Guidance
Gyro/Accelerometer Calibration
gyroscope data each time the navX-sensor circuit board is powered on.
Note that the onboard gyroscopes are sensitive to temperature changes. Therefore, since the average
ambient temperature at the factory (on the island of Kauai in Hawaii) may be different than in your
environment, you can optionally choose to re-calibrate the gyroscope by pressing and holding the “CAL”
button for at least 10 seconds. When you release the “CAL” button, ensure that the “CAL” Led flashes
briefly, and then press the “RESET” button to restart navX-sensor. When navX-sensor is re-started, it
will perform the Initial Gyro Calibration – the same process that occurs at our factory. NOTE: It is very
important to hold navX-sensor still, and parallel to the earth’s surface, during this Initial Gyro
Calibration period. You might consider performing this process before using your robot the first time it is
used within a new environment (e.g., when you arrive at a FTC competition event).
The value of re-running Factory Calibration at the same temperature navX-sensor will be operated at is
potentially increased yaw accuracy as well as faster Startup Calibration. If a significant temperature shift
has occurred since the last Factory Calibration, the Startup Calibration time may take longer than normal,
and it’s possible that yaw accuracy will be diminished until the next On-the-fly Gyro Calibration
completes.
“Second Generation” navX-sensor Factory Calibration Time (if still): ~2 seconds
“Classic” navX-sensor Factory Calibration Time (if still): ~15 seconds
Startup Calibration
Startup Calibration occurs each time the navX-sensor is powered on, and requires that the sensor be held
still in order to complete successfully. Using the Factory Calibration as a starting point, the sensor
calibrates the accelerometers and adjusts the gyroscope calibration data as well based upon current
temperature conditions.
If the sensor continues to move during startup calibration, Startup Calibration will eventually timeout –
and as a result, the navX-sensor yaw angle may not be as accurate as expected.
“Second Generation” navX-sensor Startup Calibration Time (if still): ~1 second
“Classic” navX-sensor Startup Calibration Time (if still): ~15 seconds
Initial Yaw Offset Calibration
During Startup Calibration, an Initial Yaw Offset is automatically calculated. The purpose of the Initial
Yaw Offset is to ensure that whatever direction the “front” of the navX-sensor circuit board is pointed to
at startup (after initial calibration is applied) will be considered “0 degrees”.
Yaw Offset Calibration requires that navX-sensor be still during Startup Calibration. After approximately
2 seconds of no motion, the navX-sensor will acquire the current yaw angle, and will subtract it from
future yaw measurements automatically. The navX-sensor protocol and libraries provide a way to
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