A current project I'm working on has run into a bit of a wall. Currently using an Atmega324PB to to service 16 encoders using PCINT (the chip has PCINT on just about all the pins) and the code works well. However, what is needed is a board with 64 inputs with PCINT. My original design had 2 x AVR's but it's not really practical. (ran out of pins). I don't want to go down the expander route if at all possible and polling the inputs isn't going to cut it.
So..... Any chip suggestions? Someone has suggested going down the ARM route, but that sounds like a whole new learning experience.