@ben999
Check out Serial Protocol
I have four Arduinos. Each has a different MY_NODE_IDs (I use 130, 131, 132, 133). Each has four sensors: moisture, humidity, temperature, and voltage each of which has a CHILD_ID: CHILD_ID_MOISTURE is 0 , CHILD_ID_HUMIDITY is 1, CHILD_ID_TEMPERATURE is 2, CHILD_ID_VOLTAGE is 3.
When an Arduino makes a measurement, it sends that measurement to a unique MQTT topic. In the case of the Arduino with MY_NODE_ID of 130 that is sending the moisture measurement, that MQTT topic is mysensors_out/130/0/1/0/35 and the message is [something like] 760 (35 is the value type)
Similarly, when a controller sends a command to a device (Arduino), the topic is unique.
If you have two actuators with the same MY_NODE_ID and CHILD_ID (MQTT topic) there would be confusion as to what you want each actuator to do. Likewise, if two sensors had the same MQTT topic, how would the controller know how to handle the data.
Replying myself after more reading and testing.
*MQTT vs ETH probably is equivalent in my system, if the choice if given I think MQTT is preferred.
*NRF24 or RFM69, maybe both as I already have a bunch of NRF24 radios home and can start build directly.
*PC based MQTT could be an idea, but probably its as easy to work through an Arduino-example using the serial monitor in an Arduino-environment.
My way forward will be:
Remove the RPi-GPIO-gateway (I built a basic node and tested it, but could not communicate with the GW) and replace it with ESP8266-based WIFI/MQTT/Radio-gateway (one with NRF24 and eventually one with RFM69).
I believe that will be an easier way into mySensors-world also limiting the amount of required Linux-related knowledge. It will be easier to debug the system from Arduino IDE-serial console. Ie start and confirm OH3 to MySensors-MQTT-gateway, then proceeding with sensor to gateway communication etc.
