I was a professional software developer for thirty years. I can’t think of a single reason that an ice cream machine needs a microcontroller. It’s overkill. It doesn’t do anything more complicated that couldn’t be done with a 555 timer and a bit of TTL logic — even if you wanted it to send a 5V signal somewhere that it needs more ice cream. Are they networked for some stupid reason?
Silly me — I thought 555 meant “read, write” all the way across. (I’ve been off UNIX for a while...666 was read, write, execute all the way across.)
doesn’t do anything more complicated that couldn’t be done with a LOTS OF 555 timers and a MANY TTL logic circuits.