ManyMIDIprojects end up with several input buttons and knobs. What if you need more inputs to control on your musical device? This is where Chomp (Configurable Hardware Open-Source MIDI Platform) may be useful. It is capable of reading 48 analog and digital signals and outputMIDI.
It is based on ATmega328 microcontroller so the software is written in arduino way – no problem if you want to modify it. Inputs are organized in to several 2×5 ribbon cable connectors, so no problem to attach your custom button boards or integrate in to your projects.