File content as of revision 2:fae851819c43:

#ifndef IMU_FILTER_H
#define IMU_FILTER_H

#include "mbed.h"

#define PI 3.1415926536
#define g0 9.812865328//Gravity at Earth's surface in m/s/s
#define SAMPLES 4//Number of samples to average.
#define CALIBRATION_SAMPLES 64//128//Number of samples to be averaged for a null bias calculation//during calibration.
#define toDegrees(x) (x * 57.2957795)//Convert from radians to degrees.
#define toRadians(x) (x * 0.01745329252)//Convert from degrees to radians.
#define GYROSCOPE_GAIN (1 / 14.375)//ITG-3200 sensitivity is 14.375 LSB/(degrees/sec).
#define ACCELEROMETER_GAIN (0.004 * g0)//Full scale resolution on the ADXL345 is 4mg/LSB.
#define GYRO_RATE   0.005//Sampling gyroscope at 200Hz.
#define ACC_RATE    0.005//Sampling accelerometer at 200Hz.
#define FILTER_RATE 0.1//Updating filter at 40Hz.

class IMUfilter {

public:

    /**
     * Constructor.
     *
     * Initializes filter variables.
     *
     * @param rate The rate at which the filter should be updated.
     * @param gyroscopeMeasurementError The error of the gyroscope in degrees
     *  per second. This used to calculate a tuning constant for the filter.
     *  Try changing this value if there are jittery readings, or they change
     *  too much or too fast when rotating the IMU.
     */
    IMUfilter(double rate, double gyroscopeMeasurementError);

    /**
     * Update the filter variables.
     *
     * @param w_x X-axis gyroscope reading in rad/s.
     * @param w_y Y-axis gyroscope reading in rad/s.
     * @param w_z Z-axis gyroscope reading in rad/s.
     * @param a_x X-axis accelerometer reading in m/s/s.
     * @param a_y Y-axis accelerometer reading in m/s/s.
     * @param a_z Z-axis accelerometer reading in m/s/s.
     */
    void updateFilter(double w_x, double w_y, double w_z,
                      double a_x, double a_y, double a_z);

    /**
     * Compute the Euler angles based on the current filter data.
     */
    void computeEuler(void);

    /**
     * Get the current roll.
     *
     * @return The current roll angle in radians.
     */
    double getRoll(void);

    /**
     * Get the current pitch.
     *
     * @return The current pitch angle in radians.
     */
    double getPitch(void);

    /**
     * Get the current yaw.
     *
     * @return The current yaw angle in radians.
     */
    double getYaw(void);

    /**
     * Reset the filter.
     */
    void reset(void);

private:

    int firstUpdate;

    //Quaternion orientation of earth frame relative to auxiliary frame.
    double AEq_1;
    double AEq_2;
    double AEq_3;
    double AEq_4;

    //Estimated orientation quaternion elements with initial conditions.
    double SEq_1;
    double SEq_2;
    double SEq_3;
    double SEq_4;

    //Sampling period
    double deltat;

    //Gyroscope measurement error (in degrees per second).
    double gyroMeasError;

    //Compute beta (filter tuning constant..
    double beta;

    double phi;
    double theta;
    double psi;

};

#endif /* IMU_FILTER_H */