Yeah I found the thread with this particular code as well. Just didnt have the time to fully understand it. However, I do get the concept now and that is most important to me. Still, right now, it doesnt make sense to me to dig deeper into it, because I just gain MQTT discovery by it. Given the amount of work I would have to put into fully understanding it, it’s not worth it for me right now. Will get back to it at a later point though for sure. 
Hello, I’m using an Arduino Mega to control a lot of thing, I have a 16 relay board, some switches and somes weather analog devices. I would like to use the MQTT addon with the entities auto-discovering.
I search on google to find how to configure my Arduino board to be discovered without succes (I only found Tasmota things).
If you can give me some hints to how to do it I really appreciate. Actually my Arduino communicate with HASS, I see it on the Developper MQTT page but my Entities are not discovered and add to the integration.
Thanks!