1.GY-26 is a low-cost flat digital compass module. Input voltage and power consumption is   low, small size. Its working  principle is by two mutually perpendicular magnetic sensors response the magnetic component of earth’s magnetic field induction,To arrive at the azimuth angle.

2.This compass to RS232 protocol, and the IIC protocol with other devices. High precision,high stability. And with a re-calibration function, can be in any position accurate azimuth, the output of the baud rate is 9600bps, a continuous output and exercise    output in two ways, with the magnetic declination compensation, can adapt to different working environment.