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/**
* @file FusionOffset.c
* @author Seb Madgwick
* @brief Gyroscope offset correction algorithm for run-time calibration of the
* gyroscope offset.
*/
//------------------------------------------------------------------------------
// Includes
#include "FusionOffset.h"
#include <math.h> // fabsf
//------------------------------------------------------------------------------
// Definitions
/**
* @brief Cutoff frequency in Hz.
*/
#define CUTOFF_FREQUENCY (0.02f)
/**
* @brief Timeout in seconds.
*/
#define TIMEOUT (5)
/**
* @brief Threshold in degrees per second.
*/
#define THRESHOLD (3.0f)
//------------------------------------------------------------------------------
// Functions
/**
* @brief Initialises the gyroscope offset algorithm.
* @param offset Gyroscope offset algorithm structure.
* @param sampleRate Sample rate in Hz.
*/
void FusionOffsetInitialise(FusionOffset *const offset, const unsigned int sampleRate) {
offset->filterCoefficient = 2.0f * (float) M_PI * CUTOFF_FREQUENCY * (1.0f / (float) sampleRate);
offset->timeout = TIMEOUT * sampleRate;
offset->timer = 0;
offset->gyroscopeOffset = FUSION_VECTOR_ZERO;
}
/**
* @brief Updates the gyroscope offset algorithm and returns the corrected
* gyroscope measurement.
* @param offset Gyroscope offset algorithm structure.
* @param gyroscope Gyroscope measurement in degrees per second.
* @return Corrected gyroscope measurement in degrees per second.
*/
FusionVector FusionOffsetUpdate(FusionOffset *const offset, FusionVector gyroscope) {
// Subtract offset from gyroscope measurement
gyroscope = FusionVectorSubtract(gyroscope, offset->gyroscopeOffset);
// Reset timer if gyroscope not stationary
if ((fabsf(gyroscope.axis.x) > THRESHOLD) || (fabsf(gyroscope.axis.y) > THRESHOLD) || (fabsf(gyroscope.axis.z) > THRESHOLD)) {
offset->timer = 0;
return gyroscope;
}
// Increment timer while gyroscope stationary
if (offset->timer < offset->timeout) {
offset->timer++;
return gyroscope;
}
// Adjust offset if timer has elapsed
offset->gyroscopeOffset = FusionVectorAdd(offset->gyroscopeOffset, FusionVectorMultiplyScalar(gyroscope, offset->filterCoefficient));
return gyroscope;
}
//------------------------------------------------------------------------------
// End of file
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