Trouble with 115200 baud on 3.3V/8MHz Arduino, like Serial Gateway. Solution: Change baudrate.

[Stric]

Please read http://forum.arduino.cc/index.php?topic=54623.0 which basically says that the 3.3v arduino can't read stuff at 115200 baud correctly, things get corrupted due to being unable to get the correct timings. In our tests, semicolon (;) gets corrupted quite often. Unfortunately, the semicolon is "quite useful" in the serial protocol of the Gateway.

Symptoms: Gateway not responding to version checks, gateway not being able to pass on auto-allocated ID's etc.

Solution: Either change clock to 12MHz (hardware mod + software + blah), or just go slower.. 19200 baud seems to work fine for us. Change baud rate in MySensors.h and recompile your serial gateway. Easy-peasy.

[hek]

@Stric said:

http://forum.arduino.cc/index.php?topic=54623.0

Thanks for posting.

[RJ_Make]

@Stric That is strange, I've never seen this problem, and I have more 3v3 sensors then 5v... Hmmmmmm

[Dirk_H]

@ServiceXP @Stric
I can confirm the problems of Stric. I also had them some months ago. see here http://forum.mysensors.org/topic/824/mysensors-serial-gateway-minimal-example-to-send-data/6

[RJ_Make]

@Dirk_H Oh I believe the problem exists, I'm just wondering why I've not seen it yet....

[hek]

@ServiceXL
It is only a problem if you're using an 3v3 arduino on gateway.

The sensors don't send more than debug info over serial where the problem easily go unnoticed I guess.

[marceltrapman]

Does this mean that the 'early days requirement' of a UNO or Nano for the gateway could be replaced with 'any 5v Arduino' like a pro mini 5v?

[hek]

Yes, unless you run Vera which requires Nano (for usb compatibility).

[Dirk_H]

@marceltrapman
when you change the BAUD rate setting in the source/config file to something lower/other you can also use 3.3V Arduinos as (Serial)Gateway. Of cause your controller needs also to be told about the lower BAUD rate.

Check out http://wormfood.net/avrbaudcalc.php?postbitrate=9600&postclock=8 for an overview of Clockspeeds (usually 8MHz for 3.3V and 16MHz for 5V types) and coresponding BAUD rates.