. Installation

Download the Visual Basic Yoctopuce library from the Yoctopuce web site²⁹. There is no setup program, simply copy the content of the zip file into the directory of your choice. You mostly need the content of the Sources directory. The other directories contain the documentation and a few sample programs. All sample projects are Visual Basic 2010, projects, if you are using a previous version, you may have to recreate the projects structure from scratch.

11.2. Using the Yoctopuce API in a Visual Basic project

The Visual Basic.NET Yoctopuce library is composed of a DLL and of source files in Visual Basic. The DLL is not a .NET DLL, but a classic DLL, written in C, which manages the low level communications with the modules³⁰. The source files in Visual Basic manage the high level part of the API. Therefore, your need both this DLL and the .vb files of the sources directory to create a project managing Yoctopuce modules.

Configuring a Visual Basic project

The following indications are provided for Visual Studio Express 2010, but the process is similar for other versions. Start by creating your project. Then, on the Solution Explorer panel, right click on your project, and select "Add" and then "Add an existing item".

A file selection window opens. Select the yocto_api.vb file and the files corresponding to the functions of the Yoctopuce modules that your project is going to manage. If in doubt, select all the files.

You then have the choice between simply adding these files to your project, or to add them as links (the Add button is in fact a scroll-down menu). In the first case, Visual Studio copies the selected files into your project. In the second case, Visual Studio simply keeps a link on the original files. We recommend you to use links, which makes updates of the library much easier.

Then add in the same manner the yapi.dll DLL, located in the Sources/dll directory³¹. Then, from the Solution Explorer window, right click on the DLL, select Properties and in the Properties panel, set the Copy to output folder to always. You are now ready to use your Yoctopuce modules from Visual Studio.

In order to keep them simple, all the examples provided in this documentation are console applications. Naturally, the libraries function in a strictly identical manner if you integrate them in an application with a graphical interface.

11.3. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a Visual Basic code snipplet to use the Relay function.

Let's look at these lines in more details.

yRegisterHub

The yRegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. When used with the parameter "usb", it will use the modules locally connected to the computer running the library. If the initialization does not succeed, this function returns a value different from YAPI_SUCCESS and errmsg contains the error message.

yFindRelay

The yFindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

yFindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by yFindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by yFindRelay switches the relay position to one of its two outputs. The two possible parameter values are Y_STATE_A for output A, and Y_STATE_B for output B.

A real example

Launch Microsoft VisualBasic and open the corresponding sample project provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

In this example, you will recognize the functions explained above, but this time used with all side materials needed to make it work nicely as a small demo.

11.4. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type get_xxxx(), and properties which are not read-only can be modified with the help of the set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not Nothing. Below a short example listing the connected modules.

11.5. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

12. Using Yocto-MaxiCoupler with C#

C# (pronounced C-Sharp) is an object-oriented programming language promoted by Microsoft, it is somewhat similar to Java. Like Visual-Basic and Delphi, it allows you to create Windows applications quite easily. All the examples and the project models are tested with Microsoft C# 2010 Express, freely available on the Microsoft web site³².

Our programming library is also compatible with Mono, the open source version of C# that also works on Linux and MacOS. You will find on our web site various articles that describe how to configure Mono to use our library.

12.1. Installation

Download the Visual C# Yoctopuce library from the Yoctopuce web site³³. There is no setup program, simply copy the content of the zip file into the directory of your choice. You mostly need the content of the Sources directory. The other directories contain the documentation and a few sample programs. All sample projects are Visual C# 2010, projects, if you are using a previous version, you may have to recreate the projects structure from scratch.

12.2. Using the Yoctopuce API in a Visual C# project

The Visual C#.NET Yoctopuce library is composed of a DLL and of source files in Visual C#. The DLL is not a .NET DLL, but a classic DLL, written in C, which manages the low level communications with the modules³⁴. The source files in Visual C# manage the high level part of the API. Therefore, your need both this DLL and the .cs files of the sources directory to create a project managing Yoctopuce modules.

Configuring a Visual C# project

The following indications are provided for Visual Studio Express 2010, but the process is similar for other versions. Start by creating your project. Then, on the Solution Explorer panel, right click on your project, and select "Add" and then "Add an existing item".

A file selection window opens. Select the yocto_api.cs file and the files corresponding to the functions of the Yoctopuce modules that your project is going to manage. If in doubt, select all the files.

You then have the choice between simply adding these files to your project, or to add them as links (the Add button is in fact a scroll-down menu). In the first case, Visual Studio copies the selected files into your project. In the second case, Visual Studio simply keeps a link on the original files. We recommend you to use links, which makes updates of the library much easier.

Then add in the same manner the yapi.dll DLL, located in the Sources/dll directory³⁵. Then, from the Solution Explorer window, right click on the DLL, select Properties and in the Properties panel, set the Copy to output folder to always. You are now ready to use your Yoctopuce modules from Visual Studio.

In order to keep them simple, all the examples provided in this documentation are console applications. Naturally, the libraries function in a strictly identical manner if you integrate them in an application with a graphical interface.

12.3. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a C# code snipplet to use the Relay function.

Let's look at these lines in more details.

YAPI.RegisterHub

The YAPI.RegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. When used with the parameter "usb", it will use the modules locally connected to the computer running the library. If the initialization does not succeed, this function returns a value different from YAPI.SUCCESS and errmsg contains the error message.

YRelay.FindRelay

The YRelay.FindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

YRelay.FindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by YRelay.FindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

A real example

Launch Microsoft Visual C# and open the corresponding sample project provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

In this example, you will recognize the functions explained above, but this time used with all side materials needed to make it work nicely as a small demo.

12.4. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type YModule.get_xxxx(), and properties which are not read-only can be modified with the help of the YModule.set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding YModule.set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the YModule.saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the YModule.revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the YModule.saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the YModule.yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not null. Below a short example listing the connected modules.

12.5. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

13. Using the Yocto-MaxiCoupler with Universal Windows Platform

Universal Windows Platform (UWP) is not a language per say, but a software platform created by Microsoft. This platform allows you to run a new type of applications: the universal Windows applications. These applications can work on all machines running under Windows 10. This includes computers, tablets, smart phones, XBox One, and also Windows IoT Core.

The Yoctopuce UWP library allows you to use Yoctopuce modules in a universal Windows application and is written in C# in its entirety. You can add it to a Visual Studio 2017³⁶ project.

13.1. Blocking and asynchronous functions

The Universal Windows Platform does not use the Win32 API but only the Windows Runtime API which is available on all the versions of Windows 10 and for any architecture. Thanks to this library, you can use UWP on all the Windows 10 versions, including Windows 10 IoT Core.

However, using the new UWP API has some consequences: the Windows Runtime API to access the USB ports is asynchronous, and therefore the Yoctopuce library must be asynchronous as well. Concretely, the asynchronous methods do not return a result directly but a Task or Task<> object and the result can be obtained later. Fortunately, the C# language, version 6, supports the async and await keywords, which simplifies using these functions enormously. You can thus use asynchronous functions in the same way as traditional functions as long as you respect the following two rules:

• The method is declared as asynchronous with the async keyword
• The await keyword is added when calling an asynchronous function

Example: Our library follows these two rules and can therefore use the await notation.

For you not to have to wonder wether a function is asynchronous or not, there is the following convention: all the public methods of the UWP library are asynchronous, that is that you must call them with the await keyword, except:

• GetTickCount(), because measuring time in an asynchronous manner does not make a lot of sense...
• FindModule(), FirstModule(), nextModule(), ... because detecting and enumerating modules is performed as a background task on internal structures which are managed transparently. It is therefore not necessary to use blocking functions while going though the lists of modules.

13.2. Installation

Download the Yoctopuce library for $LANG$ from the Yoctopuce web site³⁷. There is no installation software, simply copy the content of the zip file in a directory of your choice. You essentially need the content of the Sources directory. The other directories contain documentation and a few sample programs. Sample projects are Visual Studio 2017 projects. Visual Studio 2017 is available on the Microsoft web site³⁸.

13.3. Using the Yoctopuce API in a Visual Studio project

Start by creating your project. Then, from the Solution Explorer panel right click on your project and select Add then Existing element .

A file chooser opens: select all the files in the library Sources directory.

You then have the choice between simply adding the files to your project or adding them as a link (the Add button is actually a drop-down menu). In the first case, Visual Studio copies the selected files into your project. In the second case, Visual Studio simply creates a link to the original files. We recommend to use links, as a potential library update is thus much easier.

The Package.appxmanifest file

By default a Universal Windows application doesn't have access rights to the USB ports. If you want to access USB devices, you must imperatively declare it in the Package.appxmanifest file.

Unfortunately, the edition window of this file doesn't allow this operation and you must modify the Package.appxmanifest file by hand. In the "Solution Explorer" panel, right click on the Package.appxmanifest and select "View Code".

In this XML file, we must add a DeviceCapability node in the Capabilities node. This node must have a "Name" attribute with a "humaninterfacedevice" value.

Inside this node, you must declare all the modules that can be used. Concretely, for each module, you must add a "Device" node with an "Id" attribute, which has for value a character string "vidpid:USB_VENDORID USB_DEVICE_ID". The Yoctopuce USB_VENDORID is 24e0 and you can find the USB_DEVICE_ID of each Yoctopuce device in the documentation in the "Characteristics" section. Finally, the "Device" node must contain a "Function" node with the "Type" attribute with a value of "usage:ff00 0001".

For the Yocto-MaxiCoupler, here is what you must add in the "Capabilities" node:

Unfortunately, it's not possible to write a rule authorizing all Yoctopuce modules. Therefore, you must imperatively add each module that you want to use.

13.4. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a C# code snippet to use the Relay function.

Let us look at these lines in more details.

YAPI.RegisterHub

The YAPI.RegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. The parameter is the address of the virtual hub able to see the devices. If the string "usb" is passed as parameter, the API works with modules locally connected to the machine. If the initialization does not succeed, an exception is thrown.

YRelay.FindRelay

The YRelay.FindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

YRelay.FindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by YRelay.FindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

13.5. A real example

Launch Visual Studio and open the corresponding project provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

Visual Studio projects contain numerous files, and most of them are not linked to the use of the Yoctopuce library. To simplify reading the code, we regrouped all the code that uses the library in the Demo class, located in the demo.cs file. Properties of this class correspond to the different fields displayed on the screen, and the Run() method contains the code which is run when the "Start" button is pushed.

In this example, you can recognize the functions explained above, but this time used with all the side materials needed to make it work nicely as a small demo.

13.6. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type YModule.get_xxxx(), and properties which are not read-only can be modified with the help of the YModule.set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding YModule.set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the YModule.saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the YModule.revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the YModule.saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the YModule.yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not null. Below a short example listing the connected modules.

13.7. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software.

In the Universal Windows Platform library, error handling is implemented with exceptions. You must therefore intercept and correctly handle these exceptions if you want to have a reliable project which does not crash as soon as you disconnect a module.

Library thrown exceptions are always of the YAPI_Exception type, so you can easily separate them from other exceptions in a try{...} catch{...} block.

Example:

14. Using Yocto-MaxiCoupler with Delphi

Delphi is a descendent of Turbo-Pascal. Originally, Delphi was produced by Borland, Embarcadero now edits it. The strength of this language resides in its ease of use, as anyone with some notions of the Pascal language can develop a Windows application in next to no time. Its only disadvantage is to cost something³⁹.

Delphi libraries are provided not as VCL components, but directly as source files. These files are compatible with most Delphi versions. ⁴⁰

To keep them simple, all the examples provided in this documentation are console applications. Obviously, the libraries work in a strictly identical way with VCL applications.

You will soon notice that the Delphi API defines many functions which return objects. You do not need to deallocate these objects yourself, the API does it automatically at the end of the application.

14.1. Preparation

Go to the Yoctopuce web site and download the Yoctopuce Delphi libraries⁴¹. Uncompress everything in a directory of your choice, add the subdirectory sources in the list of directories of Delphi libraries.⁴²

By default, the Yoctopuce Delphi library uses the yapi.dll DLL, all the applications you will create with Delphi must have access to this DLL. The simplest way to ensure this is to make sure yapi.dll is located in the same directory as the executable file of your application.

