File content as of revision 4:43a6ec1af346:

#include "mbed.h"
#include "LSM9DS1.h"
#include "Wireless.h"
//#include "USBKeyboard.h"
//#include "MahonyAHRS.h"
#define PI 3.14159
// Earth's magnetic field varies by location. Add or subtract
// a declination to get a more accurate heading. Calculate
// your's here:
// http://www.ngdc.noaa.gov/geomag-web/#declination
#define DECLINATION -4.94 // Declination (degrees) in Atlanta,GA.

DigitalOut led1(LED1);
DigitalOut led2(LED2);
DigitalOut led3(LED3);
DigitalOut led4(LED4);
Serial pc(USBTX, USBRX);
DigitalIn pb1(p17);
//USBKeyboard keyboard;
// Calculate pitch, roll, and heading.
// Pitch/roll calculations taken from this app note:
// http://cache.freescale.com/files/sensors/doc/app_note/AN3461.pdf?fpsp=1
// Heading calculations taken from this app note:
// http://www51.honeywell.com/aero/common/documents/myaerospacecatalog-documents/Defense_Brochures-documents/Magnetic__Literature_Application_notes-documents/AN203_Compass_Heading_Using_Magnetometers.pdf
#include <math.h>

//---------------------------------------------------------------------------------------------------
// Definitions

#define sampleFreq  952.0f      // sample frequency in Hz
#define betaDef     0.1f        // 2 * proportional gain

//---------------------------------------------------------------------------------------------------
// Variable definitions

volatile float beta = betaDef;                              // 2 * proportional gain (Kp)
volatile float q0 = 1.0f, q1 = 0.0f, q2 = 0.0f, q3 = 0.0f;  // quaternion of sensor frame relative to auxiliary frame

//---------------------------------------------------------------------------------------------------
// Function declarations

float invSqrt(float x);

//====================================================================================================
// Functions

//---------------------------------------------------------------------------------------------------
// AHRS algorithm update
void MadgwickAHRSupdateIMU(float gx, float gy, float gz, float ax, float ay, float az);
void MadgwickAHRSupdate(float gx, float gy, float gz, float ax, float ay, float az, float mx, float my, float mz)
{
    float recipNorm;
    float s0, s1, s2, s3;
    float qDot1, qDot2, qDot3, qDot4;
    float hx, hy;
    float _2q0mx, _2q0my, _2q0mz, _2q1mx, _2bx, _2bz, _4bx, _4bz, _2q0, _2q1, _2q2, _2q3, _2q0q2, _2q2q3, q0q0, q0q1, q0q2, q0q3, q1q1, q1q2, q1q3, q2q2, q2q3, q3q3;

    // Use IMU algorithm if magnetometer measurement invalid (avoids NaN in magnetometer normalisation)
    if((mx == 0.0f) && (my == 0.0f) && (mz == 0.0f)) {
        MadgwickAHRSupdateIMU(gx, gy, gz, ax, ay, az);
        return;
    }

    // Rate of change of quaternion from gyroscope
    qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz);
    qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy);
    qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx);
    qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx);

    // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
    if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {

        // Normalise accelerometer measurement
        recipNorm = invSqrt(ax * ax + ay * ay + az * az);
        ax *= recipNorm;
        ay *= recipNorm;
        az *= recipNorm;

        // Normalise magnetometer measurement
        recipNorm = invSqrt(mx * mx + my * my + mz * mz);
        mx *= recipNorm;
        my *= recipNorm;
        mz *= recipNorm;

        // Auxiliary variables to avoid repeated arithmetic
        _2q0mx = 2.0f * q0 * mx;
        _2q0my = 2.0f * q0 * my;
        _2q0mz = 2.0f * q0 * mz;
        _2q1mx = 2.0f * q1 * mx;
        _2q0 = 2.0f * q0;
        _2q1 = 2.0f * q1;
        _2q2 = 2.0f * q2;
        _2q3 = 2.0f * q3;
        _2q0q2 = 2.0f * q0 * q2;
        _2q2q3 = 2.0f * q2 * q3;
        q0q0 = q0 * q0;
        q0q1 = q0 * q1;
        q0q2 = q0 * q2;
        q0q3 = q0 * q3;
        q1q1 = q1 * q1;
        q1q2 = q1 * q2;
        q1q3 = q1 * q3;
        q2q2 = q2 * q2;
        q2q3 = q2 * q3;
        q3q3 = q3 * q3;

