I will use a series of stm32s (about 3 )to control relays (for lights etc), read sensors (24ghz human presence, pir, current) etc. and send them over to a ‘master’ node over spi with cat6a cables, the master stm32 will respond to the switches etc and send/receive the collective data to the home assistant server. I started learning about mqtt and ha recently but wanted to know if this idea is remotely possible or reliable . (or safe) before going ham on this project. i will be using cheap stm32f10 for the slave node and a stm32f4 for the master .
thanks for reading through this and sorry