14.2. Control of the Relay function

Launch your Delphi environment, copy the yapi.dll DLL in a directory, create a new console application in the same directory, and copy-paste the piece of code below:

There are only a few really important lines in this sample example. We will look at them in details.

yocto_api and yocto_relay

These two units provide access to the functions allowing you to manage Yoctopuce modules. yocto_api must always be used, yocto_relay is necessary to manage modules containing a relay, such as Yocto-MaxiCoupler.

yRegisterHub

The yRegisterHub function initializes the Yoctopuce API and specifies where the modules should be looked for. When used with the parameter 'usb', it will use the modules locally connected to the computer running the library. If the initialization does not succeed, this function returns a value different from YAPI_SUCCESS and errmsg contains the error message.

yFindRelay

The yFindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can also use logical names, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

yFindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by yFindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by yFindRelay switches the relay position to one of its two outputs. The two possible parameter values are Y_STATE_A for output A, and Y_STATE_B for output B.

14.3. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type get_xxxx(), and properties which are not read-only can be modified with the help of the set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not nil. Below a short example listing the connected modules.

14.4. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

15. Using the Yocto-MaxiCoupler with Python

Python is an interpreted object oriented language developed by Guido van Rossum. Among its advantages is the fact that it is free, and the fact that it is available for most platforms, Windows as well as UNIX. It is an ideal language to write small scripts on a napkin. The Yoctopuce library is compatible with Python 2.6+ and 3+. It works under Windows, Mac OS X, and Linux, Intel as well as ARM. The library was tested with Python 2.6 and Python 3.2. Python interpreters are available on the Python web site⁴³.

15.1. Source files

The Yoctopuce library classes⁴⁴ for Python that you will use are provided as source files. Copy all the content of the Sources directory in the directory of your choice and add this directory to the PYTHONPATH environment variable. If you use an IDE to program in Python, refer to its documentation to configure it so that it automatically finds the API source files.

15.2. Dynamic library

A section of the low-level library is written in C, but you should not need to interact directly with it: it is provided as a DLL under Windows, as a .so files under UNIX, and as a .dylib file under Mac OS X. Everything was done to ensure the simplest possible interaction from Python: the distinct versions of the dynamic library corresponding to the distinct operating systems and architectures are stored in the cdll directory. The API automatically loads the correct file during its initialization. You should not have to worry about it.

If you ever need to recompile the dynamic library, its complete source code is located in the Yoctopuce C++ library.

In order to keep them simple, all the examples provided in this documentation are console applications. Naturally, the libraries function in a strictly identical manner if you integrate them in an application with a graphical interface.

15.3. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a Python code snipplet to use the Relay function.

Let's look at these lines in more details.

YAPI.RegisterHub

The yAPI.RegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. When used with the parameter "usb", it will use the modules locally connected to the computer running the library. If the initialization does not succeed, this function returns a value different from YAPI.SUCCESS and errmsg contains the error message.

YRelay.FindRelay

The YRelay.FindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

YRelay.FindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by YRelay.FindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

A real example

Launch Python and open the corresponding sample script provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

In this example, you will recognize the functions explained above, but this time used with all side materials needed to make it work nicely as a small demo.

15.4. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type YModule.get_xxxx(), and properties which are not read-only can be modified with the help of the YModule.set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding YModule.set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the YModule.saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the YModule.revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the YModule.saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the YModule.yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not null. Below a short example listing the connected modules.

15.5. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software. The only way to prevent this is to implement one of the two error handling techniques described below.

The method recommended by most programming languages for unpredictable error handling is the use of exceptions. By default, it is the behavior of the Yoctopuce library. If an error happens while you try to access a module, the library throws an exception. In this case, there are three possibilities:

• If your code catches the exception and handles it, everything goes well.
• If your program is running in debug mode, you can relatively easily determine where the problem happened and view the explanatory message linked to the exception.
• Otherwise... the exception makes your program crash, bang!

As this latest situation is not the most desirable, the Yoctopuce library offers another possibility for error handling, allowing you to create a robust program without needing to catch exceptions at every line of code. You simply need to call the YAPI.DisableExceptions() function to commute the library to a mode where exceptions for all the functions are systematically replaced by specific return values, which can be tested by the caller when necessary. For each function, the name of each return value in case of error is systematically documented in the library reference. The name always follows the same logic: a get_state() method returns a Y_STATE_INVALID value, a get_currentValue method returns a Y_CURRENTVALUE_INVALID value, and so on. In any case, the returned value is of the expected type and is not a null pointer which would risk crashing your program. At worst, if you display the value without testing it, it will be outside the expected bounds for the returned value. In the case of functions which do not normally return information, the return value is YAPI_SUCCESS if everything went well, and a different error code in case of failure.

When you work without exceptions, you can obtain an error code and an error message explaining the source of the error. You can request them from the object which returned the error, calling the errType() and errMessage() methods. Their returned values contain the same information as in the exceptions when they are active.

16. Using the Yocto-MaxiCoupler with Java

Java is an object oriented language created by Sun Microsystem. Beside being free, its main strength is its portability. Unfortunately, this portability has an excruciating price. In Java, hardware abstraction is so high that it is almost impossible to work directly with the hardware. Therefore, the Yoctopuce API does not support native mode in regular Java. The Java API needs a Virtual Hub to communicate with Yoctopuce devices.

16.1. Getting ready

Go to the Yoctopuce web site and download the following items:

• The Java programming library⁴⁵
• The VirtualHub software⁴⁶ for Windows, Mac OS X or Linux, depending on your OS

The library is available as source files as well as a jar file. Decompress the library files in a folder of your choice, connect your modules, run the VirtualHub software, and you are ready to start your first tests. You do not need to install any driver.

In order to keep them simple, all the examples provided in this documentation are console applications. Naturally, the libraries function in a strictly identical manner if you integrate them in an application with a graphical interface.

16.2. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a Java code snippet to use the Relay function.

Let us look at these lines in more details.

YAPI.RegisterHub

The yAPI.RegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. The parameter is the address of the Virtual Hub able to see the devices. If the initialization does not succeed, an exception is thrown.

YRelay.FindRelay

The YRelay.FindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

YRelay.FindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by YRelay.FindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

A real example

Launch you Java environment and open the corresponding sample project provided in the directory Examples/Doc-GettingStarted-Yocto-MaxiCoupler of the Yoctopuce library.

In this example, you will recognize the functions explained above, but this time used with all the side materials needed to make it work nicely as a small demo.

16.3. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type YModule.get_xxxx(), and properties which are not read-only can be modified with the help of the YModule.set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding YModule.set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the YModule.saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the YModule.revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the YModule.saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the YModule.yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not null. Below a short example listing the connected modules.

16.4. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software.

In the Java API, error handling is implemented with exceptions. Therefore you must catch and handle correctly all exceptions that might be thrown by the API if you do not want your software to crash as soon as you unplug a device.

17. Using the Yocto-MaxiCoupler with Android

To tell the truth, Android is not a programming language, it is an operating system developed by Google for mobile appliances such as smart phones and tablets. But it so happens that under Android everything is programmed with the same programming language: Java. Nevertheless, the programming paradigms and the possibilities to access the hardware are slightly different from classical Java, and this justifies a separate chapter on Android programming.

17.1. Native access and VirtualHub

In the opposite to the classical Java API, the Java for Android API can access USB modules natively. However, as there is no VirtualHub running under Android, it is not possible to remotely control Yoctopuce modules connected to a machine under Android. Naturally, the Java for Android API remains perfectly able to connect itself to a VirtualHub running on another OS.

17.2. Getting ready

Go to the Yoctopuce web site and download the Java for Android programming library⁴⁷. The library is available as source files, and also as a jar file. Connect your modules, decompress the library files in the directory of your choice, and configure your Android programming environment so that it can find them.

To keep them simple, all the examples provided in this documentation are snippets of Android applications. You must integrate them in your own Android applications to make them work. However, your can find complete applications in the examples provided with the Java for Android library.

17.3. Compatibility

In an ideal world, you would only need to have a smart phone running under Android to be able to make Yoctopuce modules work. Unfortunately, it is not quite so in the real world. A machine running under Android must fulfil to a few requirements to be able to manage Yoctopuce USB modules natively.

Android 4.x

Android 4.0 (api 14) and following are officially supported. Theoretically, support of USB host functions since Android 3.1. But be aware that the Yoctopuce Java for Android API is regularly tested only from Android 4 onwards.

USB host support

Naturally, not only must your machine have a USB port, this port must also be able to run in host mode. In host mode, the machine literally takes control of the devices which are connected to it. The USB ports of a desktop computer, for example, work in host mode. The opposite of the host mode is the device mode. USB keys, for instance, work in device mode: they must be controlled by a host. Some USB ports are able to work in both modes, they are OTG (On The Go) ports. It so happens that many mobile devices can only work in device mode: they are designed to be connected to a charger or a desktop computer, and nothing else. It is therefore highly recommended to pay careful attention to the technical specifications of a product working under Android before hoping to make Yoctopuce modules work with it.

Unfortunately, having a correct version of Android and USB ports working in host mode is not enough to guaranty that Yoctopuce modules will work well under Android. Indeed, some manufacturers configure their Android image so that devices other than keyboard and mass storage are ignored, and this configuration is hard to detect. As things currently stand, the best way to know if a given Android machine works with Yoctopuce modules consists in trying.

Supported hardware

The library is tested and validated on the following machines:

• Samsung Galaxy S3
• Samsung Galaxy Note 2
• Google Nexus 5
• Google Nexus 7
• Acer Iconia Tab A200
• Asus Tranformer Pad TF300T
• Kurio 7

If your Android machine is not able to control Yoctopuce modules natively, you still have the possibility to remotely control modules driven by a VirtualHub on another OS, or a YoctoHub ⁴⁸.

17.4. Activating the USB port under Android

By default, Android does not allow an application to access the devices connected to the USB port. To enable your application to interact with a Yoctopuce module directly connected on your tablet on a USB port, a few additional steps are required. If you intend to interact only with modules connected on another machine through the network, you can ignore this section.

In your AndroidManifest.xml, you must declare using the "USB Host" functionality by adding the <uses-feature android:name="android.hardware.usb.host" /> tag in the manifest section.

When first accessing a Yoctopuce module, Android opens a window to inform the user that the application is going to access the connected module. The user can deny or authorize access to the device. If the user authorizes the access, the application can access the connected device as long as it stays connected. To enable the Yoctopuce library to correctly manage these authorizations, your must provide a pointer on the application context by calling the EnableUSBHost method of the YAPI class before the first USB access. This function takes as arguments an object of the android.content.Context class (or of a subclass). As the Activity class is a subclass of Context, it is simpler to call YAPI.EnableUSBHost(this); in the method onCreate of your application. If the object passed as parameter is not of the correct type, a YAPI_Exception exception is generated.

Autorun

It is possible to register your application as a default application for a USB module. In this case, as soon as a module is connected to the system, the application is automatically launched. You must add <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"/> in the section <intent-filter> of the main activity. The section <activity> must have a pointer to an XML file containing the list of USB modules which can run the application.

The XML file containing the list of modules allowed to run the application must be saved in the res/xml directory. This file contains a list of USB vendorId and deviceID in decimal. The following example runs the application as soon as a Yocto-Relay or a YoctoPowerRelay is connected. You can find the vendorID and the deviceID of Yoctopuce modules in the characteristics section of the documentation.

17.5. Control of the Relay function

A few lines of code are enough to use a Yocto-MaxiCoupler. Here is the skeleton of a Java code snippet to use the Relay function.

Let us look at these lines in more details.

YAPI.EnableUSBHost

The YAPI.EnableUSBHost function initializes the API with the Context of the current application. This function takes as argument an object of the android.content.Context class (or of a subclass). If you intend to connect your application only to other machines through the network, this function is facultative.

YAPI.RegisterHub

The yAPI.RegisterHub function initializes the Yoctopuce API and indicates where the modules should be looked for. The parameter is the address of the virtual hub able to see the devices. If the string "usb" is passed as parameter, the API works with modules locally connected to the machine. If the initialization does not succeed, an exception is thrown.