        // Reference direction of Earth's magnetic field
        hx = mx * q0q0 - _2q0my * q3 + _2q0mz * q2 + mx * q1q1 + _2q1 * my * q2 + _2q1 * mz * q3 - mx * q2q2 - mx * q3q3;
        hy = _2q0mx * q3 + my * q0q0 - _2q0mz * q1 + _2q1mx * q2 - my * q1q1 + my * q2q2 + _2q2 * mz * q3 - my * q3q3;
        _2bx = sqrt(hx * hx + hy * hy);
        _2bz = -_2q0mx * q2 + _2q0my * q1 + mz * q0q0 + _2q1mx * q3 - mz * q1q1 + _2q2 * my * q3 - mz * q2q2 + mz * q3q3;
        _4bx = 2.0f * _2bx;
        _4bz = 2.0f * _2bz;

        // Gradient decent algorithm corrective step
        s0 = -_2q2 * (2.0f * q1q3 - _2q0q2 - ax) + _2q1 * (2.0f * q0q1 + _2q2q3 - ay) - _2bz * q2 * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (-_2bx * q3 + _2bz * q1) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + _2bx * q2 * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
        s1 = _2q3 * (2.0f * q1q3 - _2q0q2 - ax) + _2q0 * (2.0f * q0q1 + _2q2q3 - ay) - 4.0f * q1 * (1 - 2.0f * q1q1 - 2.0f * q2q2 - az) + _2bz * q3 * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (_2bx * q2 + _2bz * q0) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + (_2bx * q3 - _4bz * q1) * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
        s2 = -_2q0 * (2.0f * q1q3 - _2q0q2 - ax) + _2q3 * (2.0f * q0q1 + _2q2q3 - ay) - 4.0f * q2 * (1 - 2.0f * q1q1 - 2.0f * q2q2 - az) + (-_4bx * q2 - _2bz * q0) * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (_2bx * q1 + _2bz * q3) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + (_2bx * q0 - _4bz * q2) * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
        s3 = _2q1 * (2.0f * q1q3 - _2q0q2 - ax) + _2q2 * (2.0f * q0q1 + _2q2q3 - ay) + (-_4bx * q3 + _2bz * q1) * (_2bx * (0.5f - q2q2 - q3q3) + _2bz * (q1q3 - q0q2) - mx) + (-_2bx * q0 + _2bz * q2) * (_2bx * (q1q2 - q0q3) + _2bz * (q0q1 + q2q3) - my) + _2bx * q1 * (_2bx * (q0q2 + q1q3) + _2bz * (0.5f - q1q1 - q2q2) - mz);
        recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude
        s0 *= recipNorm;
        s1 *= recipNorm;
        s2 *= recipNorm;
        s3 *= recipNorm;

        // Apply feedback step
        qDot1 -= beta * s0;
        qDot2 -= beta * s1;
        qDot3 -= beta * s2;
        qDot4 -= beta * s3;
    }

    // Integrate rate of change of quaternion to yield quaternion
    q0 += qDot1 * (1.0f / sampleFreq);
    q1 += qDot2 * (1.0f / sampleFreq);
    q2 += qDot3 * (1.0f / sampleFreq);
    q3 += qDot4 * (1.0f / sampleFreq);

    // Normalise quaternion
    recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
    q0 *= recipNorm;
    q1 *= recipNorm;
    q2 *= recipNorm;
    q3 *= recipNorm;
}

//---------------------------------------------------------------------------------------------------
// IMU algorithm update

void MadgwickAHRSupdateIMU(float gx, float gy, float gz, float ax, float ay, float az)
{
    float recipNorm;
    float s0, s1, s2, s3;
    float qDot1, qDot2, qDot3, qDot4;
    float _2q0, _2q1, _2q2, _2q3, _4q0, _4q1, _4q2 ,_8q1, _8q2, q0q0, q1q1, q2q2, q3q3;

    // Rate of change of quaternion from gyroscope
    qDot1 = 0.5f * (-q1 * gx - q2 * gy - q3 * gz);
    qDot2 = 0.5f * (q0 * gx + q2 * gz - q3 * gy);
    qDot3 = 0.5f * (q0 * gy - q1 * gz + q3 * gx);
    qDot4 = 0.5f * (q0 * gz + q1 * gy - q2 * gx);

    // Compute feedback only if accelerometer measurement valid (avoids NaN in accelerometer normalisation)
    if(!((ax == 0.0f) && (ay == 0.0f) && (az == 0.0f))) {

        // Normalise accelerometer measurement
        recipNorm = invSqrt(ax * ax + ay * ay + az * az);
        ax *= recipNorm;
        ay *= recipNorm;
        az *= recipNorm;

