mowcius - your wish is my command. Here is the updated documentation on the input interface:
http://www.roguerobotics.com/wikidocs/rmp3/documentation/input_interface
Oooh, I do feel powerful 
I presume it is still on the list but what do all the other pads do? From the looks of it, some could be for an FTDI header?
You could introduce a DC offset, but that will require extra components which I think mowcius is trying to avoid.
Aye, I will look into it with as few components as I can get away with though
Mowcius