YRelay.FindRelay

The YRelay.FindRelay function allows you to find a relay from the serial number of the module on which it resides and from its function name. You can use logical names as well, as long as you have initialized them. Let us imagine a Yocto-MaxiCoupler module with serial number YMXCOUPL-123456 which you have named "MyModule", and for which you have given the relay1 function the name "MyFunction". The following five calls are strictly equivalent, as long as "MyFunction" is defined only once.

YRelay.FindRelay returns an object which you can then use at will to control the relay.

isOnline

The isOnline() method of the object returned by YRelay.FindRelay allows you to know if the corresponding module is present and in working order.

set_state

The set_state() method of the objet returned by YRelay.FindRelay switches the relay position to one of its two outputs. The two possible parameter values are YRelay.STATE_A for output A, and YRelay.STATE_B for output B.

A real example

Launch you Java environment and open the corresponding sample project provided in the directory Examples//Doc-Examples of the Yoctopuce library.

In this example, you can recognize the functions explained above, but this time used with all the side materials needed to make it work nicely as a small demo.

17.6. Control of the module part

Each module can be controlled in a similar manner, you can find below a simple sample program displaying the main parameters of the module and enabling you to activate the localization beacon.

Each property xxx of the module can be read thanks to a method of type YModule.get_xxxx(), and properties which are not read-only can be modified with the help of the YModule.set_xxx() method. For more details regarding the used functions, refer to the API chapters.

Changing the module settings

When you want to modify the settings of a module, you only need to call the corresponding YModule.set_xxx() function. However, this modification is performed only in the random access memory (RAM) of the module: if the module is restarted, the modifications are lost. To memorize them persistently, it is necessary to ask the module to save its current configuration in its permanent memory. To do so, use the YModule.saveToFlash() method. Inversely, it is possible to force the module to forget its current settings by using the YModule.revertFromFlash() method. The short example below allows you to modify the logical name of a module.

Warning: the number of write cycles of the nonvolatile memory of the module is limited. When this limit is reached, nothing guaranties that the saving process is performed correctly. This limit, linked to the technology employed by the module micro-processor, is located at about 100000 cycles. In short, you can use the YModule.saveToFlash() function only 100000 times in the life of the module. Make sure you do not call this function within a loop.

Listing the modules

Obtaining the list of the connected modules is performed with the YModule.yFirstModule() function which returns the first module found. Then, you only need to call the nextModule() function of this object to find the following modules, and this as long as the returned value is not null. Below a short example listing the connected modules.

17.7. Error handling

When you implement a program which must interact with USB modules, you cannot disregard error handling. Inevitably, there will be a time when a user will have unplugged the device, either before running the software, or even while the software is running. The Yoctopuce library is designed to help you support this kind of behavior, but your code must nevertheless be conceived to interpret in the best possible way the errors indicated by the library.

The simplest way to work around the problem is the one used in the short examples provided in this chapter: before accessing a module, check that it is online with the isOnline function, and then hope that it will stay so during the fraction of a second necessary for the following code lines to run. This method is not perfect, but it can be sufficient in some cases. You must however be aware that you cannot completely exclude an error which would occur after the call to isOnline and which could crash the software.

In the Java API for Android, error handling is implemented with exceptions. Therefore you must catch and handle correctly all exceptions that might be thrown by the API if you do not want your software to crash soon as you unplug a device.

18. Advanced programming

The preceding chapters have introduced, in each available language, the basic programming functions which can be used with your Yocto-MaxiCoupler module. This chapter presents in a more generic manner a more advanced use of your module. Examples are provided in the language which is the most popular among Yoctopuce customers, that is C#. Nevertheless, you can find complete examples illustrating the concepts presented here in the programming libraries of each language.

To remain as concise as possible, examples provided in this chapter do not perform any error handling. Do not copy them "as is" in a production application.

18.1. Event programming

The methods to manage Yoctopuce modules which we presented to you in preceding chapters were polling functions, consisting in permanently asking the API if something had changed. While easy to understand, this programming technique is not the most efficient, nor the most reactive. Therefore, the Yoctopuce programming API also provides an event programming model. This technique consists in asking the API to signal by itself the important changes as soon as they are detected. Each time a key parameter is modified, the API calls a callback function which you have defined in advance.

Detecting module arrival and departure

Hot-plug management is important when you work with USB modules because, sooner or later, you will have to connect or disconnect a module when your application is running. The API is designed to manage module unexpected arrival or departure in a transparent way. But your application must take this into account if it wants to avoid pretending to use a disconnected module.

Event programming is particularly useful to detect module connection/disconnection. Indeed, it is simpler to be told of new connections rather than to have to permanently list the connected modules to deduce which ones just arrived and which ones left. To be warned as soon as a module is connected, you need three pieces of code.

The callback

The callback is the function which is called each time a new Yoctopuce module is connected. It takes as parameter the relevant module.

Initialization

You must then tell the API that it must call the callback when a new module is connected.

Note that if modules are already connected when the callback is registered, the callback is called for each of the already connected modules.

Triggering callbacks

A classis issue of callback programming is that these callbacks can be triggered at any time, including at times when the main program is not ready to receive them. This can have undesired side effects, such as dead-locks and other race conditions. Therefore, in the Yoctopuce API, module arrival/departure callbacks are called only when the UpdateDeviceList() function is running. You only need to call UpdateDeviceList() at regular intervals from a timer or from a specific thread to precisely control when the calls to these callbacks happen:

In a similar way, it is possible to have a callback when a module is disconnected. You can find a complete example implemented in your favorite programming language in the Examples/Prog-EventBased directory of the corresponding library.

Be aware that in most programming languages, callbacks must be global procedures, and not methods. If you wish for the callback to call the method of an object, define your callback as a global procedure which then calls your method.

19. Firmware Update

There are multiples way to update the firmware of a Yoctopuce module..

19.1. The VirtualHub or the YoctoHub

It is possible to update the firmware directly from the web interface of the VirtualHub or the YoctoHub. The configuration panel of the module has an "upgrade" button to start a wizard that will guide you through the firmware update procedure.

In case the firmware update fails for any reason, and the module does no start anymore, simply unplug the module then plug it back while maintaining the Yocto-button down. The module will boot in "firmware update" mode and will appear in the VirtualHub interface below the module list.

19.2. The command line library

All the command line tools can update Yoctopuce modules thanks to the downloadAndUpdate command. The module selection mechanism works like for a traditional command. The [target] is the name of the module that you want to update. You can also use the "any" or "all" aliases, or even a name list, where the names are separated by commas, without spaces.

The following example updates all the Yoctopuce modules connected by USB.

19.3. The Android application Yocto-Firmware

You can update your module firmware from your Android phone or tablet with the Yocto-Firmware application. This application lists all the Yoctopuce modules connected by USB and checks if a more recent firmware is available on www.yoctopuce.com. If a more recent firmware is available, you can update the module. The application is responsible for downloading and installing the new firmware while preserving the module parameters.

Please note: while the firmware is being updated, the module restarts several times. Android interprets a USB device reboot as a disconnection and reconnection of the USB device and asks the authorization to use the USB port again. The user must click on OK for the update process to end successfully.

19.4. Updating the firmware with the programming library

If you need to integrate firmware updates in your application, the libraries offer you an API to update your modules. ⁴⁹

Saving and restoring parameters

The get_allSettings() method returns a binary buffer enabling you to save a module persistent parameters. This function is very useful to save the network configuration of a YoctoHub for example.

You can then apply these parameters to other modules with the set_allSettings() method.

Finding the correct firmware

The first step to update a Yoctopuce module is to find which firmware you must use. The checkFirmware(path, onlynew) method of the YModule object does exactly this. The method checks that the firmware given as argument (path) is compatible with the module. If the onlynew parameter is set, this method checks that the firmware is more recent than the version currently used by the module. When the file is not compatible (or if the file is older than the installed version), this method returns an empty string. In the opposite, if the file is valid, the method returns a file access path.

The following piece of code checks that the c:\tmp\METEOMK1.17328.byn is compatible with the module stored in the m variable .

The argument can be a directory (instead of a file). In this case, the method checks all the files of the directory recursively and returns the most recent compatible firmware. The following piece of code checks whether there is a more recent firmware in the c:\tmp\ directory.

You can also give the "www.yoctopuce.com" string as argument to check whether there is a more recent published firmware on Yoctopuce's web site. In this case, the method returns the firmware URL. You can use this URL to download the firmware on your disk or use this URL when updating the firmware (see below). Obviously, this possibility works only if your machine is connected to Internet.

Updating the firmware

A firmware update can take several minutes. That is why the update process is run as a background task and is driven by the user code thanks to the YFirmwareUdpate class.

To update a Yoctopuce module, you must obtain an instance of the YFirmwareUdpate class with the updateFirmware method of a YModule object. The only parameter of this method is the path of the firmware that you want to install. This method does not immediately start the update, but returns a YFirmwareUdpate object configured to update the module.

The startUpdate() method starts the update as a background task. This background task automatically takes care of

1. saving the module parameters
2. restarting the module in "update" mode
3. updating the firmware
4. starting the module with the new firmware version
5. restoring the parameters

The get_progress() and get_progressMessage() methods enable you to follow the progression of the update. get_progress() returns the progression as a percentage (100 = update complete). get_progressMessage() returns a character string describing the current operation (deleting, writing, rebooting, ...). If the get_progress method returns a negative value, the update process failed. In this case, the get_progressMessage() returns an error message.

The following piece of code starts the update and displays the progress on the standard output.

An Android characteristic

You can update a module firmware using the Android library. However, for modules connected by USB, Android asks the user to authorize the application to access the USB port.

During firmware update, the module restarts several times. Android interprets a USB device reboot as a disconnection and a reconnection to the USB port, and prevents all USB access as long as the user has not closed the pop-up window. The use has to click on OK for the update process to continue correctly. You cannot update a module connected by USB to an Android device without having the user interacting with the device.

19.5. The "update" mode

If you want to erase all the parameters of a module or if your module does not start correctly anymore, you can install a firmware from the "update" mode.

To force the module to work in "update" mode, disconnect it, wait a few seconds, and reconnect it while maintaining the Yocto-button down. This will restart the module in "update" mode. This update mode is protected against corruptions and is always available.

In this mode, the module is not detected by the YModule objects anymore. To obtain the list of connected modules in "update" mode, you must use the YAPI.GetAllBootLoaders() function. This function returns a character string array with the serial numbers of the modules in "update" mode.

The update process is identical to the standard case (see the preceding section), but you must manually instantiate the YFirmwareUpdate object instead of calling module.updateFirmware(). The constructor takes as argument three parameters: the module serial number, the path of the firmware to be installed, and a byte array with the parameters to be restored at the end of the update (or null to restore default parameters).

20. Using with unsupported languages

Yoctopuce modules can be driven from most common programming languages. New languages are regularly added, depending on the interest expressed by Yoctopuce product users. Nevertheless, some languages are not, and will never be, supported by Yoctopuce. There can be several reasons for this: compilers which are not available anymore, unadapted environments, etc.

However, there are alternative methods to access Yoctopuce modules from an unsupported programming language.

20.1. Command line

The easiest method to drive Yoctopuce modules from an unsupported programming language is to use the command line API through system calls. The command line API is in fact made of a group of small executables which are easy to call. Their output is also easy to analyze. As most programming languages allow you to make system calls, the issue is solved with a few lines of code.

However, if the command line API is the easiest solution, it is neither the fastest nor the most efficient. For each call, the executable must initialize its own API and make an inventory of USB connected modules. This requires about one second per call.

20.2. VirtualHub and HTTP GET

The VirtualHub is available on almost all current platforms. It is generally used as a gateway to provide access to Yoctopuce modules from languages which prevent direct access to hardware layers of a computer (JavaScript, PHP, Java, ...).

In fact, the VirtualHub is a small web server able to route HTTP requests to Yoctopuce modules. This means that if you can make an HTTP request from your programming language, you can drive Yoctopuce modules, even if this language is not officially supported.

REST interface

At a low level, the modules are driven through a REST API. Thus, to control a module, you only need to perform appropriate requests on the VirtualHub. By default, the VirtualHub HTTP port is 4444.

