File content as of revision 3:d53674889db3:

/* MPU9250 Basic Example Code
by: Kris Winer
date: April 1, 2014
license: Beerware - Use this code however you'd like. If you 
find it useful you can buy me a beer some time.

Demonstrate basic MPU-9250 functionality including parameterizing the register addresses, initializing the sensor, 
getting properly scaled accelerometer, gyroscope, and magnetometer data out. Added display functions to 
allow display to on breadboard monitor. Addition of 9 DoF sensor fusion using open source Madgwick and 
Mahony filter algorithms. Sketch runs on the 3.3 V 8 MHz Pro Mini and the Teensy 3.1.

-----------------------------------------------------------------------

Adapted by Marijn Jeurissen for the anyThing Connected Sensor Sticker based on Nordic nRF51822
date: February 16, 2018
*/

#include "mbed.h"
#include "MPU9250.h"
#include "SEGGER_RTT.h"
#include "SEGGER_RTT.c"
#include "SEGGER_RTT_printf.c"

float sum = 0, shift = 0;
uint32_t sumCount = 0;
int cycle = 0;
char buffer[14];

MPU9250 mpu9250;
   
Timer t;

short toInt(float x)
{
    return (x >= 0) ? (int)(x + 0.5) : (int)(x - 0.5);
}
int getTime(int counter)
{
    return (int)((counter/60000.0f)+shift);
}
       
int main()
{
    //Set up I2C
    i2c.frequency(400000);  // use fast (400 kHz) I2C    
    SEGGER_RTT_printf(0, "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
    
    if (whoami == 0x71) // WHO_AM_I should always be 0x68
    { 
        SEGGER_RTT_WriteString(0, "MPU9250 is online...\n\n");
        wait(1);
        
        mpu9250.resetMPU9250(); // Reset registers to default in preparation for device calibration
        mpu9250.MPU9250SelfTest(SelfTest); // Start by performing self test and reporting values
        SEGGER_RTT_printf(0, "x-axis self test: acceleration trim within : %d % of factory value\n", toInt(SelfTest[0]));  
        SEGGER_RTT_printf(0, "y-axis self test: acceleration trim within : %d % of factory value\n", toInt(SelfTest[1]));  
        SEGGER_RTT_printf(0, "z-axis self test: acceleration trim within : %d % of factory value\n", toInt(SelfTest[2]));  
        SEGGER_RTT_printf(0, "x-axis self test: gyration trim within : %d % of factory value\n", toInt(SelfTest[3]));  
        SEGGER_RTT_printf(0, "y-axis self test: gyration trim within : %d % of factory value\n", toInt(SelfTest[4]));  
        SEGGER_RTT_printf(0, "z-axis self test: gyration trim within : %d % of factory value\n\n", toInt(SelfTest[5]));
        
        mpu9250.calibrateMPU9250(gyroBias, accelBias); // Calibrate gyro and accelerometers, load biases in bias registers  
        SEGGER_RTT_printf(0, "x gyro bias = %d\n", toInt(gyroBias[0]));
        SEGGER_RTT_printf(0, "y gyro bias = %d\n", toInt(gyroBias[1]));
        SEGGER_RTT_printf(0, "z gyro bias = %d\n", toInt(gyroBias[2]));
        SEGGER_RTT_printf(0, "x accel bias = %d\n", toInt(accelBias[0]));
        SEGGER_RTT_printf(0, "y accel bias = %d\n", toInt(accelBias[1]));
        SEGGER_RTT_printf(0, "z accel bias = %d\n\n", toInt(accelBias[2]));
        wait(2);
        
