[hello]

I took some old controllers apart and noticed they
had schmidt triggers for signals going into and leaving the processor
They would square the wave up going in?
and
protect the processor as well as add current going out?

have a good day!

[JHolland]

Older processors didn't always have schmitt trigger inputs, the ATMega2560 does and I think STM32 has as well - its a while since I looked at it. You shouldn't need them going out because the rise times are quite high anyway, I expect they were more for buffering. Generally speaking fast edges should be avoided whenever possible because they cause EMC issues.