Here is an early run of my tablebot. The link: Dexter, the tablebot
It’s a RaspberryPi B+ with the BrickPi board and a PiTFT on the side. That works because the BrickPi talks Serial and the PiTFT talks SPI;-) So they can both coexist on the same connector.
The bot has eight Pololu QTR-L-1RC sensors to detect the edges of the table and react to it. They are connected to a Arduino Micro on the very top that talks via USB to the Pi. The detection still needs some work;-)
The BrickPi is running some custom firmware. I hope to clean that up some more, but it lives @ github if somebody is curious. Basically, it’s using a completely different protocol to control the motors.
The robot is powered by a RC LiPo 7.2V 2200mAh battery. I found that those work much better than AA’s (and even the NiMH AA’s) with most Lego NXT & power function projects. Also, the battery has the little equalizing/slow charging connecter which sticks out in the back, so I can charge it in place;-)