File content as of revision 1:c3381056a1c6:

/***************************************************************************
  This is a library for the Adafruit 9DOF Breakout

  Designed specifically to work with the Adafruit 9DOF Breakout:
  http://www.adafruit.com/products/1714

  These displays use I2C to communicate, 2 pins are required to interface.

  Adafruit invests time and resources providing this open source code,
  please support Adafruit andopen-source hardware by purchasing products
  from Adafruit!

  Written by Kevin Townsend for Adafruit Industries.  
  BSD license, all text above must be included in any redistribution
 ***************************************************************************/

#include <math.h>
#include "Adafruit_9DOF.h"
#define PI  (3.14159265F);

/***************************************************************************
 PRIVATE FUNCTIONS
 ***************************************************************************/


/***************************************************************************
 CONSTRUCTOR
 ***************************************************************************/
 
/**************************************************************************/
/*!
    @brief  Instantiates a new Adafruit_9DOF class
*/
/**************************************************************************/
Adafruit_9DOF::Adafruit_9DOF(void) 
{
}

/***************************************************************************
 PUBLIC FUNCTIONS
 ***************************************************************************/
 
/**************************************************************************/
/*!
    @brief  Setups the HW
*/
/**************************************************************************/
bool Adafruit_9DOF::begin(){
  // Enable I2C
  return true;
}

/**************************************************************************/
/*!
    @brief  Populates the .pitch/.roll fields in the sensors_vec_t struct
            with the right angular data (in degree)

    @param  event         The sensors_event_t variable containing the
                          data from the accelerometer
    @param  orientation   The sensors_vec_t object that will have it's
                          .pitch and .roll fields populated
    @return Returns true if the operation was successful, false if there
            was an error
            
    @code

    bool error;
    sensors_event_t event;
    sensors_vec_t orientation;
    ...
    lsm303accelGetSensorEvent(&event);
    error = accelGetOrientation(&event, &orientation);

    @endcode
*/
/**************************************************************************/
bool Adafruit_9DOF::accelGetOrientation(sensors_event_t *event, sensors_vec_t *orientation)
{
  /* Make sure the input is valid, not null, etc. */
  if (event == NULL) return false;
  if (orientation == NULL) return false;

  float t_pitch;
  float t_roll;
  float signOfZ = event->acceleration.z >= 0 ? 1.0F : -1.0F;

  /* roll: Rotation around the longitudinal axis (the plane body, 'X axis'). -90<=roll<=90    */
  /* roll is positive and increasing when moving downward                                     */
  /*                                                                                          */
  /*                                 y                                                        */
  /*             roll = atan(-----------------)                                               */
  /*                          sqrt(x^2 + z^2)                                                 */
  /* where:  x, y, z are returned value from accelerometer sensor                             */

  t_roll = event->acceleration.x * event->acceleration.x + event->acceleration.z * event->acceleration.z;
  orientation->roll = (float)atan2(event->acceleration.y, sqrt(t_roll)) * 180 / PI;

  /* pitch: Rotation around the lateral axis (the wing span, 'Y axis'). -180<=pitch<=180)     */
  /* pitch is positive and increasing when moving upwards                                     */
  /*                                                                                          */
  /*                                 x                                                        */
  /*             roll = atan(-----------------)                                               */
  /*                          sqrt(y^2 + z^2)                                                 */
  /* where:  x, y, z are returned value from accelerometer sensor                             */

  t_pitch = event->acceleration.y * event->acceleration.y + event->acceleration.z * event->acceleration.z;
  orientation->pitch = (float)atan2(event->acceleration.x, signOfZ * sqrt(t_pitch)) * 180 / PI;

  return true;
}


/**************************************************************************/
/*!
    @brief  Utilize the sensor data from an accelerometer to compensate
            the magnetic sensor measurements when the sensor is tilted
            (the pitch and roll angles are not equal 0�)

    @param  axis          The given axis (SENSOR_AXIS_X/Y/Z) that is
                          parallel to the gravity of the Earth

    @param  mag_event     The raw magnetometer data to adjust for tilt

    @param  accel_event   The accelerometer event data to use to determine
                          the tilt when compensating the mag_event values

    @code

    // Perform tilt compensation with matching accelerometer data
    sensors_event_t accel_event;
    error = lsm303accelGetSensorEvent(&accel_event);
    if (!error)
    {
      magTiltCompensation(SENSOR_AXIS_Z, &mag_event, &accel_event);
    }

