File content as of revision 3:37fb1e2aacf3:

#include "stm32f103c8t6.h"
#include "mbed.h"
#include "MPU9250.h"

float sum = 0;
uint32_t sumCount = 0;
char buffer[14];

MPU9250 mpu9250;

Timer t;

int main()
{

    confSysClock();
    Serial pc(PA_2, PA_3);//pc(USBTX, USBRX); // tx, rx
    pc.baud(115200);

    //Set up I2C
    i2c.frequency(400000);  // use fast (400 kHz) I2C

    pc.printf("CPU SystemCoreClock is %d Hz\r\n", SystemCoreClock);

    t.start();

    // Read the WHO_AM_I register, this is a good test of communication
    uint8_t whoami = mpu9250.readByte(MPU9250_ADDRESS, WHO_AM_I_MPU9250);  // Read WHO_AM_I register for MPU-9250
    pc.printf("I AM 0x%x\n\r", whoami);
    pc.printf("I SHOULD BE 0x71\n\r");

    if (whoami == 0x73) { // WHO_AM_I should always be 0x68
        pc.printf("MPU9250 WHO_AM_I is 0x%x\n\r", whoami);
        pc.printf("MPU9250 is online...\n\r");
        sprintf(buffer, "0x%x", whoami);
        wait(1);

        mpu9250.resetMPU9250(); // Reset registers to default in preparation for device calibration
        mpu9250.MPU9250SelfTest(SelfTest); // Start by performing self test and reporting values
        pc.printf("x-axis self test: acceleration trim within : %f % of factory value\n\r", SelfTest[0]);
        pc.printf("y-axis self test: acceleration trim within : %f % of factory value\n\r", SelfTest[1]);
        pc.printf("z-axis self test: acceleration trim within : %f % of factory value\n\r", SelfTest[2]);
        pc.printf("x-axis self test: gyration trim within : %f % of factory value\n\r", SelfTest[3]);
        pc.printf("y-axis self test: gyration trim within : %f % of factory value\n\r", SelfTest[4]);
        pc.printf("z-axis self test: gyration trim within : %f % of factory value\n\r", SelfTest[5]);
        mpu9250.calibrateMPU9250(gyroBias, accelBias); // Calibrate gyro and accelerometers, load biases in bias registers
        pc.printf("x gyro bias = %f\n\r", gyroBias[0]);
        pc.printf("y gyro bias = %f\n\r", gyroBias[1]);
        pc.printf("z gyro bias = %f\n\r", gyroBias[2]);
        pc.printf("x accel bias = %f\n\r", accelBias[0]);
        pc.printf("y accel bias = %f\n\r", accelBias[1]);
        pc.printf("z accel bias = %f\n\r", accelBias[2]);
        wait(2);

        mpu9250.initMPU9250();
        pc.printf("MPU9250 initialized for active data mode....\n\r"); // Initialize device for active mode read of acclerometer, gyroscope, and temperature
        mpu9250.initAK8963(magCalibration);
        pc.printf("AK8963 initialized for active data mode....\n\r"); // Initialize device for active mode read of magnetometer
        pc.printf("Accelerometer full-scale range = %f  g\n\r", 2.0f*(float)(1<<Ascale));
        pc.printf("Gyroscope full-scale range = %f  deg/s\n\r", 250.0f*(float)(1<<Gscale));
        if(Mscale == 0) pc.printf("Magnetometer resolution = 14  bits\n\r");
        if(Mscale == 1) pc.printf("Magnetometer resolution = 16  bits\n\r");
        if(Mmode == 2) pc.printf("Magnetometer ODR = 8 Hz\n\r");
        if(Mmode == 6) pc.printf("Magnetometer ODR = 100 Hz\n\r");
        wait(1);
    } else {
        pc.printf("Could not connect to MPU9250: \n\r");
        pc.printf("%#x \n",  whoami);

        sprintf(buffer, "WHO_AM_I 0x%x", whoami);
        while(1) ; // Loop forever if communication doesn't happen
    }
    mpu9250.getAres(); // Get accelerometer sensitivity
    mpu9250.getGres(); // Get gyro sensitivity
    mpu9250.getMres(); // Get magnetometer sensitivity
    pc.printf("Accelerometer sensitivity is %f LSB/g \n\r", 1.0f/aRes);
    pc.printf("Gyroscope sensitivity is %f LSB/deg/s \n\r", 1.0f/gRes);
    pc.printf("Magnetometer sensitivity is %f LSB/G \n\r", 1.0f/mRes);
    magbias[0] = +470.;  // User environmental x-axis correction in milliGauss, should be automatically calculated
    magbias[1] = +120.;  // User environmental x-axis correction in milliGauss
    magbias[2] = +125.;  // User environmental x-axis correction in milliGauss


    while(1) {

        // If intPin goes high, all data registers have new data
        if(mpu9250.readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01) {  // On interrupt, check if data ready interrupt

            mpu9250.readAccelData(accelCount);  // Read the x/y/z adc values
            // Now we'll calculate the accleration value into actual g's
            ax = (float)accelCount[0]*aRes - accelBias[0];  // get actual g value, this depends on scale being set
            ay = (float)accelCount[1]*aRes - accelBias[1];
            az = (float)accelCount[2]*aRes - accelBias[2];

            mpu9250.readGyroData(gyroCount);  // Read the x/y/z adc values
            // Calculate the gyro value into actual degrees per second
            gx = (float)gyroCount[0]*gRes - gyroBias[0];  // get actual gyro value, this depends on scale being set
            gy = (float)gyroCount[1]*gRes - gyroBias[1];
            gz = (float)gyroCount[2]*gRes - gyroBias[2];

            mpu9250.readMagData(magCount);  // Read the x/y/z adc values
            // Calculate the magnetometer values in milliGauss
            // Include factory calibration per data sheet and user environmental corrections
            mx = (float)magCount[0]*mRes*magCalibration[0] - magbias[0];  // get actual magnetometer value, this depends on scale being set
            my = (float)magCount[1]*mRes*magCalibration[1] - magbias[1];
            mz = (float)magCount[2]*mRes*magCalibration[2] - magbias[2];
        }

