Let the coding commence!
With the motor controller wired up and (mostly) working its time to start on the software, as without that the robot isn't going to be moving far, and to allow you to follow on with development I've created a new Git repository at https://github.com/LeoWhite/OptimusPi
|The motor driver haphazardly connected to the chassis.|
To being with I've just taken some of the source code I used last year (The Arduino source and a cut down python test script), cut out the unused functionality and updated it to support the 'Monster Moto Shield' instead of the T'Rex controller. With a bit of fiddling I'm now able to drive the motors using a PS3 controller.
Obviously this is just an initial test and its going to take a lot more work to get the robot driving around autonomously (I can already see the watchdog firing on the Arduino.. an issue I had last year too), but its a good starting point!