Confusing Timing Results

[mjs513]

Hi Kris. I was running some timing tests using your Basic_AHRS sketch, but just using wire and comparing it the results on a imrtx1050. Using the sketch on the Arduino as is (read the interrupt status pin) I got the following results:

setclock(400000):
T3.5           6,365.16 Hz 
1050           8,117.8 Hz 
setclock(1000000):
T3.5           14,388.33 Hz
1050           22,005.26 Hz

In a post(https://forum.pjrc.com/threads/40343-MPU9250-Add-On-for-Teensy-3-6) that manitou pointed me too, over on the prjc forum it looked like you were getting better performance using a hard interrupt (using the interrupt pin for data ready). I just tried to that with your sketch by modifying the attachinterrupt code to read:

   //writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22); 
   writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x12);
   writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt

I think those are the right settings, just not sure why you are doing that using register 0x37 and not 0x58, but that is another question. Anyway back to the question when I did that and set up the interrupt I got some strange timing results:

400K = 1695.43 Hz
1000K = rate = 3333.60 Hz

Dramatic drop in performance. I must be doing something wrong but just not sure what. On the mbed side for the imrtx1050 have to figure out how their interrupts work :) but that's next.

Any thoughts on what I messed up?

[kriswiner]

Not sure. I would need to see your code.

0x58 is in the middle of the external sensor data array, not sure what this has to do with MPU9250 interrupt.

Normally I see a speed up with the interrupt versus polling. Except when polling you might be running the fusion filter whether you get new data or not. What I usually do is something like this:

if (new data)

read data

for some number of iterations run the Madgwick filter endfor

endif

get fusion rate

Usually 10 or 20 iterations is enough. On the STM32L4 I usually get fusion rate of 2 kHz or 4 kHz with 10 iterations.

So it depends on the structure of your loop.

Interestingly, running with the ESP32 probably about how you are doing it (but with a hard interrupt) I am seeing 20 kHz, way to high of course, but interesting in comparison.

On Tue, Nov 13, 2018 at 9:46 AM Mike S notifications@github.com wrote:

Hi Kris. I was running some timing tests using your Basic_AHRS sketch, but just using wire and comparing it the results on a imrtx1050. Using the sketch on the Arduino as is (read the interrupt status pin) I got the following results:

setclock(400000): T3.5 6,365.16 Hz 1050 8,117.8 Hz setclock(1000000): T3.5 14,388.33 Hz 1050 22,005.26 Hz

In a post( https://forum.pjrc.com/threads/40343-MPU9250-Add-On-for-Teensy-3-6) that manitou pointed me too, over on the prjc forum it looked like you were getting better performance using a hard interrupt (using the interrupt pin for data ready). I just tried to that with your sketch by modifying the attachinterrupt code to read:

//writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22); writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x12); writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01); // Enable data ready (bit 0) interrupt

I think those are the right settings, just not sure why you are doing that using register 0x37 and not 0x58, but that is another question. Anyway back to the question when I did that and set up the interrupt I got some strange timing results:

400K = 1695.43 Hz 1000K = rate = 3333.60 Hz

Dramatic drop in performance. I must be doing something wrong but just not sure what. On the mbed side for the imrtx1050 have to figure out how their interrupts work :) but that's next.

Any thoughts on what I messed up?

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[mjs513]

Thanks for getting back to me - here is the sketch that I am running. Basically your sketch with modification for newData unless I messed something up somewhere with the interrupt: Oh, think i forgot, the strange timing results are on the T3.5 running wire. Just wanted to be consisted when I did the comparisons.

/* 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.

 SDA and SCL should have external pull-up resistors (to 3.3V).
 10k resistors are on the EMSENSR-9250 breakout board.

 Hardware setup:
 MPU9250 Breakout --------- Arduino
 VDD ---------------------- 3.3V
 VDDI --------------------- 3.3V
 SDA ----------------------- A4
 SCL ----------------------- A5
 GND ---------------------- GND

 Note: The MPU9250 is an I2C sensor and uses the Arduino Wire library. 
 Because the sensor is not 5V tolerant, we are using a 3.3 V 8 MHz Pro Mini or a 3.3 V Teensy 3.1.
 We have disabled the internal pull-ups used by the Wire library in the Wire.h/twi.c utility file.
 We are also using the 400 kHz fast I2C mode by setting the TWI_FREQ  to 400000L /twi.h utility file.
 */
#include "Wire.h"   
//#include <i2c_t3.h>

// See also MPU-9250 Register Map and Descriptions, Revision 4.0, RM-MPU-9250A-00, Rev. 1.4, 9/9/2013 for registers not listed in 
// above document; the MPU9250 and MPU9150 are virtually identical but the latter has a different register map
//
//Magnetometer Registers
#define AK8963_ADDRESS   0x0C
#define AK8963_WHO_AM_I  0x00 // should return 0x48
#define AK8963_INFO      0x01
#define AK8963_ST1       0x02  // data ready status bit 0
#define AK8963_XOUT_L   0x03  // data
#define AK8963_XOUT_H  0x04
#define AK8963_YOUT_L  0x05
#define AK8963_YOUT_H  0x06
#define AK8963_ZOUT_L  0x07
#define AK8963_ZOUT_H  0x08
#define AK8963_ST2       0x09  // Data overflow bit 3 and data read error status bit 2
#define AK8963_CNTL      0x0A  // Power down (0000), single-measurement (0001), self-test (1000) and Fuse ROM (1111) modes on bits 3:0
#define AK8963_ASTC      0x0C  // Self test control
#define AK8963_I2CDIS    0x0F  // I2C disable
#define AK8963_ASAX      0x10  // Fuse ROM x-axis sensitivity adjustment value
#define AK8963_ASAY      0x11  // Fuse ROM y-axis sensitivity adjustment value
#define AK8963_ASAZ      0x12  // Fuse ROM z-axis sensitivity adjustment value

