I’ve been working sporadically on this tiny MIDI controller. It targets the smallest PIC microcontroller available with onboard A/D converter – the PIC10F220.
Currently it reads two potentiometers and a button input using three of the GPIO pins, and it bitbangs the remaining output pin to produce MIDI-Out at 31250hz using cycle-counted delays. Since practically everything is already on-chip, this thing could just be epoxied straight to the enclosure. There are only two or three more components – no PCB required!
This microcontroller sports a whopping 256 instructions and 16 bytes of RAM. Even so, the MIDI controller code consumes less than half the available resources after a modest amount of optimization for size. One might see this as my response to using a certain 32k ROM / 2k RAM microcontroller to blink some lights, but I won’t admit to being that petty.