For a year, we have been offering the YoctoHub-Wireless to enable you to connect your Yoctopuce modules directly to a wireless network, without a computer. Experience showed a few limitations of this first version and we are happy to present today its successor: the YoctoHub-Wireless-g. Although nothing changes in its shape or in its use, some people will rejoice. So let's see the improvements...
Our first YoctoHub-Wireless used the 802.11b standard, with a 2Mbits/s maximum. To read sensors and drive actuators, quality of the radio link is indeed more important than speed, as there is not much data to transmit.
However, we discovered after a few months that some Wifi routers contain a serious bug in their management of 802.11b clients: DHCP packets (used to distribute IP addresses) are sent with the 802.11g standard, even to 802.11b clients. As a consequence, DHCP address assignment does simply not work for 802.11b clients. A pity. The only remaining solution is to use a static IP address.
The new YoctoHub-Wireless-g
With the new YoctoHub-Wireless-g, you won't encounter this issue anymore as this new version works with the 802.11g standard (as indicated by its name). With 802.11g, we also gain some transfer speed, in particular to access the module web interface and to send callback connections. In practice, it's about 3-4 times faster when reception is good.
Use without Wifi access point
We wrote several posts on applications where it was interesting to use a YoctoHub-Wireless without a Wifi router. These are typically scenarios where you want to drive an automatic device or retrieve data in the wilderness, from a smart phone.
To do so, you can set up the YoctoHub-Wireless for it to generate a network in "Ad-hoc" mode. This works pretty well... except with Android phones (and tablets). Indeed, for some mysterious reason, Ad-hoc network support was never implemented in Android. This certainly reduced the interest in the above mentioned scenarios.
Fortunately, the new YoctoHub-Wireless-g provides a solution: the virtual access point mode (officially called SoftAP in the standard). This function enables the YoctoHub-Wireless-g to create a Wifi network in the same manner as a classical Wifi access point, which can thus be used by any standard Wifi client, including Android phones and tablets.
There are just two (not very serious) limitations. First, the number of clients connected at the same time is limited to four. Second, obviously this pseudo network doesn't offer Internet access. This disqualifies it for tablets requiring an Internet connection (such as Kindle for example).
Automatic adaptation of transfer speed
A key requirement for us to support 802.11g was to be able to keep the same link quality as with our previous version, even in difficult conditions (great distance). We have been able to verify that, with the YoctoHub-Wireless-g, thanks to the automatic adaptation of transfer speed according to reception quality, you can effectively have serviceable connections more than 300m away in line of sight. At such distances, transfer speed goes down at the same level as for the 802.11b version (and negotiation even takes a little longer because of the delay to fallback to the slow speed), but the link is as it should.
How to recognize it?
Nothing looks more like a YoctoHub-Wireless than another kind of YoctoHub-Wireless: they use the exact same PCB, with the same YoctoHub-Wireless marking regardless of the variant name (ST or 802.11g). The difference is only in the WiFi interface and in the specific YoctoHub-Wireless firmware. So here is the trick to recognize a YoctoHub-Wireless-g at a glance: the PCB of the WiFi interface (next to the antenna connector) is blue, whereas on the 802.11b version it is green.
A YoctoHub-Wireless and a YoctoHub-Wireless-g
Tu wrap up, here is a table summarizing the differences between the various kinds of YoctoHub-Wireless:
Here you are, you know everything. We hope that you enjoy this new version even more than the preceding one...