Diff: IMU/Sensors/Comp/HMC5883.cpp

Revision:

0:3e7450f1a938

Child:

4:f62337b907e5

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/IMU/Sensors/Comp/HMC5883.cpp	Tue Aug 27 17:37:06 2013 +0000
@@ -0,0 +1,85 @@
+#include "HMC5883.h"
+
+HMC5883::HMC5883(PinName sda, PinName scl) : I2C_Sensor(sda, scl, HMC5883_I2C_ADDRESS)
+{   
+    offset[0] = -155; // offset calculated by hand... (min + ((max - min) / 2)
+    offset[1] = -142; // TODO: make this automatic with saving to filesystem
+    offset[2] = -33.5;
+    
+    // load calibration values
+    //loadCalibrationValues(scale, 3, "COMPASS_SCALE.txt");
+    //loadCalibrationValues(offset, 3, "COMPASS_OFFSET.txt");
+    
+    // initialize HMC5883
+    writeRegister(HMC5883_CONF_REG_A, 0x78);                // 8 samples, 75Hz output, normal mode
+    //writeRegister(HMC5883_CONF_REG_A, 0x19);              // 8 samples, 75Hz output, test mode! (should get constant values from measurement, see datasheet)
+    writeRegister(HMC5883_CONF_REG_B, 0x20);                // Gain for +- 1.3 gauss (earth compass ~0.6 gauss)
+    writeRegister(HMC5883_MODE_REG, 0x00);                  // continuous measurement-mode
+}
+
+void HMC5883::read()
+{
+    readraw();
+    for(int i = 0; i < 3; i++)
+        data[i] = (float)(raw[i]) - offset[i];
+}
+
+void HMC5883::calibrate(int s)
+{
+    int Min[3];                                             // values for achieved maximum and minimum amplitude in calibrating environment
+    int Max[3];
+    
+    Timer calibrate_timer;                                  // timer to know when calibration is finished
+    calibrate_timer.start();
+    
+    while(calibrate_timer.read() < s)                       // take measurements for s seconds
+    {
+        readraw();
+        for(int i = 0; i < 3; i++) {
+            Min[i] = Min[i] < raw[i] ? Min[i] : raw[i];      // after each measurement check if there's a new minimum or maximum
+            Max[i] = Max[i] > raw[i] ? Max[i] : raw[i];
+        }
+    }
+    
+    for(int i = 0; i < 3; i++) {
+        //scale[i]= 2000 / (float)(Max[i]-Min[i]);            // calculate scale and offset out of the measured maxima and minima
+        //offset[i]= 1000 - (float)(Max[i]) * scale[i];       // the lower bound is -1000, the higher one 1000
+    }
+    
+    //saveCalibrationValues(scale, 3, "COM_SCALE");   // save new scale and offset values to flash
+    //saveCalibrationValues(offset, 3, "COM_OFFSE");
+}
+
+void HMC5883::readraw()
+{
+    char buffer[6];                                         // 8-Bit pieces of axis data
+    
+    readMultiRegister(HMC5883_DATA_OUT_X_MSB, buffer, 6);   // read axis registers using I2C
+    
+    raw[0] = (short) (buffer[0] << 8 | buffer[1]);          // join 8-Bit pieces to 16-bit short integers
+    raw[1] = (short) (buffer[4] << 8 | buffer[5]);          // X, Z and Y (yes, order is stupid like this, see datasheet)
+    raw[2] = (short) (buffer[2] << 8 | buffer[3]);
+}
+
+float HMC5883::get_angle()
+{
+    #define RAD2DEG     57.295779513082320876798154814105
+
+    float Heading;
+    
+    Heading = RAD2DEG * atan2(data[0],data[1]);
+    Heading += 1.367;                   // correction of the angle between geographical and magnetical north direction, called declination
+                                        // if you need an east-declination += DecAngle, if you need west-declination -= DecAngle
+                                        // for me in Switzerland, Bern it's ca. 1.367 degree east
+                                        // see:     http://magnetic-declination.com/
+                                        // for me:  http://www.swisstopo.admin.ch/internet/swisstopo/de/home/apps/calc/declination.html
+    if(Heading < 0)  
+        Heading += 360;                 // minimum 0 degree
+        
+    if(Heading > 360)   
+        Heading -= 360;                 // maximum 360 degree
+
+    return Heading;
+}
+    
+