#define SELF_TEST_X_GYRO 0x00                  
#define SELF_TEST_Y_GYRO 0x01                                                                          
#define SELF_TEST_Z_GYRO 0x02

/*#define X_FINE_GAIN      0x03 // [7:0] fine gain
#define Y_FINE_GAIN      0x04
#define Z_FINE_GAIN      0x05
#define XA_OFFSET_H      0x06 // User-defined trim values for accelerometer
#define XA_OFFSET_L_TC   0x07
#define YA_OFFSET_H      0x08
#define YA_OFFSET_L_TC   0x09
#define ZA_OFFSET_H      0x0A
#define ZA_OFFSET_L_TC   0x0B */

#define SELF_TEST_X_ACCEL 0x0D
#define SELF_TEST_Y_ACCEL 0x0E    
#define SELF_TEST_Z_ACCEL 0x0F

#define SELF_TEST_A      0x10

#define XG_OFFSET_H      0x13  // User-defined trim values for gyroscope
#define XG_OFFSET_L      0x14
#define YG_OFFSET_H      0x15
#define YG_OFFSET_L      0x16
#define ZG_OFFSET_H      0x17
#define ZG_OFFSET_L      0x18
#define SMPLRT_DIV       0x19
#define CONFIG           0x1A
#define GYRO_CONFIG      0x1B
#define ACCEL_CONFIG     0x1C
#define ACCEL_CONFIG2    0x1D
#define LP_ACCEL_ODR     0x1E   
#define WOM_THR          0x1F   

#define MOT_DUR          0x20  // Duration counter threshold for motion interrupt generation, 1 kHz rate, LSB = 1 ms
#define ZMOT_THR         0x21  // Zero-motion detection threshold bits [7:0]
#define ZRMOT_DUR        0x22  // Duration counter threshold for zero motion interrupt generation, 16 Hz rate, LSB = 64 ms

#define FIFO_EN          0x23
#define I2C_MST_CTRL     0x24   
#define I2C_SLV0_ADDR    0x25
#define I2C_SLV0_REG     0x26
#define I2C_SLV0_CTRL    0x27
#define I2C_SLV1_ADDR    0x28
#define I2C_SLV1_REG     0x29
#define I2C_SLV1_CTRL    0x2A
#define I2C_SLV2_ADDR    0x2B
#define I2C_SLV2_REG     0x2C
#define I2C_SLV2_CTRL    0x2D
#define I2C_SLV3_ADDR    0x2E
#define I2C_SLV3_REG     0x2F
#define I2C_SLV3_CTRL    0x30
#define I2C_SLV4_ADDR    0x31
#define I2C_SLV4_REG     0x32
#define I2C_SLV4_DO      0x33
#define I2C_SLV4_CTRL    0x34
#define I2C_SLV4_DI      0x35
#define I2C_MST_STATUS   0x36
#define INT_PIN_CFG      0x37
#define INT_ENABLE       0x38
#define DMP_INT_STATUS   0x39  // Check DMP interrupt
#define INT_STATUS       0x3A
#define ACCEL_XOUT_H     0x3B
#define ACCEL_XOUT_L     0x3C
#define ACCEL_YOUT_H     0x3D
#define ACCEL_YOUT_L     0x3E
#define ACCEL_ZOUT_H     0x3F
#define ACCEL_ZOUT_L     0x40
#define TEMP_OUT_H       0x41
#define TEMP_OUT_L       0x42
#define GYRO_XOUT_H      0x43
#define GYRO_XOUT_L      0x44
#define GYRO_YOUT_H      0x45
#define GYRO_YOUT_L      0x46
#define GYRO_ZOUT_H      0x47
#define GYRO_ZOUT_L      0x48
#define EXT_SENS_DATA_00 0x49
#define EXT_SENS_DATA_01 0x4A
#define EXT_SENS_DATA_02 0x4B
#define EXT_SENS_DATA_03 0x4C
#define EXT_SENS_DATA_04 0x4D
#define EXT_SENS_DATA_05 0x4E
#define EXT_SENS_DATA_06 0x4F
#define EXT_SENS_DATA_07 0x50
#define EXT_SENS_DATA_08 0x51
#define EXT_SENS_DATA_09 0x52
#define EXT_SENS_DATA_10 0x53
#define EXT_SENS_DATA_11 0x54
#define EXT_SENS_DATA_12 0x55
#define EXT_SENS_DATA_13 0x56
#define EXT_SENS_DATA_14 0x57
#define EXT_SENS_DATA_15 0x58
#define EXT_SENS_DATA_16 0x59
#define EXT_SENS_DATA_17 0x5A
#define EXT_SENS_DATA_18 0x5B
#define EXT_SENS_DATA_19 0x5C
#define EXT_SENS_DATA_20 0x5D
#define EXT_SENS_DATA_21 0x5E
#define EXT_SENS_DATA_22 0x5F
#define EXT_SENS_DATA_23 0x60
#define MOT_DETECT_STATUS 0x61
#define I2C_SLV0_DO      0x63
#define I2C_SLV1_DO      0x64
#define I2C_SLV2_DO      0x65
#define I2C_SLV3_DO      0x66
#define I2C_MST_DELAY_CTRL 0x67
#define SIGNAL_PATH_RESET  0x68
#define MOT_DETECT_CTRL  0x69
#define USER_CTRL        0x6A  // Bit 7 enable DMP, bit 3 reset DMP
#define PWR_MGMT_1       0x6B // Device defaults to the SLEEP mode
#define PWR_MGMT_2       0x6C
#define DMP_BANK         0x6D  // Activates a specific bank in the DMP
#define DMP_RW_PNT       0x6E  // Set read/write pointer to a specific start address in specified DMP bank
#define DMP_REG          0x6F  // Register in DMP from which to read or to which to write
#define DMP_REG_1        0x70
#define DMP_REG_2        0x71 
#define FIFO_COUNTH      0x72
#define FIFO_COUNTL      0x73
#define FIFO_R_W         0x74
#define WHO_AM_I_MPU9250 0x75 // Should return 0x71
#define XA_OFFSET_H      0x77
#define XA_OFFSET_L      0x78
#define YA_OFFSET_H      0x7A
#define YA_OFFSET_L      0x7B
#define ZA_OFFSET_H      0x7D
#define ZA_OFFSET_L      0x7E