    @endcode
*/
/**************************************************************************/
bool Adafruit_9DOF::magTiltCompensation(sensors_axis_t axis, sensors_event_t *mag_event, sensors_event_t *accel_event)
{
  /* Make sure the input is valid, not null, etc. */
  if (mag_event == NULL) return false;
  if (accel_event == NULL) return false;

  float accel_X, accel_Y, accel_Z;
  float *mag_X, *mag_Y, *mag_Z;

  switch (axis)
  {
    case SENSOR_AXIS_X:
      /* The X-axis is parallel to the gravity */
      accel_X = accel_event->acceleration.y;
      accel_Y = accel_event->acceleration.z;
      accel_Z = accel_event->acceleration.x;
      mag_X = &(mag_event->magnetic.y);
      mag_Y = &(mag_event->magnetic.z);
      mag_Z = &(mag_event->magnetic.x);
      break;

    case SENSOR_AXIS_Y:
      /* The Y-axis is parallel to the gravity */
      accel_X = accel_event->acceleration.z;
      accel_Y = accel_event->acceleration.x;
      accel_Z = accel_event->acceleration.y;
      mag_X = &(mag_event->magnetic.z);
      mag_Y = &(mag_event->magnetic.x);
      mag_Z = &(mag_event->magnetic.y);
      break;

    case SENSOR_AXIS_Z:
      /* The Z-axis is parallel to the gravity */
      accel_X = accel_event->acceleration.x;
      accel_Y = accel_event->acceleration.y;
      accel_Z = accel_event->acceleration.z;
      mag_X = &(mag_event->magnetic.x);
      mag_Y = &(mag_event->magnetic.y);
      mag_Z = &(mag_event->magnetic.z);
      break;

    default:
      return false;
  }

  float t_roll = accel_X * accel_X + accel_Z * accel_Z;
  float rollRadians = (float)atan2(accel_Y, sqrt(t_roll));

  float t_pitch = accel_Y * accel_Y + accel_Z * accel_Z;
  float pitchRadians = (float)atan2(accel_X, sqrt(t_pitch));

  float cosRoll = (float)cos(rollRadians);
  float sinRoll = (float)sin(rollRadians);
  float cosPitch = (float)cos(-1*pitchRadians);
  float sinPitch = (float)sin(-1*pitchRadians);

  /* The tilt compensation algorithm                            */
  /* Xh = X.cosPitch + Z.sinPitch                               */
  /* Yh = X.sinRoll.sinPitch + Y.cosRoll - Z.sinRoll.cosPitch   */
  *mag_X = (*mag_X) * cosPitch + (*mag_Z) * sinPitch;
  *mag_Y = (*mag_X) * sinRoll * sinPitch + (*mag_Y) * cosRoll - (*mag_Z) * sinRoll * cosPitch;

  return true;
}

/**************************************************************************/
/*!
    @brief  Populates the .heading fields in the sensors_vec_t
            struct with the right angular data (0-359�)

            Heading increases when measuring clockwise

    @param  axis          The given axis (SENSOR_AXIS_X/Y/Z)

    @param  event         The raw magnetometer sensor data to use when
                          calculating out heading

    @param  orientation   The sensors_vec_t object where we will
                          assign an 'orientation.heading' value

    @code

    magGetOrientation(SENSOR_AXIS_Z, &mag_event, &orientation);

    @endcode
*/
/**************************************************************************/
bool Adafruit_9DOF::magGetOrientation(sensors_axis_t axis, sensors_event_t *event, sensors_vec_t *orientation)
{
  /* Make sure the input is valid, not null, etc. */
  if (event == NULL) return false;
  if (orientation == NULL) return false;

  switch (axis)
  {
    case SENSOR_AXIS_X:
      /* Sensor rotates around X-axis                                                                 */
      /* "heading" is the angle between the 'Y axis' and magnetic north on the horizontal plane (Oyz) */
      /* heading = atan(Mz / My)                                                                      */
      orientation->heading = (float)atan2(event->magnetic.z, event->magnetic.y) * 180 / PI;
      break;

    case SENSOR_AXIS_Y:
      /* Sensor rotates around Y-axis                                                                 */
      /* "heading" is the angle between the 'Z axis' and magnetic north on the horizontal plane (Ozx) */
      /* heading = atan(Mx / Mz)                                                                      */
      orientation->heading = (float)atan2(event->magnetic.x, event->magnetic.z) * 180 / PI;
      break;

