Diff: adapt/compass.cpp

Revision:

17:323fc40376d5

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/adapt/compass.cpp	Thu Apr 03 17:18:58 2014 +0000
@@ -0,0 +1,303 @@
+#include <compass.h>
+#include <math.h>
+
+SPI spi(p5, p6, p7); // mosi, miso, sclk
+DigitalOut cs(p8);
+
+// Defines ////////////////////////////////////////////////////////////////
+
+#define D_WHO_ID    0x49
+#define DLM_WHO_ID  0x3C
+
+// Constructors ////////////////////////////////////////////////////////////////
+
+Compass::Compass(void){
+    //These values lead to an assumed magnetometer bias of 0.
+    m_min = (Compass::vector<int16_t>){-32767, -32767, -32767};
+    m_max = (Compass::vector<int16_t>){+32767, +32767, +32767};
+    //automatically determine which device is being used
+    _device = device_auto;
+    //initialize chip select to high (not active)
+    cs=1;
+}
+
+bool Compass::init(deviceType device){
+    // Setup the spi for 8 bit data, low steady state clock,
+    // rising edge capture, with a 1MHz clock rate
+    spi.format(8,0);
+    spi.frequency(1000000);
+  
+    // determine device type if necessary
+    if (device == device_auto){
+        if (testReg(WHO_AM_I) == D_WHO_ID){
+            // device responds with D ID; it's a D.
+            device = device_D;
+            device_id = 1;
+        }else{
+            // device hasn't responded meaningfully, so give up
+            return false;
+        }
+    }
+
+    _device = device;
+
+    // set device addresses and translated register addresses
+    switch (device){
+        case device_D:
+            translated_regs[-OUT_X_L_M] = D_OUT_X_L_M;
+            translated_regs[-OUT_X_H_M] = D_OUT_X_H_M;
+            translated_regs[-OUT_Y_L_M] = D_OUT_Y_L_M;
+            translated_regs[-OUT_Y_H_M] = D_OUT_Y_H_M;
+            translated_regs[-OUT_Z_L_M] = D_OUT_Z_L_M;
+            translated_regs[-OUT_Z_H_M] = D_OUT_Z_H_M;
+        break;
+    }
+    return true;
+}
+
+/*
+Enables the Compass's accelerometer and magnetometer. Also:
+- Sets sensor full scales (gain) to default power-on values, which are
+  +/- 2 g for accelerometer and +/- 1.3 gauss for magnetometer
+  (+/- 4 gauss on LSM303D).
+- Selects 50 Hz ODR (output data rate) for accelerometer and 7.5 Hz
+  ODR for magnetometer (6.25 Hz on LSM303D). (These are the ODR
+  settings for which the electrical characteristics are specified in
+  the datasheets.)
+- Enables high resolution modes (if available).
+Note that this function will also reset other settings controlled by
+the registers it writes to.
+*/
+void Compass::enableDefault(void){
+    if (_device == device_D){
+        // Accelerometer
+        writeReg(CTRL0, 0x40);
+        writeReg(CTRL2, 0x00);
+
+        // 0x57 = 0b01010111
+        // AODR = 0101 (50 Hz ODR); AZEN = AYEN = AXEN = 1 (all axes enabled)
+        writeReg(CTRL1, 0xA7);
+
+        // Magnetometer
+
+        // 0x64 = 0b01100100
+        // M_RES = 11 (high resolution mode); M_ODR = 001 (6.25 Hz ODR)
+        writeReg(CTRL5, 0x74);
+
+        // 0x20 = 0b00100000
+        // MFS = 01 (+/- 4 gauss full scale)
+        writeReg(CTRL6, 0x20);
+
+        // 0x00 = 0b00000000
+        // MLP = 0 (low power mode off); MD = 00 (continuous-conversion mode)
+        writeReg(CTRL7, 0x00);
+    }
+}
+
+// Writes an accelerometer register
+void Compass::writeAccReg(regAddr reg, int value){
+    cs = 0;
+    spi.write(reg);
+    spi.write(value);
+    cs = 1;
+}
+
+// Reads an accelerometer register
+int Compass::readAccReg(regAddr reg){
+    int value;
+    cs = 0;
+    spi.write(reg | 0x80);
+    value = spi.write(0x00);
+    cs = 1;
+    return value;
+}
+
+// Writes a magnetometer register
+void Compass::writeMagReg(regAddr reg, int value){
+    cs = 0;
+    spi.write(reg);
+    spi.write(value);
+    cs = 1; 
+}
+
+// Reads a magnetometer register
+int Compass::readMagReg(regAddr reg){
+    int value;
+
+    // if dummy register address (magnetometer Y/Z), look up actual translated address (based on device type)
+    if (reg < 0){
+        reg = translated_regs[-reg];
+    }
+    cs = 0;
+    spi.write(reg | (0x80));
+    value = spi.write(0x00);
+    cs = 1;
+
+    return value;
+}
+
+void Compass::writeReg(regAddr reg, int value){
+  // Use writeMagReg so it can translate OUT_[XYZ]_[HL]_M
+    if (_device == device_D || reg < CTRL_REG1_A){
+        writeMagReg(reg, value);
+    }
+    else{
+        writeAccReg(reg, value);
+    }
+}
+
+// Note that this function will not work for reading TEMP_OUT_H_M and TEMP_OUT_L_M on the DLHC.
+// To read those two registers, use readMagReg() instead.
+int Compass::readReg(regAddr reg){
+    // Use writeMagReg so it can translate OUT_[XYZ]_[HL]_M
+    if (_device == device_D || reg < CTRL_REG1_A){
