New ! The Yocto-RS232

New ! The Yocto-RS232

This week, we are presenting the Yocto-RS232. This project was in and about for a while, but because of a recent increase in the demand for this kind of module, we at last decided to complete it. The Yocto-RS232 has a hard duty: to simplify your life to access anything with an RS232 interface. You must be thinking that FTDI has been doing this very well for a long time... Maybe, but the Yocto-RS232 may open up your eyes to new horizons.

The Yocto-RS232.
The Yocto-RS232.

What is the Yocto-RS232?

The Yocto-RS232 is a USB to RS232 gateway. As any Yoctopuce product, you don't need any driver to use it, and its use doesn't even require any virtual COM port. You are done with the hunt for the correct drivers and with COM ports changing names... :-) Physically, the Yocto-RS232 is a 20*60mm board with an RJ11 connector. An RJ11 to DB9 cable is provided with it. There was simply not enough space on the board to put a DB9 connector directly on it.

The RJ11/DB9 cable is provided
The RJ11/DB9 cable is provided

It's also an isolated module. There is a galvanic isolation between the USB part and the RS232 part. This enables you to connect machines powered on a different electric circuit without risking to fry the PC or the machine.


The Yocto-RS232 is a complete serial port: It has RX, TX, RTS, and CTS lines. In addition to byte streams, it can natively manage several types of message-based serial protocols:

  • Line-based ASCII: the most classical use of serial ports. The module sends and reads strings of ASCII characters on the line.
  • Framed-based binary: The module sends and reads binary frames, separated by short pauses.
  • MODBUS ASCII: The module can generate ASCII encoded MODBUS commands.
  • MODBUS RTU: The module can generate binary encoded MODBUS commands.

The Yocto-RS232 has its own buffers enabling it to temporarily store data while waiting for them to be consumed. If the control computer restarts, communication can recover without data loss. It seems like nothing, but in some cases it makes a real difference.

Sensor interface

The Yocto-RS232 is much more than any regular USB to RS232 gateway. It was designed mostly to interface serial sensors. It can autonomously interpret data coming out of a serial device and present them as a YGenericSensor sensor. It even has a data logger enabling it to store these measures internally.

How does it work? You must configure the module with a short script telling it how to interpret the serial data and that's it! The VirtualHub even provides you with a small interface to create these scripts intuitively.

Script creation interface
Script creation interface

What's the interest compared to using a classic USB to serial adapter? You can potentially transform any device with a serial output into a Yoctopuce sensor and thus benefit from all the advantages provided by the Yoctopuce API: polling, callback, data logger, and so on... Icing on the cake, if you add to it a YoctoHub-Ethernet or a YoctoHub-Wireless-g, you can access your device through the network. Neat, isn't it ? :-)

Adding a network interface to a serial device? Easy as pie!
Adding a network interface to a serial device? Easy as pie!


The Yocto-RS232 can also work as a snooper and record data going through a serial cable without interfering with the communications. This enables you to build a cheap serial communication analyzer. A simple way to reverse engineer communications between a device and its control application, some manufacturers having the bad habit to forget to document their protocols.

What the Yocto-RS232 is not

Beware, the Yocto-RS232 is not a classic USB/serial interface. It doesn't install a virtual COM port, so it can't be used to control a device from an application designed to work with a COM port.

The Yocto-RS232 follows the TIA/EIA-232-F standard: it communicates by sending a +5.5V/-5.5V signal, and can receive signals up to -25V and +25V. This means that you can't use it to interface directly a chip using a logical serial interface (TTL/CMOS): the signal polarity is usually reversed, and the component is unlikely to support -5.5V. But don't worry, the little brother of the Yocto-RS232 for logical levels is on its way...


In the same way as the Yocto-4-20mA-Rx opened the door to a world of analogic industrial sensors, the Yocto-RS232 will eventually let you work comfortably with many all appliances using RS232, and forget once for all your kamikaze driver nightmare and other phantom serial adapters...

1 - ultrasonix Friday,february 06,2015 13H03

Hey guys i have a large number of ModBus over RS485 can your RS232 device use a signal converter to 485 or not at all compatible

will there be a RS485 RTU ModBus version



2 - mvuilleu (Yocto-Team)Friday,february 06,2015 13H49

@ultrasonix: The Yocto-RS485 will be coming soon, we already have working prototypes :-)

Yoctopuce, get your stuff connected.