Data Sheet

Sensor Documentation Modern Robotics, Inc.
Version 1.4.3 16
During normal operation, the LED will blink briefly at 1Hz. During Hard Iron Calibration,
the LED will blink at ½Hz. During tilt up and tilt down calibration the LED will be on
during a period of calibration measurement.
Hard Iron Calibration:
Hard Iron Calibration is entered by setting the command location to 0x43. Once Hard
Iron Calibration is active rotate the Compass 360°, making sure it does not tilt, for a
period of 5 seconds. Once the rotation procedure is complete, the command location
must be set to 0x00 to signal that calibration is complete. If the data collected during
the rotation was good, the Compass will enter Normal Measurement Mode using the
new calibration data. If the data collected during the rotation was not good, the
command value will change to 0x46 and the Compass will enter Normal Measurement
Mode using the previous calibration data.
Tilt Compensation:
Tilt compensation is performed in two steps, tilt up and tilt down in that order.
The first step is tilt up. To set the Compass up for tilt up measurement, the Compass
should be pointed due North and set with the front of the device tiled up by
approximately 20°. Then the command location should be set to 0x55 while the
Compass is held perfectly still. Once the LED extinguishes itself, the command location
will return to 0x00, indicating that tilt up data has been captured.
The second step is tilt down. To set the Compass up for tilt down measurement, the
Compass should be pointed due North and set with the front of the device tilted down
by approximately 20°. Then the command location should be set to 0x44 while the
compass is held perfectly still. Once the LED extinguishes itself, the command location
will return 0x00, indicating that tilt down data has been captured and the tilt
compensation coefficient has been acquired.
If the two tilt steps are not performed in the correct order, or some other error is
detected, the command location will be set to 0x46 and the Compass will enter Normal
Measurement Mode using the previous tilt compensation coefficient.
Accelerometer Nulling:
Accelerometer axis nulling is performed using the three axis null commands. For both
the x and y axis nulling should be performed with the device set perfectly level. Setting
the command location to 0x58 will update the accelerometer X axis offset. Setting the
command location to 0x59 will update the accelerometer Y axis offset. For the Z axis
nulling, the device should be set to be perfectly vertical. Setting the command location
to 0x5A will update the accelerometer Z axis offset