Pixhawk / APM flight control only one I2C interface, the situation To connect over multiple I2C peripherals, you can use this breakout board; Pixhawk-I2C Breakout Board with five completely parallel vertical 1.25-4 bit socket convenient in 1 trailer 4 is connected four I2C peripherals such situation while using an external compass module with RGB or hope the case of connecting a plurality of RGB modules