// Using the MSENSR-9250 breakout board, ADO is set to 0 
// Seven-bit device address is 110100 for ADO = 0 and 110101 for ADO = 1
//#define ADO 0

#define MPU9250_ADDRESS 0x68  // Device address when ADO = 0

#define AHRS true         // set to false for basic data read
#define SerialDebug true   // set to true to get Serial output for debugging

// Set initial input parameters
enum Ascale {
  AFS_2G = 0,
  AFS_4G,
  AFS_8G,
  AFS_16G
};

enum Gscale {
  GFS_250DPS = 0,
  GFS_500DPS,
  GFS_1000DPS,
  GFS_2000DPS
};

enum Mscale {
  MFS_14BITS = 0, // 0.6 mG per LSB
  MFS_16BITS      // 0.15 mG per LSB
};

// Specify sensor full scale
uint8_t Gscale = GFS_250DPS;
uint8_t Ascale = AFS_2G;
uint8_t Mscale = MFS_16BITS; // Choose either 14-bit or 16-bit magnetometer resolution
uint8_t Mmode = 0x02;        // 2 for 8 Hz, 6 for 100 Hz continuous magnetometer data read
float aRes, gRes, mRes;      // scale resolutions per LSB for the sensors

// Pin definitions
int intPin = 1;  // These can be changed, 2 and 3 are the Arduinos ext int pins
int myLed = 13;

int16_t accelCount[3];  // Stores the 16-bit signed accelerometer sensor output
int16_t gyroCount[3];   // Stores the 16-bit signed gyro sensor output
int16_t magCount[3];    // Stores the 16-bit signed magnetometer sensor output
float magCalibration[3] = {0, 0, 0}, magbias[3] = {0, 0, 0};  // Factory mag calibration and mag bias
float gyroBias[3] = {0, 0, 0}, accelBias[3] = {0, 0, 0};      // Bias corrections for gyro and accelerometer
int16_t tempCount;      // temperature raw count output
float   temperature;    // Stores the real internal chip temperature in degrees Celsius
float   SelfTest[6];    // holds results of gyro and accelerometer self test

// global constants for 9 DoF fusion and AHRS (Attitude and Heading Reference System)
float GyroMeasError = PI * (40.0f / 180.0f);   // gyroscope measurement error in rads/s (start at 40 deg/s)
float GyroMeasDrift = PI * (0.0f  / 180.0f);   // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s)
// There is a tradeoff in the beta parameter between accuracy and response speed.
// In the original Madgwick study, beta of 0.041 (corresponding to GyroMeasError of 2.7 degrees/s) was found to give optimal accuracy.
// However, with this value, the LSM9SD0 response time is about 10 seconds to a stable initial quaternion.
// Subsequent changes also require a longish lag time to a stable output, not fast enough for a quadcopter or robot car!
// By increasing beta (GyroMeasError) by about a factor of fifteen, the response time constant is reduced to ~2 sec
// I haven't noticed any reduction in solution accuracy. This is essentially the I coefficient in a PID control sense; 
// the bigger the feedback coefficient, the faster the solution converges, usually at the expense of accuracy. 
// In any case, this is the free parameter in the Madgwick filtering and fusion scheme.
float beta = sqrt(3.0f / 4.0f) * GyroMeasError;   // compute beta
float zeta = sqrt(3.0f / 4.0f) * GyroMeasDrift;   // compute zeta, the other free parameter in the Madgwick scheme usually set to a small or zero value
#define Kp 2.0f * 5.0f // these are the free parameters in the Mahony filter and fusion scheme, Kp for proportional feedback, Ki for integral
#define Ki 0.0f

uint32_t delt_t = 0; // used to control display output rate
uint32_t count = 0, sumCount = 0; // used to control display output rate
float pitch, yaw, roll;
float deltat = 0.0f, sum = 0.0f;        // integration interval for both filter schemes
uint32_t lastUpdate = 0, firstUpdate = 0; // used to calculate integration interval
uint32_t Now = 0;        // used to calculate integration interval

float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values 
float q[4] = {1.0f, 0.0f, 0.0f, 0.0f};    // vector to hold quaternion
float eInt[3] = {0.0f, 0.0f, 0.0f};       // vector to hold integral error for Mahony method

uint8_t newData = 0;

void setup()
{
  Wire.begin();
//  TWBR = 12;  // 400 kbit/sec I2C speed
  // Setup for Master mode, pins 18/19, external pullups, 400kHz
  Wire.setClock(400000);
  Serial.begin(115200);
  delay(2000);