        mpu9250.initMPU9250(); 
        SEGGER_RTT_WriteString(0, "MPU9250 initialized for active data mode....\n"); // Initialize device for active mode read of acclerometer, gyroscope, and temperature
        mpu9250.initAK8963(magCalibration);
        SEGGER_RTT_WriteString(0, "AK8963 initialized for active data mode....\n"); // Initialize device for active mode read of magnetometer
        SEGGER_RTT_printf(0, "Accelerometer full-scale range = %d  g\n", toInt(2.0f*(float)(1<<Ascale)));
        SEGGER_RTT_printf(0, "Gyroscope full-scale range = %d  deg/s\n", toInt(250.0f*(float)(1<<Gscale)));
        if(Mscale == 0) SEGGER_RTT_WriteString(0, "Magnetometer resolution = 14  bits\n");
        if(Mscale == 1) SEGGER_RTT_WriteString(0, "Magnetometer resolution = 16  bits\n");
        if(Mmode == 2) SEGGER_RTT_WriteString(0, "Magnetometer ODR = 8 Hz\n");
        if(Mmode == 6) SEGGER_RTT_WriteString(0, "Magnetometer ODR = 100 Hz\n");
        SEGGER_RTT_WriteString(0, "\n");
        wait(1);
    }
    else {
        SEGGER_RTT_printf(0, "Could not connect to MPU9250: 0x%x \n",  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
    SEGGER_RTT_printf(0, "Accelerometer sensitivity is %d LSB/g \n", toInt(1.0f/aRes));
    SEGGER_RTT_printf(0, "Gyroscope sensitivity is %d LSB/deg/s \n", toInt(1.0f/gRes));
    SEGGER_RTT_printf(0, "Magnetometer sensitivity is %d LSB/G \n", toInt(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 1 s rate independent of data rates
        delt_t = t.read_ms() - count;
        if (delt_t > 1000) // update print once per second independent of read rate
        {
            SEGGER_RTT_printf(0, "\n\nax = %d", toInt(1000*ax)); 
            SEGGER_RTT_printf(0, " ay = %d", toInt(1000*ay)); 
            SEGGER_RTT_printf(0, " az = %d  mg\n", toInt(1000*az)); 
        
            SEGGER_RTT_printf(0, "gx = %d", toInt(gx)); 
            SEGGER_RTT_printf(0, " gy = %d", toInt(gy)); 
            SEGGER_RTT_printf(0, " gz = %d  deg/s\n", toInt(gz)); 
            
            SEGGER_RTT_printf(0, "mx = %d", toInt(mx)); 
            SEGGER_RTT_printf(0, " my = %d", toInt(my)); 
            SEGGER_RTT_printf(0, " mz = %d  mG\n", toInt(mz)); 
            
            tempCount = mpu9250.readTempData();  // Read the adc values
            temperature = ((float) tempCount) / 333.87f + 21.0f; // Temperature in degrees Celsius
            SEGGER_RTT_printf(0, "Temperature = %d  C\n\n", toInt(temperature)); 
            
            //SEGGER_RTT_printf(0, "q0 = %d\n", toInt(q[0]*100));
            //SEGGER_RTT_printf(0, "q1 = %d\n", toInt(q[1]*100));
            //SEGGER_RTT_printf(0, "q2 = %d\n", toInt(q[2]*100));
            //SEGGER_RTT_printf(0, "q3 = %d\n", toInt(q[3]*100));
        
            // 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   -= 1.05f; // Declination at Delft is 1 degrees 3 minutes on 2018-02-16
            roll  *= 180.0f / PI;
        
            SEGGER_RTT_printf(0, "Yaw: %d   Pitch: %d   Roll: %d\n\n", toInt(yaw), toInt(pitch), toInt(roll));
            //SEGGER_RTT_printf(0, "average rate = %d\n\n\n", toInt((float) sumCount/sum));
        
            count = t.read_ms();
            SEGGER_RTT_printf(0, "Time active: %d minutes\n---------------------------------", getTime(count));
        
            if(count > 1<<21)
            {
                t.start(); // start the timer over again if ~30 minutes has passed
                count = 0;
                deltat= 0;
                lastUpdate = t.read_us();
                shift = (++cycle * 34.9525f);
            }
            sum = 0;
            sumCount = 0; 
        }
    } 
}