        // Auxiliary variables to avoid repeated arithmetic
        _2q0 = 2.0f * q0;
        _2q1 = 2.0f * q1;
        _2q2 = 2.0f * q2;
        _2q3 = 2.0f * q3;
        _4q0 = 4.0f * q0;
        _4q1 = 4.0f * q1;
        _4q2 = 4.0f * q2;
        _8q1 = 8.0f * q1;
        _8q2 = 8.0f * q2;
        q0q0 = q0 * q0;
        q1q1 = q1 * q1;
        q2q2 = q2 * q2;
        q3q3 = q3 * q3;

        // Gradient decent algorithm corrective step
        s0 = _4q0 * q2q2 + _2q2 * ax + _4q0 * q1q1 - _2q1 * ay;
        s1 = _4q1 * q3q3 - _2q3 * ax + 4.0f * q0q0 * q1 - _2q0 * ay - _4q1 + _8q1 * q1q1 + _8q1 * q2q2 + _4q1 * az;
        s2 = 4.0f * q0q0 * q2 + _2q0 * ax + _4q2 * q3q3 - _2q3 * ay - _4q2 + _8q2 * q1q1 + _8q2 * q2q2 + _4q2 * az;
        s3 = 4.0f * q1q1 * q3 - _2q1 * ax + 4.0f * q2q2 * q3 - _2q2 * ay;
        recipNorm = invSqrt(s0 * s0 + s1 * s1 + s2 * s2 + s3 * s3); // normalise step magnitude
        s0 *= recipNorm;
        s1 *= recipNorm;
        s2 *= recipNorm;
        s3 *= recipNorm;

        // Apply feedback step
        qDot1 -= beta * s0;
        qDot2 -= beta * s1;
        qDot3 -= beta * s2;
        qDot4 -= beta * s3;
    }

    // Integrate rate of change of quaternion to yield quaternion
    q0 += qDot1 * (1.0f / sampleFreq);
    q1 += qDot2 * (1.0f / sampleFreq);
    q2 += qDot3 * (1.0f / sampleFreq);
    q3 += qDot4 * (1.0f / sampleFreq);

    // Normalise quaternion
    recipNorm = invSqrt(q0 * q0 + q1 * q1 + q2 * q2 + q3 * q3);
    q0 *= recipNorm;
    q1 *= recipNorm;
    q2 *= recipNorm;
    q3 *= recipNorm;
}

//---------------------------------------------------------------------------------------------------
// Fast inverse square-root
// See: http://en.wikipedia.org/wiki/Fast_inverse_square_root

float invSqrt(float x)
{
    float halfx = 0.5f * x;
    float y = x;
    long i = *(long*)&y;
    i = 0x5f3759df - (i>>1);
    y = *(float*)&i;
    y = y * (1.5f - (halfx * y * y));
    return y;
}

//====================================================================================================
// END OF CODE
//====================================================================================================





float correctHeading(float currHeading, float forward)
{
    float newHeading = currHeading - forward;
    if(newHeading < 0) newHeading = 360 + newHeading;
    return newHeading;
}

float printAttitude(float ax, float ay, float az, float mx, float my, float mz)
{
    float roll = atan2(ay, az);
    float pitch = atan2(-ax, sqrt(ay * ay + az * az));
// touchy trig stuff to use arctan to get compass heading (scale is 0..360)
    mx = -mx;
    float heading;
    if (my == 0.0)
        heading = (mx < 0.0) ? 180.0 : 0.0;
    else
        heading = atan2(mx, my)*360.0/(2.0*PI);
    //pc.printf("heading atan=%f \n\r",heading);
    heading -= DECLINATION; //correct for geo location
    if(heading>180.0) heading = heading - 360.0;
    else if(heading<-180.0) heading = 360.0 + heading;
    else if(heading<0.0) heading = 360.0  + heading;


    // Convert everything from radians to degrees:
    //heading *= 180.0 / PI;
    pitch *= 180.0 / PI;
    roll  *= 180.0 / PI;

    //pc.printf("Pitch: %f,    Roll: %f degress\n\r",pitch,roll);
    //pc.printf("Magnetic Heading: %f degress\n\r",heading);
    return abs(heading);
}

bool isWalking = false;