  // Set up the interrupt pin, its set as active high, push-pull

  pinMode(myLed, OUTPUT);
  digitalWrite(myLed, HIGH);
  delay(1000);

  // Read the WHO_AM_I register, this is a good test of communication
  byte c = readByte(MPU9250_ADDRESS, WHO_AM_I_MPU9250);  // Read WHO_AM_I register for MPU-9250
  Serial.print("MPU9250 "); Serial.print("I AM "); Serial.print(c, HEX); Serial.print(" I should be "); Serial.println(0x71, HEX);
  delay(5000); 

  if (c == 0x71) // WHO_AM_I should always be 0x68
  {  
    Serial.println("MPU9250 is online...");

    MPU9250SelfTest(SelfTest); // Start by performing self test and reporting values
    Serial.print("x-axis self test: acceleration trim within : "); Serial.print(SelfTest[0],1); Serial.println("% of factory value");
    Serial.print("y-axis self test: acceleration trim within : "); Serial.print(SelfTest[1],1); Serial.println("% of factory value");
    Serial.print("z-axis self test: acceleration trim within : "); Serial.print(SelfTest[2],1); Serial.println("% of factory value");
    Serial.print("x-axis self test: gyration trim within : "); Serial.print(SelfTest[3],1); Serial.println("% of factory value");
    Serial.print("y-axis self test: gyration trim within : "); Serial.print(SelfTest[4],1); Serial.println("% of factory value");
    Serial.print("z-axis self test: gyration trim within : "); Serial.print(SelfTest[5],1); Serial.println("% of factory value");
    delay(5000);

  calibrateMPU9250(gyroBias, accelBias); // Calibrate gyro and accelerometers, load biases in bias registers

  delay(1000); 

  initMPU9250(); 
  Serial.println("MPU9250 initialized for active data mode...."); // Initialize device for active mode read of acclerometer, gyroscope, and temperature

  // Read the WHO_AM_I register of the magnetometer, this is a good test of communication
  byte d = readByte(AK8963_ADDRESS, AK8963_WHO_AM_I);  // Read WHO_AM_I register for AK8963
  Serial.print("AK8963 "); Serial.print("I AM "); Serial.print(d, HEX); Serial.print(" I should be "); Serial.println(0x48, HEX);

  delay(1000); 

  // Get magnetometer calibration from AK8963 ROM
  initAK8963(magCalibration); Serial.println("AK8963 initialized for active data mode...."); // Initialize device for active mode read of magnetometer

  if(SerialDebug) {
//  Serial.println("Calibration values: ");
  Serial.print("X-Axis sensitivity adjustment value "); Serial.println(magCalibration[0], 2);
  Serial.print("Y-Axis sensitivity adjustment value "); Serial.println(magCalibration[1], 2);
  Serial.print("Z-Axis sensitivity adjustment value "); Serial.println(magCalibration[2], 2);
  }

  delay(1000);  
  }
  else
  {
    Serial.print("Could not connect to MPU9250: 0x");
    Serial.println(c, HEX);
    while(1) ; // Loop forever if communication doesn't happen
  }

  // attaching the interrupt to microcontroller pin
  pinMode(intPin,INPUT);
  attachInterrupt(intPin,drdy_isr,RISING);

}

void drdy_isr(){
  newData = 1;
}

void loop()
{  
  // If intPin goes high, all data registers have new data
  //if (readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01) {  // On interrupt, check if data ready interrupt
  if(newData == 1) {
    newData == 0;
    readAccelData(accelCount);  // Read the x/y/z adc values
    getAres();

    // 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];  

    readGyroData(gyroCount);  // Read the x/y/z adc values
    getGres();

    // Calculate the gyro value into actual degrees per second
    gx = (float)gyroCount[0]*gRes;  // get actual gyro value, this depends on scale being set
    gy = (float)gyroCount[1]*gRes;  
    gz = (float)gyroCount[2]*gRes;   

    //newMagData = (readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01);
    //if(newMagData == true) { // wait for magnetometer data ready bit to be set
    readMagData(magCount);  // Read the x/y/z adc values
    getMres();
    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

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

  sum += deltat; // sum for averaging filter update rate
  sumCount++;

  // Sensors x (y)-axis of the accelerometer is aligned with the y (x)-axis of the magnetometer;
  // the magnetometer z-axis (+ down) is opposite to z-axis (+ up) of accelerometer and gyro!
  // We have to make some allowance for this orientationmismatch in feeding the output to the quaternion filter.
  // For the MPU-9250, we have chosen a magnetic rotation that keeps the sensor forward along the x-axis just like
  // in the LSM9DS0 sensor. This rotation can be modified to allow any convenient orientation convention.
  // This is ok by aircraft orientation standards!  
  // Pass gyro rate as rad/s
  MadgwickQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f,  my,  mx, mz);
//  MahonyQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f, my, mx, mz);

    if (!AHRS) {
    delt_t = millis() - count;
    if(delt_t > 500) {

    if(SerialDebug) {
    // Print acceleration values in milligs!
    Serial.print("X-acceleration: "); Serial.print(1000*ax); Serial.print(" mg ");
    Serial.print("Y-acceleration: "); Serial.print(1000*ay); Serial.print(" mg ");
    Serial.print("Z-acceleration: "); Serial.print(1000*az); Serial.println(" mg ");

