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"ADXL345 Calibration Technique"

This is the calibration technique I used in my digital bulls eye development project. It involves using an ADXL345 accelerometer for inclination sensing. The calibration technique described involves a 2 point line fit to determine the slope (gain) and offset for each of the 3 axis. Precise leveling from a reference source is paramount for final precision. See the application note for more details. http://www.analog.com/media/en/techni... Here is part one.    • "A LCD Digital Bulls Eye Level w/ADXL345"   C code excerpt from my source.... #define ADXL345_X_GAIN 333 // GAIN factors #define ADXL345_Y_GAIN 326 #define ADXL345_Z_GAIN 268 // read the three registers and pack and cast to signed integers readAccelG(); accX = (float64_t)raw_accX; accY = (float64_t)raw_accY; accZ = (float64_t)raw_accZ; // apply the slope and offset factors accX = ( accX - (-129) ) / ADXL345_X_GAIN; accY = ( accY - (-79) ) / ADXL345_Y_GAIN; accZ = ( accZ - 684 ) / ADXL345_Z_GAIN; pitch = (atan2(accX,sqrt(accY*accY+accZ*accZ)) * 180.0) / PI; roll = (atan2(accY,(sqrt(accX*accX+accZ*accZ))) * 180.0) / PI;