An important advantage of this technique is that preliminary tests are very easy to implement. You only need a VirtualHub and a simple web browser. If you copy the following URL in your preferred browser, while the VirtualHub is running, you obtain the list of the connected modules.

Note that the result is displayed as text, but if you request whitePages.xml, you obtain an XML result. Likewise, whitePages.json allows you to obtain a JSON result. The html extension even allows you to display a rough interface where you can modify values in real time. The whole REST API is available in these different formats.

Driving a module through the REST interface

Each Yoctopuce module has its own REST interface, available in several variants. Let us imagine a Yocto-MaxiCoupler with the YMXCOUPL-12345 serial number and the myModule logical name. The following URL allows you to know the state of the module.

You can naturally also use the module logical name rather than its serial number.

To retrieve the value of a module property, simply add the name of the property below module. For example, if you want to know the signposting led luminosity, send the following request:

To change the value of a property, modify the corresponding attribute. Thus, to modify the luminosity, send the following request:

Driving the module functions through the REST interface

The module functions can be manipulated in the same way. To know the state of the relay function, build the following URL:

Note that if you can use logical names for the modules instead of their serial number, you cannot use logical names for functions. Only hardware names are authorized to access functions.

You can retrieve a module function attribute in a way rather similar to that used with the modules. For example:

Rather logically, attributes can be modified in the same manner.

You can find the list of available attributes for your Yocto-MaxiCoupler at the beginning of the Programming chapter.

Accessing Yoctopuce data logger through the REST interface

This section only applies to devices with a built-in data logger.

The preview of all recorded data streams can be retrieved in JSON format using the following URL:

Individual measures for any given stream can be obtained by appending the desired function identifier as well as start time of the stream:

20.3. Using dynamic libraries

The low level Yoctopuce API is available under several formats of dynamic libraries written in C. The sources are available with the C++ API. If you use one of these low level libraries, you do not need the VirtualHub anymore.

Filename	Platform
libyapi.dylib	Max OS X
libyapi-amd64.so	Linux Intel (64 bits)
libyapi-armel.so	Linux ARM EL
libyapi-armhf.so	Linux ARM HL
libyapi-i386.so	Linux Intel (32 bits)
yapi64.dll	Windows (64 bits)
yapi.dll	Windows (32 bits)

These dynamic libraries contain all the functions necessary to completely rebuild the whole high level API in any language able to integrate these libraries. This chapter nevertheless restrains itself to describing basic use of the modules.

Driving a module

The three essential functions of the low level API are the following:

The yapiInitAPI function initializes the API and must be called once at the beginning of the program. For a USB type connection, the connection_type parameter takes value 1. The errmsg parameter must point to a 255 character buffer to retrieve a potential error message. This pointer can also point to null. The function returns a negative integer in case of error, zero otherwise.

The yapiUpdateDeviceList manages the inventory of connected Yoctopuce modules. It must be called at least once. To manage hot plug and detect potential newly connected modules, this function must be called at regular intervals. The forceupdate parameter must take value 1 to force a hardware scan. The errmsg parameter must point to a 255 character buffer to retrieve a potential error message. This pointer can also point to null. The function returns a negative integer in case of error, zero otherwise.

Finally, the yapiHTTPRequest function sends HTTP requests to the module REST API. The device parameter contains the serial number or the logical name of the module which you want to reach. The request parameter contains the full HTTP request (including terminal line breaks). buffer points to a character buffer long enough to contain the answer. buffsize is the size of the buffer. fullsize is a pointer to an integer to which will be assigned the actual size of the answer. The errmsg parameter must point to a 255 character buffer to retrieve a potential error message. This pointer can also point to null. The function returns a negative integer in case of error, zero otherwise.

The format of the requests is the same as the one described in the VirtualHub et HTTP GET section. All the character strings used by the API are strings made of 8-bit characters: Unicode and UTF8 are not supported.

The resutlt returned in the buffer variable respects the HTTP protocol. It therefore includes an HTTP header. This header ends with two empty lines, that is a sequence of four ASCII characters 13, 10, 13, 10.

Here is a sample program written in pascal using the yapi.dll DLL to read and then update the luminosity of a module.

Module inventory

To perform an inventory of Yoctopuce modules, you need two functions from the dynamic library:

The yapiGetAllDevices function retrieves the list of all connected modules as a list of handles. buffer points to a 32-bit integer array which contains the returned handles. maxsize is the size in bytes of the buffer. To neededsize is assigned the necessary size to store all the handles. From this, you can deduce either the number of connected modules or that the input buffer is too small. The errmsg parameter must point to a 255 character buffer to retrieve a potential error message. This pointer can also point to null. The function returns a negative integer in case of error, zero otherwise.

The yapiGetDeviceInfo function retrieves the information related to a module from its handle. devdesc is a 32-bit integer representing the module and which was obtained through yapiGetAllDevices. infos points to a data structure in which the result is stored. This data structure has the following format:

Name	Type	Size (bytes)	Description
vendorid	int	4	Yoctopuce USB ID
deviceid	int	4	Module USB ID
devrelease	int	4	Module version
nbinbterfaces	int	4	Number of USB interfaces used by the module
manufacturer	char[]	20	Yoctopuce (null terminated)
productname	char[]	28	Model (null terminated)
serial	char[]	20	Serial number (null terminated)
logicalname	char[]	20	Logical name (null terminated)
firmware	char[]	22	Firmware version (null terminated)
beacon	byte	1	Beacon state (0/1)

The errmsg parameter must point to a 255 character buffer to retrieve a potential error message.

Here is a sample program written in pascal using the yapi.dll DLL to list the connected modules.

VB6 and yapi.dll

Each entry point from the yapi.dll is duplicated. You will find one regular C-decl version and one Visual Basic 6 compatible version, prefixed with vb6_.

20.4. Porting the high level library

As all the sources of the Yoctopuce API are fully provided, you can very well port the whole API in the language of your choice. Note, however, that a large portion of the API source code is automatically generated.

Therefore, it is not necessary for you to port the complete API. You only need to port the yocto_api file and one file corresponding to a function, for example yocto_relay. After a little additional work, Yoctopuce is then able to generate all other files. Therefore, we highly recommend that you contact Yoctopuce support before undertaking to port the Yoctopuce library in another language. Collaborative work is advantageous to both parties.

21. High-level API Reference

This chapter summarizes the high-level API functions to drive your Yocto-MaxiCoupler. Syntax and exact type names may vary from one language to another, but, unless otherwise stated, all the functions are available in every language. For detailed information regarding the types of arguments and return values for a given language, refer to the definition file for this language (yocto_api.* as well as the other yocto_* files that define the function interfaces).

For languages which support exceptions, all of these functions throw exceptions in case of error by default, rather than returning the documented error value for each function. This is by design, to facilitate debugging. It is however possible to disable the use of exceptions using the yDisableExceptions() function, in case you prefer to work with functions that return error values.

This chapter does not repeat the programming concepts described earlier, in order to stay as concise as possible. In case of doubt, do not hesitate to go back to the chapter describing in details all configurable attributes.

21.1. General functions

These general functions should be used to initialize and configure the Yoctopuce library. In most cases, a simple call to function yRegisterHub() should be enough. The module-specific functions yFind...() or yFirst...() should then be used to retrieve an object that provides interaction with the module.

Global functions
yCheckLogicalName(name)
Checks if a given string is valid as logical name for a module or a function.
yClearHTTPCallbackCacheDir(bool_removeFiles)
Disables the HTTP callback cache.
yDisableExceptions()
Disables the use of exceptions to report runtime errors.
yEnableExceptions()
Re-enables the use of exceptions for runtime error handling.
yEnableUSBHost(osContext)
This function is used only on Android.
yFreeAPI()
Frees dynamically allocated memory blocks used by the Yoctopuce library.
yGetAPIVersion()
Returns the version identifier for the Yoctopuce library in use.
yGetCacheValidity()
Returns the validity period of the data loaded by the library.
yGetDeviceListValidity()
Returns the time between each forced enumeration of the YoctoHub used.
yGetTickCount()
Returns the current value of a monotone millisecond-based time counter.
yHandleEvents(errmsg)
Maintains the device-to-library communication channel.
yInitAPI(mode, errmsg)
Initializes the Yoctopuce programming library explicitly.
yPreregisterHub(url, errmsg)
Fault-tolerant alternative to RegisterHub().
yRegisterDeviceArrivalCallback(arrivalCallback)
Register a callback function, to be called each time a device is plugged.
yRegisterDeviceRemovalCallback(removalCallback)
Register a callback function, to be called each time a device is unplugged.
yRegisterHub(url, errmsg)
Setup the Yoctopuce library to use modules connected on a given machine.
yRegisterHubDiscoveryCallback(hubDiscoveryCallback)
Register a callback function, to be called each time an Network Hub send an SSDP message.
yRegisterHubWebsocketCallback(ws, errmsg, authpwd)
Variant to RegisterHub() used to initialize Yoctopuce API on an existing Websocket session, as happens for incoming websocket callbacks.
yRegisterLogFunction(logfun)
Registers a log callback function.
ySelectArchitecture(arch)
Select the architecture or the library to be loaded to access to USB.
ySetCacheValidity(cacheValidityMs)
Change the validity period of the data loaded by the library.
ySetDelegate(object)
(Objective-C only) Register an object that must follow the protocol YDeviceHotPlug.
ySetDeviceListValidity(deviceListValidity)
Change the time between each forced enumeration of the YoctoHub used.
ySetHTTPCallbackCacheDir(str_directory)
Enables the HTTP callback cache.
ySetTimeout(callback, ms_timeout, args)
Invoke the specified callback function after a given timeout.
ySetUSBPacketAckMs(pktAckDelay)
Enables the acknowledge of every USB packet received by the Yoctopuce library.
ySleep(ms_duration, errmsg)
Pauses the execution flow for a specified duration.
yTestHub(url, mstimeout, errmsg)
Test if the hub is reachable.
yTriggerHubDiscovery(errmsg)
Force a hub discovery, if a callback as been registered with yRegisterHubDiscoveryCallback it will be called for each net work hub that will respond to the discovery.
yUnregisterHub(url)
Setup the Yoctopuce library to no more use modules connected on a previously registered machine with RegisterHub.
yUpdateDeviceList(errmsg)
Triggers a (re)detection of connected Yoctopuce modules.
yUpdateDeviceList_async(callback, context)
Triggers a (re)detection of connected Yoctopuce modules.

YAPI.CheckLogicalName()
yCheckLogicalName()yCheckLogicalName()yCheckLogicalName()[YAPI CheckLogicalName: ]yCheckLogicalName()yCheckLogicalName()YAPI.CheckLogicalName()YAPI.CheckLogicalName()YAPI.CheckLogicalName()YAPI.CheckLogicalName()yCheckLogicalName()YAPI.CheckLogicalName()

Checks if a given string is valid as logical name for a module or a function.

A valid logical name has a maximum of 19 characters, all among A..Z, a..z, 0..9, _, and -. If you try to configure a logical name with an incorrect string, the invalid characters are ignored.

Parameters :

Returns :

true if the name is valid, false otherwise.

YAPI.ClearHTTPCallbackCacheDir()
yClearHTTPCallbackCacheDir()yClearHTTPCallbackCacheDir()

Disables the HTTP callback cache.

This method disables the HTTP callback cache, and can additionally cleanup the cache directory.

Parameters :

Returns :

nothing.

YAPI.DisableExceptions()
yDisableExceptions()yDisableExceptions()yDisableExceptions()[YAPI DisableExceptions]yDisableExceptions()yDisableExceptions()YAPI.DisableExceptions()YAPI.DisableExceptions()YAPI.DisableExceptions()yDisableExceptions()YAPI.DisableExceptions()

Disables the use of exceptions to report runtime errors.

When exceptions are disabled, every function returns a specific error value which depends on its type and which is documented in this reference manual.

YAPI.EnableExceptions()
yEnableExceptions()yEnableExceptions()yEnableExceptions()[YAPI EnableExceptions]yEnableExceptions()yEnableExceptions()YAPI.EnableExceptions()YAPI.EnableExceptions()YAPI.EnableExceptions()yEnableExceptions()YAPI.EnableExceptions()

Re-enables the use of exceptions for runtime error handling.