    // Print gyro values in degree/sec
    Serial.print("X-gyro rate: "); Serial.print(gx, 3); Serial.print(" degrees/sec "); 
    Serial.print("Y-gyro rate: "); Serial.print(gy, 3); Serial.print(" degrees/sec "); 
    Serial.print("Z-gyro rate: "); Serial.print(gz, 3); Serial.println(" degrees/sec"); 

    // Print mag values in degree/sec
    Serial.print("X-mag field: "); Serial.print(mx); Serial.print(" mG "); 
    Serial.print("Y-mag field: "); Serial.print(my); Serial.print(" mG "); 
    Serial.print("Z-mag field: "); Serial.print(mz); Serial.println(" mG"); 

    tempCount = readTempData();  // Read the adc values
    temperature = ((float) tempCount) / 333.87 + 21.0; // Temperature in degrees Centigrade
   // Print temperature in degrees Centigrade      
    Serial.print("Temperature is ");  Serial.print(temperature, 1);  Serial.println(" degrees C"); // Print T values to tenths of s degree C
    }

    count = millis();
    }
    }
    else {

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

    if(SerialDebug) {
    Serial.print("ax = "); Serial.print((int)1000*ax);  
    Serial.print(" ay = "); Serial.print((int)1000*ay); 
    Serial.print(" az = "); Serial.print((int)1000*az); Serial.println(" mg");
    Serial.print("gx = "); Serial.print( gx, 2); 
    Serial.print(" gy = "); Serial.print( gy, 2); 
    Serial.print(" gz = "); Serial.print( gz, 2); Serial.println(" deg/s");
    Serial.print("mx = "); Serial.print( (int)mx ); 
    Serial.print(" my = "); Serial.print( (int)my ); 
    Serial.print(" mz = "); Serial.print( (int)mz ); Serial.println(" mG");

    Serial.print("q0 = "); Serial.print(q[0]);
    Serial.print(" qx = "); Serial.print(q[1]); 
    Serial.print(" qy = "); Serial.print(q[2]); 
    Serial.print(" qz = "); Serial.println(q[3]); 
    }               

  // 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   -= 13.8; // Declination at Danville, California is 13 degrees 48 minutes and 47 seconds on 2014-04-04
    roll  *= 180.0f / PI;

    if(SerialDebug) {
    Serial.print("Yaw, Pitch, Roll: ");
    Serial.print(yaw, 2);
    Serial.print(", ");
    Serial.print(pitch, 2);
    Serial.print(", ");
    Serial.println(roll, 2);

    Serial.print("rate = "); Serial.print((float)sumCount/sum, 2); Serial.println(" Hz");
    }

    // With these settings the filter is updating at a ~145 Hz rate using the Madgwick scheme and 
    // >200 Hz using the Mahony scheme even though the display refreshes at only 2 Hz.
    // The filter update rate is determined mostly by the mathematical steps in the respective algorithms, 
    // the processor speed (8 MHz for the 3.3V Pro Mini), and the magnetometer ODR:
    // an ODR of 10 Hz for the magnetometer produce the above rates, maximum magnetometer ODR of 100 Hz produces
    // filter update rates of 36 - 145 and ~38 Hz for the Madgwick and Mahony schemes, respectively. 
    // This is presumably because the magnetometer read takes longer than the gyro or accelerometer reads.
    // This filter update rate should be fast enough to maintain accurate platform orientation for 
    // stabilization control of a fast-moving robot or quadcopter. Compare to the update rate of 200 Hz
    // produced by the on-board Digital Motion Processor of Invensense's MPU6050 6 DoF and MPU9150 9DoF sensors.
    // The 3.3 V 8 MHz Pro Mini is doing pretty well!
    //display.setCursor(0, 40); display.print("rt: "); display.print((float) sumCount / sum, 2); display.print(" Hz"); 
    //display.display();

    digitalWrite(myLed, !digitalRead(myLed));
    count = millis(); 
    sumCount = 0;
    sum = 0;    
    }
    }

}

//===================================================================================================================
//====== Set of useful function to access acceleration. gyroscope, magnetometer, and temperature data
//===================================================================================================================

void getMres() {
  switch (Mscale)
  {
  // Possible magnetometer scales (and their register bit settings) are:
  // 14 bit resolution (0) and 16 bit resolution (1)
    case MFS_14BITS:
          mRes = 10.*4912./8190.; // Proper scale to return milliGauss
          break;
    case MFS_16BITS:
          mRes = 10.*4912./32760.0; // Proper scale to return milliGauss
          break;
  }
}

void getGres() {
  switch (Gscale)
  {
  // Possible gyro scales (and their register bit settings) are:
  // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS  (11). 
        // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
    case GFS_250DPS:
          gRes = 250.0/32768.0;
          break;
    case GFS_500DPS:
          gRes = 500.0/32768.0;
          break;
    case GFS_1000DPS:
          gRes = 1000.0/32768.0;
          break;
    case GFS_2000DPS:
          gRes = 2000.0/32768.0;
          break;
  }
}

