Sure, there is already the KiCAD file including everything to play around with on your own; added a picture of the schematic here for a quick glance without downloading.

thanks for you reply Fumée Bleue.

Here the picture of the assembled board. The top board is a temperature sensor so not necessarily needed.

Please provide the required documentation for the CERN license. See here if anything is unclear.

This is great, thanks! One suggestion: add a switch mode regulator that can handle 12 or 24 volt DC input. This will allow small sensor devices to hang off a typical bus network having extra pairs for the central power supply.

The RPI becomes an ethernet gateway.

There are also other solutions that have I2C bus pins on the shield and if you are going to make a battery powered node, I'd suggest to use an I2C sensor as it will be much more battery friendly

I see a lot of "!TSF" and "NACK" which seems to be radio communication problems. That's MySensors related and can be related to many things, from soldering problem to power / capacitor issues. In MY_DEBUG mode you should see your temp/hum printed on serial every ~15s so there is something wrong there, either wiring or a code issue. Ty with the example included with the library "i2c_SI7021.h", without any MySensors related stuff, to see if your sensor is detected. You should see temp/hum on the serial.

Thank you both for your answers. With so many parameters to play with, it was not easy to understand what was wrong.. But I think I finally got a way do get my hardware working Here are my findings : I thought I got RFM73 version of NRF24-like radios. They look like like here and here. After checking and connecting all VCC and GND together, switch radios and arduinos... I got them suddenly working with Mysensors development librairies, then back to silence without apparent reason... Indeed like @mark_venn suggested, I went back to stable librairies and try so set a static ID. Worked well... until it went back to silence again ! Then, following @mfalkvidd advice, I realised that flashing the eeprom_clear sketch solved my all my problems ! My summary : Ensure that your 3.3V power supply is strong enough. Ensure that your arduino, radios and sensors are sharing the same GND and VCC. Use development librairies from github Flash eeprom_clear before flashing your mysensor sketches Then gatewaySerial and relayActuator should be able to communicate "out of box", mean you'll monitor some lines like this on the gateway serial : 0;255;3;0;9;read: 0-0-0 s=255,c=3,t=15,pt=0,l=2,sg=0: Thanks again for your help, now I can start to play