Be aware than when exceptions are enabled, every function that fails triggers an exception. If the exception is not caught by the user code, it either fires the debugger or aborts (i.e. crash) the program. On failure, throws an exception or returns a negative error code.

YAPI.EnableUSBHost()
yEnableUSBHost()YAPI.EnableUSBHost()

This function is used only on Android.

Before calling yRegisterHub("usb") you need to activate the USB host port of the system. This function takes as argument, an object of class android.content.Context (or any subclass). It is not necessary to call this function to reach modules through the network.

Parameters :

YAPI.FreeAPI()
yFreeAPI()yFreeAPI()yFreeAPI()[YAPI FreeAPI]yFreeAPI()yFreeAPI()YAPI.FreeAPI()YAPI.FreeAPI()YAPI.FreeAPI()YAPI.FreeAPI()yFreeAPI()YAPI.FreeAPI()

Frees dynamically allocated memory blocks used by the Yoctopuce library.

It is generally not required to call this function, unless you want to free all dynamically allocated memory blocks in order to track a memory leak for instance. You should not call any other library function after calling yFreeAPI(), or your program will crash.

YAPI.GetAPIVersion()
yGetAPIVersion()yGetAPIVersion()yGetAPIVersion()[YAPI GetAPIVersion]yGetAPIVersion()yGetAPIVersion()YAPI.GetAPIVersion()YAPI.GetAPIVersion()YAPI.GetAPIVersion()YAPI.GetAPIVersion()yGetAPIVersion()YAPI.GetAPIVersion()

Returns the version identifier for the Yoctopuce library in use.

The version is a string in the form "Major.Minor.Build", for instance "1.01.5535". For languages using an external DLL (for instance C#, VisualBasic or Delphi), the character string includes as well the DLL version, for instance "1.01.5535 (1.01.5439)".

If you want to verify in your code that the library version is compatible with the version that you have used during development, verify that the major number is strictly equal and that the minor number is greater or equal. The build number is not relevant with respect to the library compatibility.

Returns :

a character string describing the library version.

YAPI.GetCacheValidity()
yGetCacheValidity()yGetCacheValidity()[YAPI GetCacheValidity]yGetCacheValidity()yGetCacheValidity()YAPI.GetCacheValidity()YAPI.GetCacheValidity()YAPI.GetCacheValidity()YAPI.GetCacheValidity()yGetCacheValidity()YAPI.GetCacheValidity()

Returns the validity period of the data loaded by the library.

This method returns the cache validity of all attributes module functions. Note: This function must be called after yInitAPI .

Returns :

an integer corresponding to the validity attributed to the loaded function parameters, in milliseconds

YAPI.GetDeviceListValidity()
yGetDeviceListValidity()yGetDeviceListValidity()[YAPI GetDeviceListValidity]yGetDeviceListValidity()yGetDeviceListValidity()YAPI.GetDeviceListValidity()YAPI.GetDeviceListValidity()YAPI.GetDeviceListValidity()YAPI.GetDeviceListValidity()yGetDeviceListValidity()YAPI.GetDeviceListValidity()

Returns the time between each forced enumeration of the YoctoHub used.

Note: This function must be called after yInitAPI.

Returns :

the number of seconds between each enumeration.

YAPI.GetTickCount()
yGetTickCount()yGetTickCount()yGetTickCount()[YAPI GetTickCount]yGetTickCount()yGetTickCount()YAPI.GetTickCount()YAPI.GetTickCount()YAPI.GetTickCount()YAPI.GetTickCount()yGetTickCount()YAPI.GetTickCount()

Returns the current value of a monotone millisecond-based time counter.

This counter can be used to compute delays in relation with Yoctopuce devices, which also uses the millisecond as timebase.

Returns :

a long integer corresponding to the millisecond counter.

YAPI.HandleEvents()
yHandleEvents()yHandleEvents()yHandleEvents()[YAPI HandleEvents: ]yHandleEvents()yHandleEvents()YAPI.HandleEvents()YAPI.HandleEvents()YAPI.HandleEvents()YAPI.HandleEvents()yHandleEvents()YAPI.HandleEvents()

Maintains the device-to-library communication channel.

If your program includes significant loops, you may want to include a call to this function to make sure that the library takes care of the information pushed by the modules on the communication channels. This is not strictly necessary, but it may improve the reactivity of the library for the following commands.

This function may signal an error in case there is a communication problem while contacting a module.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.InitAPI()
yInitAPI()yInitAPI()yInitAPI()[YAPI InitAPI: ]yInitAPI()yInitAPI()YAPI.InitAPI()YAPI.InitAPI()YAPI.InitAPI()YAPI.InitAPI()yInitAPI()YAPI.InitAPI()

Initializes the Yoctopuce programming library explicitly.

It is not strictly needed to call yInitAPI(), as the library is automatically initialized when calling yRegisterHub() for the first time.

When Y_DETECT_NONE is used as detection mode, you must explicitly use yRegisterHub() to point the API to the VirtualHub on which your devices are connected before trying to access them.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.PreregisterHub()
yPreregisterHub()yPreregisterHub()yPreregisterHub()[YAPI PreregisterHub: ]yPreregisterHub()yPreregisterHub()YAPI.PreregisterHub()YAPI.PreregisterHub()YAPI.PreregisterHub()YAPI.PreregisterHub()yPreregisterHub()YAPI.PreregisterHub()

Fault-tolerant alternative to RegisterHub().

This function has the same purpose and same arguments as RegisterHub(), but does not trigger an error when the selected hub is not available at the time of the function call. This makes it possible to register a network hub independently of the current connectivity, and to try to contact it only when a device is actively needed.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.RegisterDeviceArrivalCallback()
yRegisterDeviceArrivalCallback()yRegisterDeviceArrivalCallback()yRegisterDeviceArrivalCallback()[YAPI RegisterDeviceArrivalCallback: ]yRegisterDeviceArrivalCallback()yRegisterDeviceArrivalCallback()YAPI.RegisterDeviceArrivalCallback()YAPI.RegisterDeviceArrivalCallback()YAPI.RegisterDeviceArrivalCallback()YAPI.RegisterDeviceArrivalCallback()yRegisterDeviceArrivalCallback()YAPI.RegisterDeviceArrivalCallback()

Register a callback function, to be called each time a device is plugged.

This callback will be invoked while yUpdateDeviceList is running. You will have to call this function on a regular basis.

Parameters :

YAPI.RegisterDeviceRemovalCallback()
yRegisterDeviceRemovalCallback()yRegisterDeviceRemovalCallback()yRegisterDeviceRemovalCallback()[YAPI RegisterDeviceRemovalCallback: ]yRegisterDeviceRemovalCallback()yRegisterDeviceRemovalCallback()YAPI.RegisterDeviceRemovalCallback()YAPI.RegisterDeviceRemovalCallback()YAPI.RegisterDeviceRemovalCallback()YAPI.RegisterDeviceRemovalCallback()yRegisterDeviceRemovalCallback()YAPI.RegisterDeviceRemovalCallback()

Register a callback function, to be called each time a device is unplugged.

This callback will be invoked while yUpdateDeviceList is running. You will have to call this function on a regular basis.

Parameters :

YAPI.RegisterHub()
yRegisterHub()yRegisterHub()yRegisterHub()[YAPI RegisterHub: ]yRegisterHub()yRegisterHub()YAPI.RegisterHub()YAPI.RegisterHub()YAPI.RegisterHub()YAPI.RegisterHub()yRegisterHub()YAPI.RegisterHub()

Setup the Yoctopuce library to use modules connected on a given machine.

The parameter will determine how the API will work. Use the following values:

usb: When the usb keyword is used, the API will work with devices connected directly to the USB bus. Some programming languages such a Javascript, PHP, and Java don't provide direct access to USB hardware, so usb will not work with these. In this case, use a VirtualHub or a networked YoctoHub (see below).

x.x.x.x or hostname: The API will use the devices connected to the host with the given IP address or hostname. That host can be a regular computer running a VirtualHub, or a networked YoctoHub such as YoctoHub-Ethernet or YoctoHub-Wireless. If you want to use the VirtualHub running on you local computer, use the IP address 127.0.0.1.

callback: that keyword make the API run in "HTTP Callback" mode. This a special mode allowing to take control of Yoctopuce devices through a NAT filter when using a VirtualHub or a networked YoctoHub. You only need to configure your hub to call your server script on a regular basis. This mode is currently available for PHP and Node.JS only.

Be aware that only one application can use direct USB access at a given time on a machine. Multiple access would cause conflicts while trying to access the USB modules. In particular, this means that you must stop the VirtualHub software before starting an application that uses direct USB access. The workaround for this limitation is to setup the library to use the VirtualHub rather than direct USB access.

If access control has been activated on the hub, virtual or not, you want to reach, the URL parameter should look like:

http://username:password@address:port

You can call RegisterHub several times to connect to several machines.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.RegisterHubDiscoveryCallback()
yRegisterHubDiscoveryCallback()yRegisterHubDiscoveryCallback()[YAPI RegisterHubDiscoveryCallback: ]yRegisterHubDiscoveryCallback()yRegisterHubDiscoveryCallback()YAPI.RegisterHubDiscoveryCallback()YAPI.RegisterHubDiscoveryCallback()YAPI.RegisterHubDiscoveryCallback()YAPI.RegisterHubDiscoveryCallback()

Register a callback function, to be called each time an Network Hub send an SSDP message.

The callback has two string parameter, the first one contain the serial number of the hub and the second contain the URL of the network hub (this URL can be passed to RegisterHub). This callback will be invoked while yUpdateDeviceList is running. You will have to call this function on a regular basis.

Parameters :

YAPI.RegisterHubWebsocketCallback()
yRegisterHubWebsocketCallback()

Variant to RegisterHub() used to initialize Yoctopuce API on an existing Websocket session, as happens for incoming websocket callbacks.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.RegisterLogFunction()
yRegisterLogFunction()yRegisterLogFunction()[YAPI RegisterLogFunction: ]yRegisterLogFunction()yRegisterLogFunction()YAPI.RegisterLogFunction()YAPI.RegisterLogFunction()YAPI.RegisterLogFunction()YAPI.RegisterLogFunction()

Registers a log callback function.

This callback will be called each time the API have something to say. Quite useful to debug the API.

Parameters :

YAPI.SelectArchitecture()
ySelectArchitecture()YAPI.SelectArchitecture()

Select the architecture or the library to be loaded to access to USB.

By default, the Python library automatically detects the appropriate library to use. However, for Linux ARM, it not possible to reliably distinguish between a Hard Float (armhf) and a Soft Float (armel) install. For in this case, it is therefore recommended to manually select the proper architecture by calling SelectArchitecture() before any other call to the library.

Parameters :

Returns :

nothing.

On failure, throws an exception.

YAPI.SetCacheValidity()
ySetCacheValidity()ySetCacheValidity()[YAPI SetCacheValidity: ]ySetCacheValidity()ySetCacheValidity()YAPI.SetCacheValidity()YAPI.SetCacheValidity()YAPI.SetCacheValidity()YAPI.SetCacheValidity()ySetCacheValidity()YAPI.SetCacheValidity()

Change the validity period of the data loaded by the library.

By default, when accessing a module, all the attributes of the module functions are automatically kept in cache for the standard duration (5 ms). This method can be used to change this standard duration, for example in order to reduce network or USB traffic. This parameter does not affect value change callbacks Note: This function must be called after yInitAPI.

Parameters :

YAPI.SetDelegate()
ySetDelegate()[YAPI SetDelegate: ]

(Objective-C only) Register an object that must follow the protocol YDeviceHotPlug.

The methods yDeviceArrival and yDeviceRemoval will be invoked while yUpdateDeviceList is running. You will have to call this function on a regular basis.

Parameters :

YAPI.SetDeviceListValidity()
ySetDeviceListValidity()ySetDeviceListValidity()[YAPI SetDeviceListValidity: ]ySetDeviceListValidity()ySetDeviceListValidity()YAPI.SetDeviceListValidity()YAPI.SetDeviceListValidity()YAPI.SetDeviceListValidity()YAPI.SetDeviceListValidity()ySetDeviceListValidity()YAPI.SetDeviceListValidity()

Change the time between each forced enumeration of the YoctoHub used.

