The board uses an I2C I/O expander to support the two motor drivers as well as 4 freely available I/O pins.

The motor drivers are based on the TC4424 chip, which is mainly intended for driving MOSFET chips, but which happens to also work well to drive small motors forward or backward. Motors with stall currents up to about 1.5A @ 4.5..18V should work just fine.

An I2C bus running at 3.3V is used for I/O, with all the power and signal lines brought out to to both sides of the board to allow daisy-chaining with other I2C-conformant boards.