Generally pedalboards range in size from 13 notes to 32 notes on church or concert organs. Modern pipe organs typically have 30-note or 32-note pedalboards, while some electronic organs and many older pipe organs have 25-note pedalboards.
MIDI keyboards come in a range of sizes, from 25 keys (two octaves) to full 88-key length.
The MIDI IN/OUT board can be used with any microcontroller which contains a UART, including the PIC, ATmega etc. microntrollers, to send and receive MIDI messages.