ardupilot/libraries/AP_Compass/AP_Compass.cpp

116 lines
3.1 KiB
C++

/*
AP_Compass.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)
Variables:
heading : Magnetic heading
heading_X : Magnetic heading X component
heading_Y : Magnetic heading Y component
mag_X : Raw X axis magnetometer data
mag_Y : Raw Y axis magnetometer data
mag_Z : Raw Z axis magnetometer data
Methods:
init() : initialization of I2C and sensor
update() : update Sensor data
To do : Calibration of the sensor, code optimization
Mount position : UPDATED
Big capacitor pointing backward, connector forward
*/
extern "C" {
// AVR LibC Includes
#include <math.h>
#include "WConstants.h"
}
#include <Wire.h>
#include "AP_Compass.h"
#define COMPASS_ADDRESS 0x1E
// Constructors ////////////////////////////////////////////////////////////////
AP_Compass::AP_Compass()
{
}
// Public Methods //////////////////////////////////////////////////////////////
void
AP_Compass::init(void)
{
Wire.begin();
Wire.beginTransmission(COMPASS_ADDRESS);
Wire.send(0x02);
Wire.send(0x00); // Set continouos mode (default to 10Hz)
Wire.endTransmission(); // end transmission
}
// update Sensor data
void
AP_Compass::update()
{
int i = 0;
byte buff[6];
Wire.beginTransmission(COMPASS_ADDRESS);
Wire.send(0x03); // sends address to read from
Wire.endTransmission(); // end transmission
//Wire.beginTransmission(COMPASS_ADDRESS);
Wire.requestFrom(COMPASS_ADDRESS, 6); // request 6 bytes from device
while(Wire.available()){
buff[i] = Wire.receive(); // receive one byte
i++;
}
Wire.endTransmission(); // end transmission
// All bytes received?
if (i == 6) {
// MSB byte first, then LSB, X,Y,Z
mag_X = -((((int)buff[0]) << 8) | buff[1]); // X axis
mag_Y = ((((int)buff[2]) << 8) | buff[3]); // Y axis
mag_Z = -((((int)buff[4]) << 8) | buff[5]); // Z axis
}
}
void
AP_Compass::calculate(float roll, float pitch)
{
float head_X;
float head_Y;
float cos_roll;
float sin_roll;
float cos_pitch;
float sin_pitch;
cos_roll = cos(roll); // Optimization, you can get this out of the matrix DCM?
sin_roll = sin(roll);
cos_pitch = cos(pitch);
sin_pitch = sin(pitch);
// Tilt compensated Magnetic field X component:
head_X = mag_X * cos_pitch + mag_Y * sin_roll * sin_pitch + mag_Z * cos_roll * sin_pitch;
// Tilt compensated Magnetic field Y component:
head_Y = mag_Y * cos_roll - mag_Z * sin_roll;
// Magnetic heading
heading = atan2(-head_Y, head_X);
ground_course = (degrees(heading) + 180) * 100;
// Optimization for external DCM use. calculate normalized components
heading_X = cos(heading);
heading_Y = sin(heading);
}