I have a very similar pedalboard with a 15-pin D plug, and looking at the interior, it simply connects the switches to most of the pins via diodes. Unfortunately two of the pedals are broken, and although the very helpful makers sent me two spare pedals free of charge, I have to find a way of removing the spindle that they're mounted on. Anyroadup, if you're not scared of soldering, electronics, and programming, you could make a MIDI pedalboard from that (just using it for the switches), a multiplexor or array of diodes to reduce the 13 notes to a 4-bit binary number, and an Arduino.