Hacking an Invacare Pronto Electric Wheelchair - Part 2

The joystick on the wheelchair turned out to be connected with a 6-wire cable and probing the signals on that cable with my oscilliscope turned up something that looked a lot like a 9600bps serial data feed. After a few hours of analysing the data flow from the joystick (and a lucky pdf find) I managed to send the right data to get the PC recognised as a 'System Attendant' secondary (overriding) joystick.