The second board we built over the weekend was the MiniPiio_ULN2803. From its name you can guess it’s a printed circuit board with a ULN2803 8-channel Darlington driver. The ULN2803 allows us to drive cicuits with significantly higher current (up to mA) then we could with just the Raspberry Pi GPIO pins alone. The GPIO Pins are connected to ULN2803 inputs, with the its outputs going to an array of strip headers laid out as servo pins.
The board design was done in Design Spark PCB and a PDF for the schematics is here.