ardupilot/libraries/AP_Compass/AP_Compass_HMC5843.cpp

// -*- tab-width: 4; Mode: C++; c-basic-offset: 3; indent-tabs-mode: t -*-
/*
 *       AP_Compass_HMC5843.cpp - Arduino Library for HMC5843 I2C magnetometer
 *       Code by Jordi Muñoz and Jose Julio. DIYDrones.com
 *
 *       This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *       Sensor is conected to I2C port
 *       Sensor is initialized in Continuos mode (10Hz)
 *
 */

// AVR LibC Includes
#include <math.h>
#include <FastSerial.h>
#if defined(ARDUINO) && ARDUINO >= 100
 #include "Arduino.h"
#else
 #include "WConstants.h"
#endif

#include <I2C.h>
#include "AP_Compass_HMC5843.h"

#define COMPASS_ADDRESS       0x1E
#define ConfigRegA           0x00
#define ConfigRegB           0x01
#define magGain              0x20
#define PositiveBiasConfig   0x11
#define NegativeBiasConfig   0x12
#define NormalOperation      0x10
#define ModeRegister         0x02
#define ContinuousConversion 0x00
#define SingleConversion     0x01

// ConfigRegA valid sample averaging for 5883L
#define SampleAveraging_1    0x00
#define SampleAveraging_2    0x01
#define SampleAveraging_4    0x02
#define SampleAveraging_8    0x03

// ConfigRegA valid data output rates for 5883L
#define DataOutputRate_0_75HZ 0x00
#define DataOutputRate_1_5HZ  0x01
#define DataOutputRate_3HZ    0x02
#define DataOutputRate_7_5HZ  0x03
#define DataOutputRate_15HZ   0x04
#define DataOutputRate_30HZ   0x05
#define DataOutputRate_75HZ   0x06

// read_register - read a register value
bool AP_Compass_HMC5843::read_register(uint8_t address, uint8_t *value)
{
    if (I2c.read((uint8_t)COMPASS_ADDRESS, address, 1, value) != 0) {
        healthy = false;
        return false;
    }
    return true;
}

// write_register - update a register value
bool AP_Compass_HMC5843::write_register(uint8_t address, byte value)
{
    if (I2c.write((uint8_t)COMPASS_ADDRESS, address, value) != 0) {
        healthy = false;
        return false;
    }
    return true;
}

// Read Sensor data
bool AP_Compass_HMC5843::read_raw()
{
    uint8_t buff[6];

    if (I2c.read(COMPASS_ADDRESS, 0x03, 6, buff) != 0) {
        healthy = false;
        return false;
    }

    int16_t rx, ry, rz;
    rx = (int16_t)(buff[0] << 8) | buff[1];
    if (product_id == AP_COMPASS_TYPE_HMC5883L) {
        rz = (int16_t)(buff[2] << 8) | buff[3];
        ry = (int16_t)(buff[4] << 8) | buff[5];
    } else {
        ry = (int16_t)(buff[2] << 8) | buff[3];
        rz = (int16_t)(buff[4] << 8) | buff[5];
    }
    if (rx == -4096 || ry == -4096 || rz == -4096) {
        // no valid data available
        return false;
    }

    _mag_x = -rx;
    _mag_y =  ry;
    _mag_z = -rz;

    return true;
}


// accumulate a reading from the magnetometer
void AP_Compass_HMC5843::accumulate(void)
{
   uint32_t tnow = micros();
   if (healthy && _accum_count != 0 && (tnow - _last_accum_time) < 13333) {
	  // the compass gets new data at 75Hz
	  return;
   }
   if (read_raw()) {
	  // the _mag_N values are in the range -2048 to 2047, so we can
	  // accumulate up to 15 of them in an int16_t. Let's make it 14
	  // for ease of calculation. We expect to do reads at 10Hz, and
	  // we get new data at most 75Hz, so we don't expect to
	  // accumulate more than 8 before a read
	  _mag_x_accum += _mag_x;
	  _mag_y_accum += _mag_y;
	  _mag_z_accum += _mag_z;
	  _accum_count++;
	  if (_accum_count == 14) {
		 _mag_x_accum /= 2;
		 _mag_y_accum /= 2;
		 _mag_z_accum /= 2;
		 _accum_count = 7;
	  }
	  _last_accum_time = tnow;
   }
}


/*
 *  re-initialise after a IO error
 */
bool AP_Compass_HMC5843::re_initialise()
{
    if (!write_register(ConfigRegA, _base_config) ||
        !write_register(ConfigRegB, magGain) ||
        !write_register(ModeRegister, ContinuousConversion))
        return false;
    return true;
}


// Public Methods //////////////////////////////////////////////////////////////
bool
AP_Compass_HMC5843::init()
{
    int numAttempts = 0, good_count = 0;
    bool success = false;
    byte calibration_gain = 0x20;
    uint16_t expected_x = 715;
    uint16_t expected_yz = 715;
    float gain_multiple = 1.0;

    delay(10);