        Now = t.read_us();
        deltat = (float)((Now - lastUpdate)/1000000.0f) ; // set integration time by time elapsed since last filter update
        lastUpdate = Now;

        sum += deltat;
        sumCount++;

//    if(lastUpdate - firstUpdate > 10000000.0f) {
//     beta = 0.04;  // decrease filter gain after stabilized
//     zeta = 0.015; // increasey bias drift gain after stabilized
//   }

        // Pass gyro rate as rad/s
//  mpu9250.MadgwickQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f,  my,  mx, mz);
        mpu9250.MahonyQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f, my, mx, mz);

        // Serial print and/or display at 0.5 s rate independent of data rates
        delt_t = t.read_ms() - count;
        if (delt_t > 500) { // update LCD once per half-second independent of read rate

            pc.printf("ax = %f", 1000*ax);
            pc.printf(" ay = %f", 1000*ay);
            pc.printf(" az = %f  mg\n\r", 1000*az);

            pc.printf("gx = %f", gx);
            pc.printf(" gy = %f", gy);
            pc.printf(" gz = %f  deg/s\n\r", gz);

            pc.printf("gx = %f", mx);
            pc.printf(" gy = %f", my);
            pc.printf(" gz = %f  mG\n\r", mz);

            tempCount = mpu9250.readTempData();  // Read the adc values
            temperature = ((float) tempCount) / 333.87f + 21.0f; // Temperature in degrees Centigrade
            pc.printf(" temperature = %f  C\n\r", temperature);

            pc.printf("q0 = %f\n\r", q[0]);
            pc.printf("q1 = %f\n\r", q[1]);
            pc.printf("q2 = %f\n\r", q[2]);
            pc.printf("q3 = %f\n\r", q[3]);

            /*    lcd.clear();
                lcd.printString("MPU9250", 0, 0);
                lcd.printString("x   y   z", 0, 1);
                sprintf(buffer, "%d %d %d mg", (int)(1000.0f*ax), (int)(1000.0f*ay), (int)(1000.0f*az));
                lcd.printString(buffer, 0, 2);
                sprintf(buffer, "%d %d %d deg/s", (int)gx, (int)gy, (int)gz);
                lcd.printString(buffer, 0, 3);
                sprintf(buffer, "%d %d %d mG", (int)mx, (int)my, (int)mz);
                lcd.printString(buffer, 0, 4);
             */
            // Define output variables from updated quaternion---these are Tait-Bryan angles, commonly used in aircraft orientation.
            // In this coordinate system, the positive z-axis is down toward Earth.
            // Yaw is the angle between Sensor x-axis and Earth magnetic North (or true North if corrected for local declination, looking down on the sensor positive yaw is counterclockwise.
            // Pitch is angle between sensor x-axis and Earth ground plane, toward the Earth is positive, up toward the sky is negative.
            // Roll is angle between sensor y-axis and Earth ground plane, y-axis up is positive roll.
            // These arise from the definition of the homogeneous rotation matrix constructed from quaternions.
            // Tait-Bryan angles as well as Euler angles are non-commutative; that is, the get the correct orientation the rotations must be
            // applied in the correct order which for this configuration is yaw, pitch, and then roll.
            // For more see http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles which has additional links.
            yaw   = atan2(2.0f * (q[1] * q[2] + q[0] * q[3]), q[0] * q[0] + q[1] * q[1] - q[2] * q[2] - q[3] * q[3]);
            pitch = -asin(2.0f * (q[1] * q[3] - q[0] * q[2]));
            roll  = atan2(2.0f * (q[0] * q[1] + q[2] * q[3]), q[0] * q[0] - q[1] * q[1] - q[2] * q[2] + q[3] * q[3]);
            pitch *= 180.0f / PI;
            yaw   *= 180.0f / PI;
            yaw   -= 13.8f; // Declination at Danville, California is 13 degrees 48 minutes and 47 seconds on 2014-04-04
            roll  *= 180.0f / PI;

            pc.printf("Yaw, Pitch, Roll: %f %f %f\n\r", yaw, pitch, roll);
            pc.printf("average rate = %f\n\r", (float) sumCount/sum);
//    sprintf(buffer, "YPR: %f %f %f", yaw, pitch, roll);
//    lcd.printString(buffer, 0, 4);
//    sprintf(buffer, "rate = %f", (float) sumCount/sum);
//    lcd.printString(buffer, 0, 5);

            myled= !myled;
            count = t.read_ms();

            if(count > 1<<21) {
                t.start(); // start the timer over again if ~30 minutes has passed
                count = 0;
                deltat= 0;
                lastUpdate = t.read_us();
            }
            sum = 0;
            sumCount = 0;
        }
    }
}