void getAres() {
  switch (Ascale)
  {
  // Possible accelerometer scales (and their register bit settings) are:
  // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs  (11). 
        // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
    case AFS_2G:
          aRes = 2.0/32768.0;
          break;
    case AFS_4G:
          aRes = 4.0/32768.0;
          break;
    case AFS_8G:
          aRes = 8.0/32768.0;
          break;
    case AFS_16G:
          aRes = 16.0/32768.0;
          break;
  }
}

void readAccelData(int16_t * destination)
{
  uint8_t rawData[6];  // x/y/z accel register data stored here
  readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
  destination[0] = ((int16_t)rawData[0] << 8) | rawData[1] ;  // Turn the MSB and LSB into a signed 16-bit value
  destination[1] = ((int16_t)rawData[2] << 8) | rawData[3] ;  
  destination[2] = ((int16_t)rawData[4] << 8) | rawData[5] ; 
}

void readGyroData(int16_t * destination)
{
  uint8_t rawData[6];  // x/y/z gyro register data stored here
  readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
  destination[0] = ((int16_t)rawData[0] << 8) | rawData[1] ;  // Turn the MSB and LSB into a signed 16-bit value
  destination[1] = ((int16_t)rawData[2] << 8) | rawData[3] ;  
  destination[2] = ((int16_t)rawData[4] << 8) | rawData[5] ; 
}

void readMagData(int16_t * destination)
{
  uint8_t rawData[7];  // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition
  if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set
  readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]);  // Read the six raw data and ST2 registers sequentially into data array
  uint8_t c = rawData[6]; // End data read by reading ST2 register
    if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data
    destination[0] = ((int16_t)rawData[1] << 8) | rawData[0] ;  // Turn the MSB and LSB into a signed 16-bit value
    destination[1] = ((int16_t)rawData[3] << 8) | rawData[2] ;  // Data stored as little Endian
    destination[2] = ((int16_t)rawData[5] << 8) | rawData[4] ; 
   }
  }
}

int16_t readTempData()
{
  uint8_t rawData[2];  // x/y/z gyro register data stored here
  readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]);  // Read the two raw data registers sequentially into data array 
  return ((int16_t)rawData[0] << 8) | rawData[1] ;  // Turn the MSB and LSB into a 16-bit value
}

void initAK8963(float * destination)
{
  // First extract the factory calibration for each magnetometer axis
  uint8_t rawData[3];  // x/y/z gyro calibration data stored here
  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
  delay(10);
  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode
  delay(10);
  readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
  destination[0] =  (float)(rawData[0] - 128)/256. + 1.;   // Return x-axis sensitivity adjustment values, etc.
  destination[1] =  (float)(rawData[1] - 128)/256. + 1.;  
  destination[2] =  (float)(rawData[2] - 128)/256. + 1.; 
  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
  delay(10);
  // Configure the magnetometer for continuous read and highest resolution
  // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register,
  // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates
  writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR
  delay(10);
}

void initMPU9250()
{  
 // wake up device
  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors 
  delay(100); // Wait for all registers to reset 

 // get stable time source
  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  // Auto select clock source to be PLL gyroscope reference if ready else
  delay(200); 

 // Configure Gyro and Thermometer
 // Disable FSYNC and set thermometer and gyro bandwidth to 41 and 42 Hz, respectively; 
 // minimum delay time for this setting is 5.9 ms, which means sensor fusion update rates cannot
 // be higher than 1 / 0.0059 = 170 Hz
 // DLPF_CFG = bits 2:0 = 011; this limits the sample rate to 1000 Hz for both
 // With the MPU9250, it is possible to get gyro sample rates of 32 kHz (!), 8 kHz, or 1 kHz
  writeByte(MPU9250_ADDRESS, CONFIG, 0x03);  

 // Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV)
  writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04);  // Use a 200 Hz rate; a rate consistent with the filter update rate 
                                    // determined inset in CONFIG above

// Set gyroscope full scale range
 // Range selects FS_SEL and GFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
  uint8_t c = readByte(MPU9250_ADDRESS, GYRO_CONFIG); // get current GYRO_CONFIG register value
 // c = c & ~0xE0; // Clear self-test bits [7:5] 
  c = c & ~0x03; // Clear Fchoice bits [1:0] 
  c = c & ~0x18; // Clear GFS bits [4:3]
  c = c | Gscale << 3; // Set full scale range for the gyro
 // c =| 0x00; // Set Fchoice for the gyro to 11 by writing its inverse to bits 1:0 of GYRO_CONFIG
  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c ); // Write new GYRO_CONFIG value to register

 // Set accelerometer full-scale range configuration
  c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG); // get current ACCEL_CONFIG register value
 // c = c & ~0xE0; // Clear self-test bits [7:5] 
  c = c & ~0x18;  // Clear AFS bits [4:3]
  c = c | Ascale << 3; // Set full scale range for the accelerometer 
  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c); // Write new ACCEL_CONFIG register value

 // Set accelerometer sample rate configuration
 // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for
 // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz
  c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2); // get current ACCEL_CONFIG2 register value
  c = c & ~0x0F; // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])  
  c = c | 0x03;  // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c); // Write new ACCEL_CONFIG2 register value

 // The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, 
 // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting

  // Configure Interrupts and Bypass Enable
  // Set interrupt pin active high, push-pull, hold interrupt pin level HIGH until interrupt cleared,
  // clear on read of INT_STATUS, and enable I2C_BYPASS_EN so additional chips 
  // can join the I2C bus and all can be controlled by the Arduino as master
   //writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22); 
   writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x12);
   writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
   delay(100);
}