By default, the library performs a complete enumeration every 10 seconds. To reduce network traffic it is possible to increase this delay. This is particularly useful when a YoctoHub is connected to a GSM network where the traffic is charged. This setting does not affect modules connected by USB, nor the operation of arrival/removal callbacks. Note: This function must be called after yInitAPI.

Parameters :

YAPI.SetHTTPCallbackCacheDir()
ySetHTTPCallbackCacheDir()ySetHTTPCallbackCacheDir()

Enables the HTTP callback cache.

When enabled, this cache reduces the quantity of data sent to the PHP script by 50% to 70%. To enable this cache, the method ySetHTTPCallbackCacheDir() must be called before any call to yRegisterHub(). This method takes in parameter the path of the directory used for saving data between each callback. This folder must exist and the PHP script needs to have write access to it. It is recommended to use a folder that is not published on the Web server since the library will save some data of Yoctopuce devices into this folder.

Note: This feature is supported by YoctoHub and VirtualHub since version 27750.

Parameters :

Returns :

nothing.

On failure, throws an exception.

YAPI.SetTimeout()
ySetTimeout()ySetTimeout()YAPI.SetTimeout()

Invoke the specified callback function after a given timeout.

This function behaves more or less like Javascript setTimeout, but during the waiting time, it will call yHandleEvents and yUpdateDeviceList periodically, in order to keep the API up-to-date with current devices.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.SetUSBPacketAckMs()
ySetUSBPacketAckMs()YAPI.SetUSBPacketAckMs()

Enables the acknowledge of every USB packet received by the Yoctopuce library.

This function allows the library to run on Android phones that tend to loose USB packets. By default, this feature is disabled because it doubles the number of packets sent and slows down the API considerably. Therefore, the acknowledge of incoming USB packets should only be enabled on phones or tablets that loose USB packets. A delay of 50 milliseconds is generally enough. In case of doubt, contact Yoctopuce support. To disable USB packets acknowledge, call this function with the value 0. Note: this feature is only available on Android.

Parameters :

YAPI.Sleep()
ySleep()ySleep()ySleep()[YAPI Sleep: ]ySleep()ySleep()YAPI.Sleep()YAPI.Sleep()YAPI.Sleep()YAPI.Sleep()ySleep()YAPI.Sleep()

Pauses the execution flow for a specified duration.

This function implements a passive waiting loop, meaning that it does not consume CPU cycles significantly. The processor is left available for other threads and processes. During the pause, the library nevertheless reads from time to time information from the Yoctopuce modules by calling yHandleEvents(), in order to stay up-to-date.

This function may signal an error in case there is a communication problem while contacting a module.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.TestHub()
yTestHub()yTestHub()[YAPI TestHub: ]yTestHub()yTestHub()YAPI.TestHub()YAPI.TestHub()YAPI.TestHub()YAPI.TestHub()yTestHub()YAPI.TestHub()

Test if the hub is reachable.

This method do not register the hub, it only test if the hub is usable. The url parameter follow the same convention as the RegisterHub method. This method is useful to verify the authentication parameters for a hub. It is possible to force this method to return after mstimeout milliseconds.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure returns a negative error code.

YAPI.TriggerHubDiscovery()
yTriggerHubDiscovery()yTriggerHubDiscovery()[YAPI TriggerHubDiscovery: ]yTriggerHubDiscovery()yTriggerHubDiscovery()YAPI.TriggerHubDiscovery()YAPI.TriggerHubDiscovery()YAPI.TriggerHubDiscovery()YAPI.TriggerHubDiscovery()

Force a hub discovery, if a callback as been registered with yRegisterHubDiscoveryCallback it will be called for each net work hub that will respond to the discovery.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds. On failure, throws an exception or returns a negative error code.

YAPI.UnregisterHub()
yUnregisterHub()yUnregisterHub()yUnregisterHub()[YAPI UnregisterHub: ]yUnregisterHub()yUnregisterHub()YAPI.UnregisterHub()YAPI.UnregisterHub()YAPI.UnregisterHub()YAPI.UnregisterHub()yUnregisterHub()YAPI.UnregisterHub()

Setup the Yoctopuce library to no more use modules connected on a previously registered machine with RegisterHub.

Parameters :

YAPI.UpdateDeviceList()
yUpdateDeviceList()yUpdateDeviceList()yUpdateDeviceList()[YAPI UpdateDeviceList: ]yUpdateDeviceList()yUpdateDeviceList()YAPI.UpdateDeviceList()YAPI.UpdateDeviceList()YAPI.UpdateDeviceList()YAPI.UpdateDeviceList()yUpdateDeviceList()YAPI.UpdateDeviceList()

Triggers a (re)detection of connected Yoctopuce modules.

The library searches the machines or USB ports previously registered using yRegisterHub(), and invokes any user-defined callback function in case a change in the list of connected devices is detected.

This function can be called as frequently as desired to refresh the device list and to make the application aware of hot-plug events.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

YAPI.UpdateDeviceList_async()
yUpdateDeviceList_async()yUpdateDeviceList_async()

Triggers a (re)detection of connected Yoctopuce modules.

The library searches the machines or USB ports previously registered using yRegisterHub(), and invokes any user-defined callback function in case a change in the list of connected devices is detected.

This function can be called as frequently as desired to refresh the device list and to make the application aware of hot-plug events.

This asynchronous version exists only in Javascript. It uses a callback instead of a return value in order to avoid blocking Firefox Javascript VM that does not implement context switching during blocking I/O calls.

Parameters :

Returns :

nothing : the result is provided to the callback.

21.2. Module control interface

This interface is identical for all Yoctopuce USB modules. It can be used to control the module global parameters, and to enumerate the functions provided by each module.

Global functions
yFindModule(func)
Allows you to find a module from its serial number or from its logical name.
yFindModuleInContext(yctx, func)
Retrieves a module for a given identifier in a YAPI context.
yFirstModule()
Starts the enumeration of modules currently accessible.
YModule methods
module→checkFirmware(path, onlynew)
Tests whether the byn file is valid for this module.
module→clearCache()
Invalidates the cache.
module→describe()
Returns a descriptive text that identifies the module.
module→download(pathname)
Downloads the specified built-in file and returns a binary buffer with its content.
module→functionBaseType(functionIndex)
Retrieves the base type of the nth function on the module.
module→functionCount()
Returns the number of functions (beside the "module" interface) available on the module.
module→functionId(functionIndex)
Retrieves the hardware identifier of the nth function on the module.
module→functionName(functionIndex)
Retrieves the logical name of the nth function on the module.
module→functionType(functionIndex)
Retrieves the type of the nth function on the module.
module→functionValue(functionIndex)
Retrieves the advertised value of the nth function on the module.
module→get_allSettings()
Returns all the settings and uploaded files of the module.
module→get_beacon()
Returns the state of the localization beacon.
module→get_errorMessage()
Returns the error message of the latest error with this module object.
module→get_errorType()
Returns the numerical error code of the latest error with this module object.
module→get_firmwareRelease()
Returns the version of the firmware embedded in the module.
module→get_functionIds(funType)
Retrieve all hardware identifier that match the type passed in argument.
module→get_hardwareId()
Returns the unique hardware identifier of the module.
module→get_icon2d()
Returns the icon of the module.
module→get_lastLogs()
Returns a string with last logs of the module.
module→get_logicalName()
Returns the logical name of the module.
module→get_luminosity()
Returns the luminosity of the module informative leds (from 0 to 100).
module→get_parentHub()
Returns the serial number of the YoctoHub on which this module is connected.
module→get_persistentSettings()
Returns the current state of persistent module settings.
module→get_productId()
Returns the USB device identifier of the module.
module→get_productName()
Returns the commercial name of the module, as set by the factory.
module→get_productRelease()
Returns the hardware release version of the module.
module→get_rebootCountdown()
Returns the remaining number of seconds before the module restarts, or zero when no reboot has been scheduled.
module→get_serialNumber()
Returns the serial number of the module, as set by the factory.
module→get_subDevices()
Returns a list of all the modules that are plugged into the current module.
module→get_upTime()
Returns the number of milliseconds spent since the module was powered on.
module→get_url()
Returns the URL used to access the module.
module→get_usbCurrent()
Returns the current consumed by the module on the USB bus, in milli-amps.
module→get_userData()
Returns the value of the userData attribute, as previously stored using method set_userData.
module→get_userVar()
Returns the value previously stored in this attribute.
module→hasFunction(funcId)
Tests if the device includes a specific function.
module→isOnline()
Checks if the module is currently reachable, without raising any error.
module→isOnline_async(callback, context)
Checks if the module is currently reachable, without raising any error.
module→load(msValidity)
Preloads the module cache with a specified validity duration.
module→load_async(msValidity, callback, context)
Preloads the module cache with a specified validity duration (asynchronous version).
module→log(text)
Adds a text message to the device logs.
module→nextModule()
Continues the module enumeration started using yFirstModule().
module→reboot(secBeforeReboot)
Schedules a simple module reboot after the given number of seconds.
module→registerBeaconCallback(callback)
Register a callback function, to be called when the localization beacon of the module has been changed.
module→registerConfigChangeCallback(callback)
Register a callback function, to be called when a persistent settings in a device configuration has been changed (e.g.
module→registerLogCallback(callback)
Registers a device log callback function.
module→revertFromFlash()
Reloads the settings stored in the nonvolatile memory, as when the module is powered on.
module→saveToFlash()
Saves current settings in the nonvolatile memory of the module.
module→set_allSettings(settings)
Restores all the settings of the device.
module→set_allSettingsAndFiles(settings)
Restores all the settings and uploaded files to the module.
module→set_beacon(newval)
Turns on or off the module localization beacon.
module→set_logicalName(newval)
Changes the logical name of the module.
module→set_luminosity(newval)
Changes the luminosity of the module informative leds.
module→set_userData(data)
Stores a user context provided as argument in the userData attribute of the function.
module→set_userVar(newval)
Stores a 32 bit value in the device RAM.
module→triggerConfigChangeCallback()
Triggers a configuration change callback, to check if they are supported or not.
module→triggerFirmwareUpdate(secBeforeReboot)
Schedules a module reboot into special firmware update mode.
module→updateFirmware(path)
Prepares a firmware update of the module.
module→updateFirmwareEx(path, force)
Prepares a firmware update of the module.
module→wait_async(callback, context)
Waits for all pending asynchronous commands on the module to complete, and invoke the user-provided callback function.

YModule.FindModule()
yFindModule()yFindModule()yFindModule()[YModule FindModule: ]yFindModule()yFindModule()YModule.FindModule()YModule.FindModule()YModule.FindModule()YModule.FindModule()yFindModule()YModule.FindModule()

Allows you to find a module from its serial number or from its logical name.

This function does not require that the module is online at the time it is invoked. The returned object is nevertheless valid. Use the method YModule.isOnline() to test if the module is indeed online at a given time. In case of ambiguity when looking for a module by logical name, no error is notified: the first instance found is returned. The search is performed first by hardware name, then by logical name.

If a call to this object's is_online() method returns FALSE although you are certain that the device is plugged, make sure that you did call registerHub() at application initialization time.

Parameters :

Returns :

a YModule object allowing you to drive the module or get additional information on the module.

YModule.FindModuleInContext()
yFindModuleInContext()YModule.FindModuleInContext()YModule.FindModuleInContext()YModule.FindModuleInContext()

Retrieves a module for a given identifier in a YAPI context.

The identifier can be specified using several formats:

• FunctionLogicalName
• ModuleSerialNumber.FunctionIdentifier
• ModuleSerialNumber.FunctionLogicalName
• ModuleLogicalName.FunctionIdentifier
• ModuleLogicalName.FunctionLogicalName

This function does not require that the module is online at the time it is invoked. The returned object is nevertheless valid. Use the method YModule.isOnline() to test if the module is indeed online at a given time. In case of ambiguity when looking for a module by logical name, no error is notified: the first instance found is returned. The search is performed first by hardware name, then by logical name.

Parameters :

Returns :

a YModule object allowing you to drive the module.

