In the paper, the digital compass based on AVR microcontroller has been developed using MEMS accelerometer-magnetometer LSM303DLHC. The structure and hardware of the digital compass have been developed. The calibration algorithms of the accelerometer and magnetometer of the LSM303DLHC module have been described. The calculation algorithm of the pitch and roll angles has been described. The heading calculation algorithm of the digital compass without tilt compensation and with tilt compensation has been described.
The paper considers the problem of interpreting the Allan deviation plot for signals from sensors polled more frequently than data are refreshed. The Allan variance is a standard tool for analysis of noise terms inevitably present in signals of inertial sensors. There exists a well-defined algorithm for its calculation both for time domain and frequency domain. Having calculated the Allan variance as a function of time (or frequency) one fetches its square root, called Allan deviation, and builds its plot in a logarithmic format.