I'm planning to build a 32 relay IOT node next to my Raspberry Pi. The relays will be controlled by an Arduino Mega 2560. The Pi will run Home Assistant and Mosquitto so I would prefer to communicate with the arduino using MQTT. The Arduino and the Pi will be next to each other, the simplest connection would be over serial. I have found a library: https://github.com/vortex314/serial2mqtt it looks not easy to set up. Do you have any other ideas? Thank you!
As the author of the serial2mqtt gateway. Maybe it's time to have a new look. I've included the binaries for different platforms in the build : https://github.com/vortex314/serial2mqtt/tree/master/build So to get started : unzip the binary and update the serial2mqtt.json config. Should be piece of cake. Let me know otherwise via github.
Finally I have found the solution! Using mysensors (mysensors.org) I can use the Arduino Mega as a node and a serial gateway. So Home Assistant can control it directly.