i2c is a commonly used data bus for communicating between external sensors or other microprocessors. i2c supports up to 127 devices on the bus and so can vastly expand the sensing, processing, and storage capabilities of your Cerebellum. Two i2c ports are placed at right angles to allow easy daisy chaining of the i2c bus. The i2c bus requires a certain line impedance to be set for proper operation; see the jumper reference section for information on setting the i2c line impedance.