YModule.FirstModule()
yFirstModule()yFirstModule()yFirstModule()[YModule FirstModule]yFirstModule()yFirstModule()YModule.FirstModule()YModule.FirstModule()YModule.FirstModule()YModule.FirstModule()yFirstModule()YModule.FirstModule()

Starts the enumeration of modules currently accessible.

Use the method YModule.nextModule() to iterate on the next modules.

Returns :

a pointer to a YModule object, corresponding to the first module currently online, or a null pointer if there are none.

module→checkFirmware()module.checkFirmware()module→checkFirmware()[module checkFirmware: ]module.checkFirmware()module.checkFirmware()module.checkFirmware()module.checkFirmware()module.checkFirmware()module.checkFirmware()module→checkFirmware()module.checkFirmware()YModule checkFirmware

Tests whether the byn file is valid for this module.

This method is useful to test if the module needs to be updated. It is possible to pass a directory as argument instead of a file. In this case, this method returns the path of the most recent appropriate .byn file. If the parameter onlynew is true, the function discards firmwares that are older or equal to the installed firmware.

Parameters :

Returns :

the path of the byn file to use or a empty string if no byn files matches the requirement

On failure, throws an exception or returns a string that start with "error:".

module→clearCache()module.clearCache()module→clearCache()[module clearCache]module.clearCache()module.clearCache()module.clearCache()module.clearCache()module.clearCache()module→clearCache()module.clearCache()

Invalidates the cache.

Invalidates the cache of the module attributes. Forces the next call to get_xxx() or loadxxx() to use values that come from the device.

module→describe()module.describe()module→describe()[module describe]module.describe()module.describe()module.describe()module.describe()module.describe()module→describe()module.describe()

Returns a descriptive text that identifies the module.

The text may include either the logical name or the serial number of the module.

Returns :

a string that describes the module

module→download()module.download()module→download()[module download: ]module.download()module.download()module.download()module.download()module.download()module.download()module→download()module.download()YModule download

Downloads the specified built-in file and returns a binary buffer with its content.

Parameters :

Returns :

a binary buffer with the file content

On failure, throws an exception or returns YAPI_INVALID_STRING.

module→functionBaseType()module.functionBaseType()module→functionBaseType()module.functionBaseType()module.functionBaseType()module.functionBaseType()module.functionBaseType()module.functionBaseType()module→functionBaseType()module.functionBaseType()

Retrieves the base type of the nth function on the module.

For instance, the base type of all measuring functions is "Sensor".

Parameters :

Returns :

a string corresponding to the base type of the function

On failure, throws an exception or returns an empty string.

module→functionCount()module.functionCount()module→functionCount()[module functionCount]module.functionCount()module.functionCount()module.functionCount()module.functionCount()module.functionCount()module→functionCount()module.functionCount()

Returns the number of functions (beside the "module" interface) available on the module.

Returns :

the number of functions on the module

On failure, throws an exception or returns a negative error code.

module→functionId()module.functionId()module→functionId()[module functionId: ]module.functionId()module.functionId()module.functionId()module.functionId()module.functionId()module→functionId()module.functionId()

Retrieves the hardware identifier of the nth function on the module.

Parameters :

Returns :

a string corresponding to the unambiguous hardware identifier of the requested module function

On failure, throws an exception or returns an empty string.

module→functionName()module.functionName()module→functionName()[module functionName: ]module.functionName()module.functionName()module.functionName()module.functionName()module.functionName()module→functionName()module.functionName()

Retrieves the logical name of the nth function on the module.

Parameters :

Returns :

a string corresponding to the logical name of the requested module function

On failure, throws an exception or returns an empty string.

module→functionType()module.functionType()module→functionType()module.functionType()module.functionType()module.functionType()module.functionType()module.functionType()module→functionType()module.functionType()

Retrieves the type of the nth function on the module.

Parameters :

Returns :

a string corresponding to the type of the function

On failure, throws an exception or returns an empty string.

module→functionValue()module.functionValue()module→functionValue()[module functionValue: ]module.functionValue()module.functionValue()module.functionValue()module.functionValue()module.functionValue()module→functionValue()module.functionValue()

Retrieves the advertised value of the nth function on the module.

Parameters :

Returns :

a short string (up to 6 characters) corresponding to the advertised value of the requested module function

On failure, throws an exception or returns an empty string.

module→get_allSettings()
module→allSettings()module.get_allSettings()module→get_allSettings()[module allSettings]module.get_allSettings()module.get_allSettings()module.get_allSettings()module.get_allSettings()module.get_allSettings()module.get_allSettings()module→get_allSettings()module.get_allSettings()YModule get_allSettings

Returns all the settings and uploaded files of the module.

Useful to backup all the logical names, calibrations parameters, and uploaded files of a device.

Returns :

a binary buffer with all the settings.

On failure, throws an exception or returns an binary object of size 0.

module→get_beacon()
module→beacon()module.get_beacon()module→get_beacon()[module beacon]module.get_beacon()module.get_beacon()module.get_beacon()module.get_beacon()module.get_beacon()module.get_beacon()module→get_beacon()module.get_beacon()YModule get_beacon

Returns the state of the localization beacon.

Returns :

either Y_BEACON_OFF or Y_BEACON_ON, according to the state of the localization beacon

On failure, throws an exception or returns Y_BEACON_INVALID.

module→get_errorMessage()
module→errorMessage()module.get_errorMessage()module→get_errorMessage()[module errorMessage]module.get_errorMessage()module.get_errorMessage()module.get_errorMessage()module.get_errorMessage()module.get_errorMessage()module→get_errorMessage()module.get_errorMessage()

Returns the error message of the latest error with this module object.

This method is mostly useful when using the Yoctopuce library with exceptions disabled.

Returns :

a string corresponding to the latest error message that occured while using this module object

module→get_errorType()
module→errorType()module.get_errorType()module→get_errorType()module.get_errorType()module.get_errorType()module.get_errorType()module.get_errorType()module.get_errorType()module→get_errorType()module.get_errorType()

Returns the numerical error code of the latest error with this module object.

This method is mostly useful when using the Yoctopuce library with exceptions disabled.

Returns :

a number corresponding to the code of the latest error that occurred while using this module object

module→get_firmwareRelease()
module→firmwareRelease()module.get_firmwareRelease()module→get_firmwareRelease()[module firmwareRelease]module.get_firmwareRelease()module.get_firmwareRelease()module.get_firmwareRelease()module.get_firmwareRelease()module.get_firmwareRelease()module.get_firmwareRelease()module→get_firmwareRelease()module.get_firmwareRelease()YModule get_firmwareRelease

Returns the version of the firmware embedded in the module.

Returns :

a string corresponding to the version of the firmware embedded in the module

On failure, throws an exception or returns Y_FIRMWARERELEASE_INVALID.

module→get_functionIds()
module→functionIds()module.get_functionIds()module→get_functionIds()[module functionIds: ]module.get_functionIds()module.get_functionIds()module.get_functionIds()module.get_functionIds()module.get_functionIds()module.get_functionIds()module→get_functionIds()module.get_functionIds()YModule get_functionIds

Retrieve all hardware identifier that match the type passed in argument.

Parameters :

Returns :

an array of strings.

module→get_hardwareId()
module→hardwareId()module.get_hardwareId()module→get_hardwareId()[module hardwareId]module.get_hardwareId()module.get_hardwareId()module.get_hardwareId()module.get_hardwareId()module→get_hardwareId()module.get_hardwareId()

Returns the unique hardware identifier of the module.

The unique hardware identifier is made of the device serial number followed by string ".module".

Returns :

a string that uniquely identifies the module

module→get_icon2d()
module→icon2d()module.get_icon2d()module→get_icon2d()[module icon2d]module.get_icon2d()module.get_icon2d()module.get_icon2d()module.get_icon2d()module.get_icon2d()module.get_icon2d()module→get_icon2d()module.get_icon2d()YModule get_icon2d

Returns the icon of the module.

The icon is a PNG image and does not exceeds 1536 bytes.

Returns :

a binary buffer with module icon, in png format. On failure, throws an exception or returns YAPI_INVALID_STRING.

module→get_lastLogs()
module→lastLogs()module.get_lastLogs()module→get_lastLogs()[module lastLogs]module.get_lastLogs()module.get_lastLogs()module.get_lastLogs()module.get_lastLogs()module.get_lastLogs()module.get_lastLogs()module→get_lastLogs()module.get_lastLogs()YModule get_lastLogs

Returns a string with last logs of the module.

This method return only logs that are still in the module.

Returns :

a string with last logs of the module. On failure, throws an exception or returns YAPI_INVALID_STRING.

module→get_logicalName()
module→logicalName()module.get_logicalName()module→get_logicalName()[module logicalName]module.get_logicalName()module.get_logicalName()module.get_logicalName()module.get_logicalName()module.get_logicalName()module.get_logicalName()module→get_logicalName()module.get_logicalName()YModule get_logicalName

Returns the logical name of the module.

Returns :

a string corresponding to the logical name of the module

On failure, throws an exception or returns Y_LOGICALNAME_INVALID.

module→get_luminosity()
module→luminosity()module.get_luminosity()module→get_luminosity()[module luminosity]module.get_luminosity()module.get_luminosity()module.get_luminosity()module.get_luminosity()module.get_luminosity()module.get_luminosity()module→get_luminosity()module.get_luminosity()YModule get_luminosity

Returns the luminosity of the module informative leds (from 0 to 100).

Returns :

an integer corresponding to the luminosity of the module informative leds (from 0 to 100)

On failure, throws an exception or returns Y_LUMINOSITY_INVALID.

module→get_parentHub()
module→parentHub()module.get_parentHub()module→get_parentHub()[module parentHub]module.get_parentHub()module.get_parentHub()module.get_parentHub()module.get_parentHub()module.get_parentHub()module.get_parentHub()module→get_parentHub()module.get_parentHub()YModule get_parentHub

Returns the serial number of the YoctoHub on which this module is connected.

If the module is connected by USB, or if the module is the root YoctoHub, an empty string is returned.

Returns :

a string with the serial number of the YoctoHub or an empty string

module→get_persistentSettings()
module→persistentSettings()module.get_persistentSettings()module→get_persistentSettings()[module persistentSettings]module.get_persistentSettings()module.get_persistentSettings()module.get_persistentSettings()module.get_persistentSettings()module.get_persistentSettings()module.get_persistentSettings()module→get_persistentSettings()module.get_persistentSettings()YModule get_persistentSettings

Returns the current state of persistent module settings.

Returns :

a value among Y_PERSISTENTSETTINGS_LOADED, Y_PERSISTENTSETTINGS_SAVED and Y_PERSISTENTSETTINGS_MODIFIED corresponding to the current state of persistent module settings

On failure, throws an exception or returns Y_PERSISTENTSETTINGS_INVALID.

module→get_productId()
module→productId()module.get_productId()module→get_productId()[module productId]module.get_productId()module.get_productId()module.get_productId()module.get_productId()module.get_productId()module.get_productId()module→get_productId()module.get_productId()YModule get_productId

Returns the USB device identifier of the module.

Returns :

an integer corresponding to the USB device identifier of the module

On failure, throws an exception or returns Y_PRODUCTID_INVALID.

module→get_productName()
module→productName()module.get_productName()module→get_productName()[module productName]module.get_productName()module.get_productName()module.get_productName()module.get_productName()module.get_productName()module.get_productName()module→get_productName()module.get_productName()YModule get_productName

Returns the commercial name of the module, as set by the factory.

Returns :

a string corresponding to the commercial name of the module, as set by the factory

On failure, throws an exception or returns Y_PRODUCTNAME_INVALID.

module→get_productRelease()
module→productRelease()module.get_productRelease()module→get_productRelease()[module productRelease]module.get_productRelease()module.get_productRelease()module.get_productRelease()module.get_productRelease()module.get_productRelease()module.get_productRelease()module→get_productRelease()module.get_productRelease()YModule get_productRelease

Returns the hardware release version of the module.