Ticker walkingTimer;
Ticker resetStart;
WirelessModule wireless(p9, p10, FOOT_STEP);
float ax ;
float ay ;
float az ;
float gx ;
float gy ;
float gz ;
float mx ;
float my ;
float mz ;
LSM9DS1 IMU(p28, p27, 0xD6, 0x3C);

void printStop()
{
    // pc.printf("stop\n\r");
    wireless.sendDirection(DIR_NONE);
    isWalking = false;
}
void resetForward()
{
    q0 = 1.0f;
    q1 = 0.0f;
    q2 = 0.0f;
    q3 = 0.0f;
    MadgwickAHRSupdate(IMU.calcGyro(gx), IMU.calcGyro(gy), IMU.calcGyro(gz), IMU.calcAccel(ax), IMU.calcAccel(ay), IMU.calcAccel(az), IMU.calcMag(mx), IMU.calcMag(my), IMU.calcMag(mz));
}




int main()
{
    //LSM9DS1 lol(p9, p10, 0x6B, 0x1E);

    pb1.mode(PullUp);
    IMU.begin();
    float forward;
    if (!IMU.begin()) {
        pc.printf("Failed to communicate with LSM9DS1.\n");
    }
    led4 = 1;
    IMU.calibrate(1);
    led4 = 0;
    wait(0.5);
    led1 = 1;
    led4 = 1;
    IMU.calibrateMag(0);
    led4 = 0;
    led2 = 1;
    pc.printf("Press button to set forward direction");
    while(pb1 == 1) {
        IMU.readMag();
        IMU.readAccel();
        ax = IMU.calcAccel(IMU.ax);
        ay = IMU.calcAccel(IMU.ay);
        az = IMU.calcAccel(IMU.az);
        gx = IMU.calcGyro(IMU.gx);
        gy = IMU.calcGyro(IMU.gy);
        gz = IMU.calcGyro(IMU.gz);
        mx = IMU.calcMag(IMU.mx);
        my = IMU.calcMag(IMU.my);
        mz = IMU.calcMag(IMU.mz);
        forward = printAttitude(IMU.calcAccel(IMU.ax), IMU.calcAccel(IMU.ay), IMU.calcAccel(IMU.az), IMU.calcMag(IMU.mx),
                                IMU.calcMag(IMU.my), IMU.calcMag(IMU.mz));;
    }
    led3 = 1;
    resetStart.attach(resetForward, 0.1);
    while(1) {
        while(!IMU.tempAvailable());
        IMU.readTemp();
        while(!IMU.magAvailable(X_AXIS));
        IMU.readMag();
        while(!IMU.accelAvailable());
        IMU.readAccel();
        while(!IMU.gyroAvailable());
        IMU.readGyro();

        MadgwickAHRSupdate(IMU.calcGyro(IMU.gx), IMU.calcGyro(IMU.gy), IMU.calcGyro(IMU.gz), IMU.calcAccel(IMU.ax), IMU.calcAccel(IMU.ay), IMU.calcAccel(IMU.az), IMU.calcMag(IMU.mx), IMU.calcMag(IMU.my), IMU.calcMag(IMU.mz));
        float Yaw_m=atan2(2*q1*q2-2*q0*q3,2*q0*q0+2*q1*q1-1)*180/PI;
        float Pitch_m=-1*asin(2*q1*q3+2*q0*q2)*180/PI;
        float Roll_m=atan2(2*q2*q3-2*q0*q1,2*q0*q0+2*q3*q3-1)*180/PI;

        if( Yaw_m < 0 ) Yaw_m += 360.0;
        //pc.printf("yaw: %f\n\r", Yaw_m);
        //pc.printf("Yaw: %f\n\r Roll: %f\n\r Pitch: %f\n\n\n\r", Yaw_m, Roll_m, Pitch_m);

        if(abs(IMU.calcGyro(IMU.gy)) > 100) {

            //Calculate heading relative to forward direction
            float currHeading = printAttitude(IMU.calcAccel(IMU.ax), IMU.calcAccel(IMU.ay), IMU.calcAccel(IMU.az), IMU.calcMag(IMU.mx),IMU.calcMag(IMU.my), IMU.calcMag(IMU.mz));
            currHeading = correctHeading(currHeading, forward);
            pc.printf("heading: %f\n\r", currHeading);
            //pc.printf("corrected heading: %f\n\r", currHeading);
            //Start timeout to detect when stopped walking
            walkingTimer.attach(printStop, 0.3);

            //Detect direction and send command to main mbed
            if((currHeading > 225 && currHeading < 315) && !isWalking) {
                pc.printf("left\n\r");
                wireless.sendDirection(DIR_LEFT);

                isWalking = true;
            } else if((currHeading > 45 && currHeading < 135) && !isWalking) {
                pc.printf("right\n\r");
                wireless.sendDirection(DIR_RIGHT);
                isWalking = true;
            } else if((currHeading > 135 && currHeading < 225) && !isWalking) {
                pc.printf("down\n\r");
                wireless.sendDirection(DIR_DOWN);
                isWalking = true;
            } else if((currHeading > 315 || currHeading < 45) && !isWalking) {
                pc.printf("up\n\r");
                wireless.sendDirection(DIR_UP);

                isWalking = true;
            }
        }
    }
}