Make:it shield questions

I have the make:it robot starter kit. And i want to do some customizing of the robot by adding more sensors and motors. However the shield that came with the kit has no schematic and i cant find anything on the internet about how this shield works. I see that it has two h-bridge ics on it to control 4 motors and i see where the ir sensors plug in at. but my question is what if i want to add a sonic sensor or other devices to this board, how am i suppose to figure out what all the other connections are for?

This may help.


Everything you need for the Make:it robot is on line at GitHub.