    // determine if we are using 5843 or 5883L
    if (!write_register(ConfigRegA, SampleAveraging_8<<5 | DataOutputRate_75HZ<<2 | NormalOperation) ||
        !read_register(ConfigRegA, &_base_config)) {
        healthy = false;
        return false;
    }
    if ( _base_config == (SampleAveraging_8<<5 | DataOutputRate_75HZ<<2 | NormalOperation)) {
        // a 5883L supports the sample averaging config
        product_id = AP_COMPASS_TYPE_HMC5883L;
        calibration_gain = 0x60;
        expected_x = 766;
        expected_yz  = 713;
        gain_multiple = 660.0 / 1090;  // adjustment for runtime vs calibration gain
    } else if (_base_config == (NormalOperation | DataOutputRate_75HZ<<2)) {
        product_id = AP_COMPASS_TYPE_HMC5843;
    } else {
        // not behaving like either supported compass type
        return false;
    }

    calibration[0] = 0;
    calibration[1] = 0;
    calibration[2] = 0;

    while ( success == 0 && numAttempts < 20 && good_count < 5)
    {
        // record number of attempts at initialisation
        numAttempts++;

        // force positiveBias (compass should return 715 for all channels)
        if (!write_register(ConfigRegA, PositiveBiasConfig))
            continue;      // compass not responding on the bus
        delay(50);

        // set gains
        if (!write_register(ConfigRegB, calibration_gain) ||
            !write_register(ModeRegister, SingleConversion))
            continue;

        // read values from the compass
        delay(50);
        if (!read_raw())
            continue;      // we didn't read valid values

        delay(10);

        float cal[3];

        cal[0] = fabs(expected_x / (float)_mag_x);
        cal[1] = fabs(expected_yz / (float)_mag_y);
        cal[2] = fabs(expected_yz / (float)_mag_z);

        if (cal[0] > 0.7 && cal[0] < 1.3 &&
            cal[1] > 0.7 && cal[1] < 1.3 &&
            cal[2] > 0.7 && cal[2] < 1.3) {
            good_count++;
            calibration[0] += cal[0];
            calibration[1] += cal[1];
            calibration[2] += cal[2];
        }

#if 0
        /* useful for debugging */
        Serial.print("mag_x: ");
        Serial.print(_mag_x);
        Serial.print(" mag_y: ");
        Serial.print(_mag_y);
        Serial.print(" mag_z: ");
        Serial.println(_mag_z);
        Serial.print("CalX: ");
        Serial.print(calibration[0]/good_count);
        Serial.print(" CalY: ");
        Serial.print(calibration[1]/good_count);
        Serial.print(" CalZ: ");
        Serial.println(calibration[2]/good_count);
#endif
    }

    if (good_count >= 5) {
        calibration[0] = calibration[0] * gain_multiple / good_count;
        calibration[1] = calibration[1] * gain_multiple / good_count;
        calibration[2] = calibration[2] * gain_multiple / good_count;
        success = true;
    } else {
        /* best guess */
        calibration[0] = 1.0;
        calibration[1] = 1.0;
        calibration[2] = 1.0;
    }

    // leave test mode
    if (!re_initialise()) {
        return false;
    }

    _initialised = true;

	// perform an initial read
	healthy = true;
	read();

    return success;
}

// Read Sensor data
bool AP_Compass_HMC5843::read()
{
    if (!_initialised) {
        // someone has tried to enable a compass for the first time
        // mid-flight .... we can't do that yet (especially as we won't
        // have the right orientation!)
        return false;
    }
    if (!healthy) {
        if (millis() < _retry_time) {
            return false;
        }
        if (!re_initialise()) {
            _retry_time = millis() + 1000;
            return false;
        }
    }

	if (_accum_count == 0) {
	   accumulate();
	   if (!healthy || _accum_count == 0) {
		  // try again in 1 second, and set I2c clock speed slower
		  _retry_time = millis() + 1000;
		  I2c.setSpeed(false);
		  return false;
	   }
	}

	mag_x = _mag_x_accum * calibration[0] / _accum_count;
	mag_y = _mag_y_accum * calibration[1] / _accum_count;
	mag_z = _mag_z_accum * calibration[2] / _accum_count;
	_accum_count = 0;
	_mag_x_accum = _mag_y_accum = _mag_z_accum = 0;

    last_update = micros(); // record time of update

    // rotate to the desired orientation
    Vector3f rot_mag = Vector3f(mag_x,mag_y,mag_z);
    if (product_id == AP_COMPASS_TYPE_HMC5883L) {
        rot_mag.rotate(ROTATION_YAW_90);
    }
    rot_mag.rotate(_orientation);

    rot_mag += _offset.get();
    mag_x = rot_mag.x;
    mag_y = rot_mag.y;
    mag_z = rot_mag.z;
    healthy = true;

    return true;
}

// set orientation
void
AP_Compass_HMC5843::set_orientation(enum Rotation rotation)
{
    _orientation = rotation;
}