This kit gives you everything you need to add a second level to your 3pi robot. The black printed circuit board matches the color of the 3pi and has cutouts that let you view the LCD below and make it easier to reach the power button, reset button, and programming header.

The expansion PCB matches diameter of the 3pi chassis and mounts just above the tops of the wheels using the four included screws and spacers. Once assembled, the PCB has electrical connections to the base that allow you interface your own electronics with the 3pi robot, which is sold separately. These connections give you access to the ATmega168’s free/jumpered pins, as well as to the three on-board voltages: VBAT (battery voltage), VCC (regulated 5 V), and VBST (regulated 9.25 V that is supplied to the motors). Additionally, the expansion PCB connects to the base’s power button and battery charge port, allowing you to add your own power buttons and charge ports.