This kit includes a round printed circuit board (PCB) with holes spaced on a 0.100" grid, two extended 2×7 male headers, two extended 1×2 male headers, one 2×7 female header, two 1×2 female headers, four 7/8" nylon spacers, four 1-1/4" screws, and four nuts.
The expansion PCB matches the 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 LCD pins, ISP programming pins, and 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.