Quote:

However, the ideal way to do it (and save $99) would be to find a single GPIO input pin that the app could read. The app would listen for the pulses and count them to determine the buttons pressed. Any suggestions as to what gpio to use? (e.g one that I can read from user space)


There are several GPIO lines attached to the rear-panel DB-9 connector (serial port). The "headlight sense" line is a good candidate, as it is not normally used for anything when operating on AC power.

That's serial port pin-8 (CTS).
Also possible, is the telephone mute input, on serial port pin-1 (CD).

Cheers