After some further review of Atmel’s more advanced versions of the AVR architecture, I came to the conclusion that we’re better off sticking to the ATmega328 used to power the Arduino. It will give us enough I/Os and memory for what we need, and it will allow us to borrow from the extensive collection of open hardware projects built for this platform. As a result, we’ve modified our design to take advantage of this smaller microcontroller.
On this screenshot, you can see how we will use the ATmega328 to drive the motorized fader attached to a bargraph board, three swtiches, and two 64-LED bargraphs. The latter will be controlled by 24 LED drivers, with an extra one for the LEDs of the three switches. Hopefully, the little ATmega328 should be able to handle the load. And if it does not, we’ll upgrade to a more substantial version, but I really doubt that we’ll have to.