Returns :

an integer corresponding to the hardware release version of the module

On failure, throws an exception or returns Y_PRODUCTRELEASE_INVALID.

module→get_rebootCountdown()
module→rebootCountdown()module.get_rebootCountdown()module→get_rebootCountdown()[module rebootCountdown]module.get_rebootCountdown()module.get_rebootCountdown()module.get_rebootCountdown()module.get_rebootCountdown()module.get_rebootCountdown()module.get_rebootCountdown()module→get_rebootCountdown()module.get_rebootCountdown()YModule get_rebootCountdown

Returns the remaining number of seconds before the module restarts, or zero when no reboot has been scheduled.

Returns :

an integer corresponding to the remaining number of seconds before the module restarts, or zero when no reboot has been scheduled

On failure, throws an exception or returns Y_REBOOTCOUNTDOWN_INVALID.

module→get_serialNumber()
module→serialNumber()module.get_serialNumber()module→get_serialNumber()[module serialNumber]module.get_serialNumber()module.get_serialNumber()module.get_serialNumber()module.get_serialNumber()module.get_serialNumber()module.get_serialNumber()module→get_serialNumber()module.get_serialNumber()YModule get_serialNumber

Returns the serial number of the module, as set by the factory.

Returns :

a string corresponding to the serial number of the module, as set by the factory

On failure, throws an exception or returns Y_SERIALNUMBER_INVALID.

module→get_subDevices()
module→subDevices()module.get_subDevices()module→get_subDevices()[module subDevices]module.get_subDevices()module.get_subDevices()module.get_subDevices()module.get_subDevices()module.get_subDevices()module.get_subDevices()module→get_subDevices()module.get_subDevices()YModule get_subDevices

Returns a list of all the modules that are plugged into the current module.

This method only makes sense when called for a YoctoHub/VirtualHub. Otherwise, an empty array will be returned.

Returns :

an array of strings containing the sub modules.

module→get_upTime()
module→upTime()module.get_upTime()module→get_upTime()[module upTime]module.get_upTime()module.get_upTime()module.get_upTime()module.get_upTime()module.get_upTime()module.get_upTime()module→get_upTime()module.get_upTime()YModule get_upTime

Returns the number of milliseconds spent since the module was powered on.

Returns :

an integer corresponding to the number of milliseconds spent since the module was powered on

On failure, throws an exception or returns Y_UPTIME_INVALID.

module→get_url()
module→url()module.get_url()module→get_url()[module url]module.get_url()module.get_url()module.get_url()module.get_url()module.get_url()module.get_url()module→get_url()module.get_url()YModule get_url

Returns the URL used to access the module.

If the module is connected by USB, the string 'usb' is returned.

Returns :

a string with the URL of the module.

module→get_usbCurrent()
module→usbCurrent()module.get_usbCurrent()module→get_usbCurrent()[module usbCurrent]module.get_usbCurrent()module.get_usbCurrent()module.get_usbCurrent()module.get_usbCurrent()module.get_usbCurrent()module.get_usbCurrent()module→get_usbCurrent()module.get_usbCurrent()YModule get_usbCurrent

Returns the current consumed by the module on the USB bus, in milli-amps.

Returns :

an integer corresponding to the current consumed by the module on the USB bus, in milli-amps

On failure, throws an exception or returns Y_USBCURRENT_INVALID.

module→get_userData()
module→userData()module.get_userData()module→get_userData()[module userData]module.get_userData()module.get_userData()module.get_userData()module.get_userData()module.get_userData()module→get_userData()module.get_userData()

Returns the value of the userData attribute, as previously stored using method set_userData.

This attribute is never touched directly by the API, and is at disposal of the caller to store a context.

Returns :

the object stored previously by the caller.

module→get_userVar()
module→userVar()module.get_userVar()module→get_userVar()[module userVar]module.get_userVar()module.get_userVar()module.get_userVar()module.get_userVar()module.get_userVar()module.get_userVar()module→get_userVar()module.get_userVar()YModule get_userVar

Returns the value previously stored in this attribute.

On startup and after a device reboot, the value is always reset to zero.

Returns :

an integer corresponding to the value previously stored in this attribute

On failure, throws an exception or returns Y_USERVAR_INVALID.

module→hasFunction()module.hasFunction()module→hasFunction()[module hasFunction: ]module.hasFunction()module.hasFunction()module.hasFunction()module.hasFunction()module.hasFunction()module.hasFunction()module→hasFunction()module.hasFunction()YModule hasFunction

Tests if the device includes a specific function.

This method takes a function identifier and returns a boolean.

Parameters :

Returns :

true if the device has the function identifier

module→isOnline()module.isOnline()module→isOnline()[module isOnline]module.isOnline()module.isOnline()module.isOnline()module.isOnline()module.isOnline()module→isOnline()module.isOnline()

Checks if the module is currently reachable, without raising any error.

If there are valid cached values for the module, that have not yet expired, the device is considered reachable. No exception is raised if there is an error while trying to contact the requested module.

Returns :

true if the module can be reached, and false otherwise

module→isOnline_async()module.isOnline_async()

Checks if the module is currently reachable, without raising any error.

If there are valid cached values for the module, that have not yet expired, the device is considered reachable. No exception is raised if there is an error while trying to contact the requested module.

This asynchronous version exists only in Javascript. It uses a callback instead of a return value in order to avoid blocking Firefox Javascript VM that does not implement context switching during blocking I/O calls.

Parameters :

Returns :

nothing : the result is provided to the callback.

module→load()module.load()module→load()[module load: ]module.load()module.load()module.load()module.load()module.load()module→load()module.load()

Preloads the module cache with a specified validity duration.

By default, whenever accessing a device, all module attributes are kept in cache for the standard duration (5 ms). This method can be used to temporarily mark the cache as valid for a longer period, in order to reduce network traffic for instance.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

module→load_async()module.load_async()

Preloads the module cache with a specified validity duration (asynchronous version).

By default, whenever accessing a device, all module attributes are kept in cache for the standard duration (5 ms). This method can be used to temporarily mark the cache as valid for a longer period, in order to reduce network traffic for instance.

This asynchronous version exists only in Javascript. It uses a callback instead of a return value in order to avoid blocking Firefox javascript VM that does not implement context switching during blocking I/O calls. See the documentation section on asynchronous Javascript calls for more details.

Parameters :

Returns :

nothing : the result is provided to the callback.

module→log()module.log()module→log()[module log: ]module.log()module.log()module.log()module.log()module.log()module.log()module→log()module.log()YModule log

Adds a text message to the device logs.

This function is useful in particular to trace the execution of HTTP callbacks. If a newline is desired after the message, it must be included in the string.

Parameters :

Returns :

YAPI_SUCCESS if the call succeeds.

On failure, throws an exception or returns a negative error code.

module→nextModule()module.nextModule()module→nextModule()[module nextModule]module.nextModule()module.nextModule()module.nextModule()module.nextModule()module.nextModule()module.nextModule()module→nextModule()module.nextModule()

Continues the module enumeration started using yFirstModule().

Returns :

a pointer to a YModule object, corresponding to the next module found, or a null pointer if there are no more modules to enumerate.

module→reboot()module.reboot()module→reboot()[module reboot: ]module.reboot()module.reboot()module.reboot()module.reboot()module.reboot()module.reboot()module→reboot()module.reboot()YModule reboot

Schedules a simple module reboot after the given number of seconds.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

module→registerBeaconCallback()module.registerBeaconCallback()module→registerBeaconCallback()[module registerBeaconCallback: ]module.registerBeaconCallback()module.registerBeaconCallback()module.registerBeaconCallback()module.registerBeaconCallback()module.registerBeaconCallback()module.registerBeaconCallback()module→registerBeaconCallback()module.registerBeaconCallback()

Register a callback function, to be called when the localization beacon of the module has been changed.

The callback function should take two arguments: the YModule object of which the beacon has changed, and an integer describing the new beacon state.

Parameters :

module→registerConfigChangeCallback()module.registerConfigChangeCallback()module→registerConfigChangeCallback()[module registerConfigChangeCallback: ]module.registerConfigChangeCallback()module.registerConfigChangeCallback()module.registerConfigChangeCallback()module.registerConfigChangeCallback()module.registerConfigChangeCallback()module.registerConfigChangeCallback()module→registerConfigChangeCallback()module.registerConfigChangeCallback()

Register a callback function, to be called when a persistent settings in a device configuration has been changed (e.g.

change of unit, etc).

Parameters :

module→registerLogCallback()module→registerLogCallback()[module registerLogCallback: ]module.registerLogCallback()module.registerLogCallback()module.registerLogCallback()module.registerLogCallback()

Registers a device log callback function.

This callback will be called each time that a module sends a new log message. Mostly useful to debug a Yoctopuce module.

Parameters :

module→revertFromFlash()module.revertFromFlash()module→revertFromFlash()[module revertFromFlash]module.revertFromFlash()module.revertFromFlash()module.revertFromFlash()module.revertFromFlash()module.revertFromFlash()module.revertFromFlash()module→revertFromFlash()module.revertFromFlash()YModule revertFromFlash

Reloads the settings stored in the nonvolatile memory, as when the module is powered on.

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

module→saveToFlash()module.saveToFlash()module→saveToFlash()[module saveToFlash]module.saveToFlash()module.saveToFlash()module.saveToFlash()module.saveToFlash()module.saveToFlash()module.saveToFlash()module→saveToFlash()module.saveToFlash()YModule saveToFlash

Saves current settings in the nonvolatile memory of the module.

Warning: the number of allowed save operations during a module life is limited (about 100000 cycles). Do not call this function within a loop.

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

module→set_allSettings()
module→setAllSettings()module.set_allSettings()module→set_allSettings()[module setAllSettings: ]module.set_allSettings()module.set_allSettings()module.set_allSettings()module.set_allSettings()module.set_allSettings()module.set_allSettings()module→set_allSettings()module.set_allSettings()YModule set_allSettings

Restores all the settings of the device.

Useful to restore all the logical names and calibrations parameters of a module from a backup.Remember to call the saveToFlash() method of the module if the modifications must be kept.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

module→set_allSettingsAndFiles()
module→setAllSettingsAndFiles()module.set_allSettingsAndFiles()module→set_allSettingsAndFiles()[module setAllSettingsAndFiles: ]module.set_allSettingsAndFiles()module.set_allSettingsAndFiles()module.set_allSettingsAndFiles()module.set_allSettingsAndFiles()module.set_allSettingsAndFiles()module.set_allSettingsAndFiles()module→set_allSettingsAndFiles()module.set_allSettingsAndFiles()YModule set_allSettingsAndFiles

Restores all the settings and uploaded files to the module.

This method is useful to restore all the logical names and calibrations parameters, uploaded files etc. of a device from a backup. Remember to call the saveToFlash() method of the module if the modifications must be kept.

Parameters :

Returns :

YAPI_SUCCESS when the call succeeds.

On failure, throws an exception or returns a negative error code.

module→set_beacon()
module→setBeacon()module.set_beacon()module→set_beacon()[module setBeacon: ]module.set_beacon()module.set_beacon()module.set_beacon()module.set_beacon()module.set_beacon()module.set_beacon()module→set_beacon()module.set_beacon()YModule set_beacon

Turns on or off the module localization beacon.

Parameters :

Returns :

YAPI_SUCCESS if the call succeeds.

On failure, throws an exception or returns a negative error code.

module→set_logicalName()
module→setLogicalName()module.set_logicalName()module→set_logicalName()[module setLogicalName: ]module.set_logicalName()module.set_logicalName()module.set_logicalName()module.set_logicalName()module.set_logicalName()module.set_logicalName()module→set_logicalName()module.set_logicalName()YModule set_logicalName

Changes the logical name of the module.

You can use yCheckLogicalName() prior to this call to make sure that your parameter is valid. Remember to call the saveToFlash() method of the module if the modification must be kept.

Parameters :

Returns :

YAPI_SUCCESS if the call succeeds.

On failure, throws an exception or returns a negative error code.

module→set_luminosity()
module→setLuminosity()module.set_luminosity()module→set_luminosity()[module setLuminosity: ]module.set_luminosity()module.set_luminosity()module.set_luminosity()module.set_luminosity()module.set_luminosity()module.set_luminosity()module→set_luminosity()module.set_luminosity()YModule set_luminosity

Changes the luminosity of the module informative leds.

The parameter is a value between 0 and 100. Remember to call the saveToFlash() method of the module if the modification must be kept.

Parameters :