Here's the schematic and source code for a MIDI footswitch controller.
My original schematic was lost in the transition from Mac to PC about
three years ago. It is a simple circuit, so tracing it out with a DMM
was easy.

Here's what it does:

uses a PIC16C54 running at 4Mhz
scans a 3 x 4 switch matrix (0 through 9, bank up and bank down)
drives a multiplexed 2 1/2 digit display
selectable midi channel via 4-position dip switch
selectable display range via SPST switch or jumper (0 to 127 or 1 to
128)

The code is not optimized, nor is it elegant, but it does work.

http://www.geocities.com/SiliconValley/Haven/9004/

Enjoy.

Dave