+        return readMagReg(reg);
+    }
+    else{
+        return readAccReg(reg);
+    }
+}
+
+// Reads the 3 accelerometer channels and stores them in vector a
+void Compass::readAcc(void){
+    char reg = OUT_X_L_A | (3 << 6);
+    char valuesAcc[6];
+    cs = 0;
+    spi.write(reg);
+    for(int i=0;i<6;i++){
+        valuesAcc[i] = spi.write(0x00);
+    }
+    cs = 1;
+    
+    // combine high and low bytes
+    // This no longer drops the lowest 4 bits of the readings from the DLH/DLM/DLHC, which are always 0
+    // (12-bit resolution, left-aligned). The D has 16-bit resolution
+    a.x = (int16_t)(valuesAcc[1] << 8 | valuesAcc[0]);
+    a.y = (int16_t)(valuesAcc[3] << 8 | valuesAcc[2]);
+    a.z = (int16_t)(valuesAcc[5] << 8 | valuesAcc[4]);
+}
+
+// Reads the 3 magnetometer channels and stores them in vector m
+void Compass::readMag(void){
+    int reg;
+    int values[6];
+    
+    reg = 0xC8;
+    
+    device_id = readReg(CTRL5);
+    wait_ms(50);
+  
+    cs = 0;
+    spi.write(reg);
+    for(int i=0;i<6;i++){
+        values[i] = spi.write(0x00);
+    }
+    cs = 1;
+
+    char xlm, xhm, ylm, yhm, zlm, zhm;
+
+    //if (_device == device_D){
+        /// D: X_L, X_H, Y_L, Y_H, Z_L, Z_H
+        xlm = values[0];
+        xhm = values[1];
+        ylm = values[2];
+        yhm = values[3];
+        zlm = values[4];
+        zhm = values[5];
+   // }
+    // combine high and low bytes
+    m.x = (int16_t)(xhm << 8 | xlm);
+    m.y = (int16_t)(yhm << 8 | ylm);
+    m.z = (int16_t)(zhm << 8 | zlm);
+}
+
+// Reads all 6 channels of the LSM303 and stores them in the object variables
+void Compass::read(void){
+    readAcc();
+    readMag();
+}
+
+/*
+Returns the angular difference in the horizontal plane between a
+default vector and north, in degrees.
+
+The default vector here is chosen to point along the surface of the
+PCB, in the direction of the top of the text on the silkscreen.
+This is the +X axis on the Pololu LSM303D carrier and the -Y axis on
+the Pololu LSM303DLHC, LSM303DLM, and LSM303DLH carriers.
+*/
+float Compass::get_heading(void)
+{
+    if (_device == device_D){
+        vector<int> params = {1,0,0};
+        return get_heading(params);
+    }else{
+        return get_heading((vector<int>){0, -1, 0});
+    }
+}
+
+/*
+Returns the angular difference in the horizontal plane between the
+"from" vector and north, in degrees.
+
+Description of heading algorithm:
+Shift and scale the magnetic reading based on calibration data to find
+the North vector. Use the acceleration readings to determine the Up
+vector (gravity is measured as an upward acceleration). The cross
+product of North and Up vectors is East. The vectors East and North
+form a basis for the horizontal plane. The From vector is projected
+into the horizontal plane and the angle between the projected vector
+and horizontal north is returned.
+*/
+template <typename T> float Compass::get_heading(vector<T> from){
+    vector<int32_t> temp_m = {m.x, m.y, m.z};
+
+    // subtract offset (average of min and max) from magnetometer readings
+    temp_m.x -= ((int32_t)m_min.x + m_max.x) / 2;
+    temp_m.y -= ((int32_t)m_min.y + m_max.y) / 2;
+    temp_m.z -= ((int32_t)m_min.z + m_max.z) / 2;
+
+    // compute E and N
+    vector<float> E;
+    vector<float> N;
+    vector_cross(&temp_m, &a, &E);
+    vector_normalize(&E);
+    vector_cross(&a, &E, &N);
+    vector_normalize(&N);
+
+    // compute heading
+    float heading = atan2(vector_dot(&E, &from), vector_dot(&N, &from)) * 180 / 3.14159265359;
+    if (heading < 0) heading += 360;
+    return heading;
+}
+
+template <typename Ta, typename Tb, typename To> void Compass::vector_cross(const vector<Ta> *a,const vector<Tb> *b, vector<To> *out){
+    out->x = (a->y * b->z) - (a->z * b->y);
+    out->y = (a->z * b->x) - (a->x * b->z);
+    out->z = (a->x * b->y) - (a->y * b->x);
+}
+
+template <typename Ta, typename Tb> float Compass::vector_dot(const vector<Ta> *a, const vector<Tb> *b){
+    return (a->x * b->x) + (a->y * b->y) + (a->z * b->z);
+}
+
+void Compass::vector_normalize(vector<float> *a){
+    float mag = sqrt(vector_dot(a, a));
+    a->x /= mag;
+    a->y /= mag;
+    a->z /= mag;
+}
+
+// Private Methods //////////////////////////////////////////////////////////////
+
+int Compass::testReg(regAddr reg){
+    // Select the device by seting chip select low
+    cs = 0;
+    // Send 0x8f, the command to read the WHOAMI register
+    spi.write(reg | 0x80);
+    // Send a dummy byte to receive the contents of the WHOAMI register
+    int whoami = spi.write(0x00);
+    // Deselect the device
+    cs = 1;    
+    return whoami;
+}
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