    case SENSOR_AXIS_Z:
      /* Sensor rotates around Z-axis                                                                 */
      /* "heading" is the angle between the 'X axis' and magnetic north on the horizontal plane (Oxy) */
      /* heading = atan(My / Mx)                                                                      */
      orientation->heading = (float)atan2(event->magnetic.y, event->magnetic.x) * 180 / PI;
      break;

    default:
      return false;
  }

  /* Normalize to 0-359� */
  if (orientation->heading < 0)
  {
    orientation->heading = 360 + orientation->heading;
  }

  return true;
}

/**************************************************************************/
/*!
    @brief  Populates the .roll/.pitch/.heading fields in the sensors_vec_t
            struct with the right angular data (in degree).

            The starting position is set by placing the object flat and
            pointing northwards (Z-axis pointing upward and X-axis pointing
            northwards).

            The orientation of the object can be modeled as resulting from
            3 consecutive rotations in turn: heading (Z-axis), pitch (Y-axis),
            and roll (X-axis) applied to the starting position.


    @param  accel_event   The sensors_event_t variable containing the
                          data from the accelerometer

    @param  mag_event     The sensors_event_t variable containing the
                          data from the magnetometer

    @param  orientation   The sensors_vec_t object that will have it's
                          .roll, .pitch and .heading fields populated
*/
/**************************************************************************/
bool Adafruit_9DOF::fusionGetOrientation(sensors_event_t *accel_event, sensors_event_t *mag_event, sensors_vec_t *orientation)
{
  /* Make sure the input is valid, not null, etc. */
  if ( accel_event  == NULL) return false;
  if ( mag_event    == NULL) return false;
  if ( orientation  == NULL) return false;

  float const PI_F = 3.14159265F;

  /* roll: Rotation around the X-axis. -180 <= roll <= 180                                          */
  /* a positive roll angle is defined to be a clockwise rotation about the positive X-axis          */
  /*                                                                                                */
  /*                    y                                                                           */
  /*      roll = atan2(---)                                                                         */
  /*                    z                                                                           */
  /*                                                                                                */
  /* where:  y, z are returned value from accelerometer sensor                                      */
  orientation->roll = (float)atan2(accel_event->acceleration.y, accel_event->acceleration.z);

  /* pitch: Rotation around the Y-axis. -180 <= roll <= 180                                         */
  /* a positive pitch angle is defined to be a clockwise rotation about the positive Y-axis         */
  /*                                                                                                */
  /*                                 -x                                                             */
  /*      pitch = atan(-------------------------------)                                             */
  /*                    y * sin(roll) + z * cos(roll)                                               */
  /*                                                                                                */
  /* where:  x, y, z are returned value from accelerometer sensor                                   */
  if (accel_event->acceleration.y * sin(orientation->roll) + accel_event->acceleration.z * cos(orientation->roll) == 0)
    orientation->pitch = accel_event->acceleration.x > 0 ? (PI_F / 2) : (-PI_F / 2);
  else
    orientation->pitch = (float)atan(-accel_event->acceleration.x / (accel_event->acceleration.y * sin(orientation->roll) + \
                                                                     accel_event->acceleration.z * cos(orientation->roll)));

  /* heading: Rotation around the Z-axis. -180 <= roll <= 180                                       */
  /* a positive heading angle is defined to be a clockwise rotation about the positive Z-axis       */
  /*                                                                                                */
  /*                                       z * sin(roll) - y * cos(roll)                            */
  /*   heading = atan2(--------------------------------------------------------------------------)  */
  /*                    x * cos(pitch) + y * sin(pitch) * sin(roll) + z * sin(pitch) * cos(roll))   */
  /*                                                                                                */
  /* where:  x, y, z are returned value from magnetometer sensor                                    */
  orientation->heading = (float)atan2(mag_event->magnetic.z * sin(orientation->roll) - mag_event->magnetic.y * cos(orientation->roll), \
                                      mag_event->magnetic.x * cos(orientation->pitch) + \
                                      mag_event->magnetic.y * sin(orientation->pitch) * sin(orientation->roll) + \
                                      mag_event->magnetic.z * sin(orientation->pitch) * cos(orientation->roll));


  /* Convert angular data to degree */
  orientation->roll = orientation->roll * 180 / PI_F;
  orientation->pitch = orientation->pitch * 180 / PI_F;
  orientation->heading = orientation->heading * 180 / PI_F;

  return true;
}