// Function which accumulates gyro and accelerometer data after device initialization. It calculates the average
// of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers.
void calibrateMPU9250(float * dest1, float * dest2)
{  
  uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data
  uint16_t ii, packet_count, fifo_count;
  int32_t gyro_bias[3]  = {0, 0, 0}, accel_bias[3] = {0, 0, 0};

 // reset device
  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
  delay(100);

 // get stable time source; Auto select clock source to be PLL gyroscope reference if ready 
 // else use the internal oscillator, bits 2:0 = 001
  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  
  writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00);
  delay(200);                                    

// Configure device for bias calculation
  writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00);   // Disable all interrupts
  writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);      // Disable FIFO
  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00);   // Turn on internal clock source
  writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master
  writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00);    // Disable FIFO and I2C master modes
  writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C);    // Reset FIFO and DMP
  delay(15);

// Configure MPU6050 gyro and accelerometer for bias calculation
  writeByte(MPU9250_ADDRESS, CONFIG, 0x01);      // Set low-pass filter to 188 Hz
  writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00);  // Set sample rate to 1 kHz
  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);  // Set gyro full-scale to 250 degrees per second, maximum sensitivity
  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity

  uint16_t  gyrosensitivity  = 131;   // = 131 LSB/degrees/sec
  uint16_t  accelsensitivity = 16384;  // = 16384 LSB/g

    // Configure FIFO to capture accelerometer and gyro data for bias calculation
  writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40);   // Enable FIFO  
  writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78);     // Enable gyro and accelerometer sensors for FIFO  (max size 512 bytes in MPU-9150)
  delay(40); // accumulate 40 samples in 40 milliseconds = 480 bytes

// At end of sample accumulation, turn off FIFO sensor read
  writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);        // Disable gyro and accelerometer sensors for FIFO
  readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count
  fifo_count = ((uint16_t)data[0] << 8) | data[1];
  packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging

  for (ii = 0; ii < packet_count; ii++) {
    int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0};
    readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging
    accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1]  ) ;  // Form signed 16-bit integer for each sample in FIFO
    accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3]  ) ;
    accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5]  ) ;    
    gyro_temp[0]  = (int16_t) (((int16_t)data[6] << 8) | data[7]  ) ;
    gyro_temp[1]  = (int16_t) (((int16_t)data[8] << 8) | data[9]  ) ;
    gyro_temp[2]  = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;

    accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
    accel_bias[1] += (int32_t) accel_temp[1];
    accel_bias[2] += (int32_t) accel_temp[2];
    gyro_bias[0]  += (int32_t) gyro_temp[0];
    gyro_bias[1]  += (int32_t) gyro_temp[1];
    gyro_bias[2]  += (int32_t) gyro_temp[2];

}
    accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases
    accel_bias[1] /= (int32_t) packet_count;
    accel_bias[2] /= (int32_t) packet_count;
    gyro_bias[0]  /= (int32_t) packet_count;
    gyro_bias[1]  /= (int32_t) packet_count;
    gyro_bias[2]  /= (int32_t) packet_count;

  if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;}  // Remove gravity from the z-axis accelerometer bias calculation
  else {accel_bias[2] += (int32_t) accelsensitivity;}

// Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup
  data[0] = (-gyro_bias[0]/4  >> 8) & 0xFF; // Divide by 4 to get 32.9 LSB per deg/s to conform to expected bias input format
  data[1] = (-gyro_bias[0]/4)       & 0xFF; // Biases are additive, so change sign on calculated average gyro biases
  data[2] = (-gyro_bias[1]/4  >> 8) & 0xFF;
  data[3] = (-gyro_bias[1]/4)       & 0xFF;
  data[4] = (-gyro_bias[2]/4  >> 8) & 0xFF;
  data[5] = (-gyro_bias[2]/4)       & 0xFF;

// Push gyro biases to hardware registers
  writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]);
  writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]);
  writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]);
  writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]);
  writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]);
  writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);

// Output scaled gyro biases for display in the main program
  dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity;  
  dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity;
  dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;

// Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain
// factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold
// non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature
// compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that
// the accelerometer biases calculated above must be divided by 8.

  int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases
  readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values
  accel_bias_reg[0] = (int32_t) (((int16_t)data[0] << 8) | data[1]);
  readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]);
  accel_bias_reg[1] = (int32_t) (((int16_t)data[0] << 8) | data[1]);
  readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
  accel_bias_reg[2] = (int32_t) (((int16_t)data[0] << 8) | data[1]);

  uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers
  uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis

  for(ii = 0; ii < 3; ii++) {
    if((accel_bias_reg[ii] & mask)) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit
  }

  // Construct total accelerometer bias, including calculated average accelerometer bias from above
  accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale)
  accel_bias_reg[1] -= (accel_bias[1]/8);
  accel_bias_reg[2] -= (accel_bias[2]/8);

  data[0] = (accel_bias_reg[0] >> 8) & 0xFF;
  data[1] = (accel_bias_reg[0])      & 0xFF;
  data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers
  data[2] = (accel_bias_reg[1] >> 8) & 0xFF;
  data[3] = (accel_bias_reg[1])      & 0xFF;
  data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers
  data[4] = (accel_bias_reg[2] >> 8) & 0xFF;
  data[5] = (accel_bias_reg[2])      & 0xFF;
  data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers

// Apparently this is not working for the acceleration biases in the MPU-9250
// Are we handling the temperature correction bit properly?
// Push accelerometer biases to hardware registers
  writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]);
  writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]);
  writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]);
  writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]);
  writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]);
  writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);

// Output scaled accelerometer biases for display in the main program
   dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; 
   dest2[1] = (float)accel_bias[1]/(float)accelsensitivity;
   dest2[2] = (float)accel_bias[2]/(float)accelsensitivity;
}

// Accelerometer and gyroscope self test; check calibration wrt factory settings
void MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass
{
   uint8_t rawData[6] = {0, 0, 0, 0, 0, 0};
   uint8_t selfTest[6];
   int32_t gAvg[3] = {0}, aAvg[3] = {0}, aSTAvg[3] = {0}, gSTAvg[3] = {0};
   float factoryTrim[6];
   uint8_t FS = 0;

  writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00);    // Set gyro sample rate to 1 kHz
  writeByte(MPU9250_ADDRESS, CONFIG, 0x02);        // Set gyro sample rate to 1 kHz and DLPF to 92 Hz
  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, FS<<3);  // Set full scale range for the gyro to 250 dps
  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz
  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, FS<<3); // Set full scale range for the accelerometer to 2 g

  for( int ii = 0; ii < 200; ii++) {  // get average current values of gyro and acclerometer

  readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);        // Read the six raw data registers into data array
  aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
  aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
  aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 

    readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);       // Read the six raw data registers sequentially into data array
  gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
  gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
  gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
  }

  for (int ii =0; ii < 3; ii++) {  // Get average of 200 values and store as average current readings
  aAvg[ii] /= 200;
  gAvg[ii] /= 200;
  }

// Configure the accelerometer for self-test
   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g
   writeByte(MPU9250_ADDRESS, GYRO_CONFIG,  0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s
   delay(25);  // Delay a while to let the device stabilize

  for( int ii = 0; ii < 200; ii++) {  // get average self-test values of gyro and acclerometer

  readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
  aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
  aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
  aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 

    readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
  gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
  gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
  gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
  }

  for (int ii =0; ii < 3; ii++) {  // Get average of 200 values and store as average self-test readings
  aSTAvg[ii] /= 200;
  gSTAvg[ii] /= 200;
  }   

 // Configure the gyro and accelerometer for normal operation
   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00);  
   writeByte(MPU9250_ADDRESS, GYRO_CONFIG,  0x00);  
   delay(25);  // Delay a while to let the device stabilize

   // Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg
   selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results
   selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results
   selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results
   selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO);  // X-axis gyro self-test results
   selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO);  // Y-axis gyro self-test results
   selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO);  // Z-axis gyro self-test results

  // Retrieve factory self-test value from self-test code reads
   factoryTrim[0] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation
   factoryTrim[1] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation
   factoryTrim[2] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation
   factoryTrim[3] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation
   factoryTrim[4] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation
   factoryTrim[5] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation

 // Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response
 // To get percent, must multiply by 100
   for (int i = 0; i < 3; i++) {
     destination[i]   = 100.0*((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i] - 100.;   // Report percent differences
     destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3] - 100.; // Report percent differences
   }

}

// I2C read/write functions for the MPU9250 and AK8963 sensors

        void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
{
  Wire.beginTransmission(address);  // Initialize the Tx buffer
  Wire.write(subAddress);           // Put slave register address in Tx buffer
  Wire.write(data);                 // Put data in Tx buffer
  Wire.endTransmission();           // Send the Tx buffer
}

        uint8_t readByte(uint8_t address, uint8_t subAddress)
{
  uint8_t data; // `data` will store the register data   
  Wire.beginTransmission(address);         // Initialize the Tx buffer
  Wire.write(subAddress);                  // Put slave register address in Tx buffer
  Wire.endTransmission();        // Send the Tx buffer, but send a restart to keep connection alive
//  Wire.endTransmission(false);             // Send the Tx buffer, but send a restart to keep connection alive
//  Wire.requestFrom(address, 1);  // Read one byte from slave register address 
  Wire.requestFrom(address, (size_t) 1);   // Read one byte from slave register address 
  data = Wire.read();                      // Fill Rx buffer with result
  return data;                             // Return data read from slave register
}

        void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
{  
  Wire.beginTransmission(address);   // Initialize the Tx buffer
  Wire.write(subAddress);            // Put slave register address in Tx buffer
  Wire.endTransmission();  // Send the Tx buffer, but send a restart to keep connection alive
//  Wire.endTransmission(false);       // Send the Tx buffer, but send a restart to keep connection alive
  uint8_t i = 0;
//        Wire.requestFrom(address, count);  // Read bytes from slave register address 
        Wire.requestFrom(address, (size_t) count);  // Read bytes from slave register address 
  while (Wire.available()) {
        dest[i++] = Wire.read(); }         // Put read results in the Rx buffer
}

[kriswiner]

There are a lot of problems with this sketch. Not sure why you chose this one to play with.

First of all, the accel and gyro data should be read in one operation, the resolutions (gerAres(),eg) should be done in setup just once, the mag really ought to be run at 100 Hz, the mag biases are hard coded (obviously wrong for your sensor), the sensor data order into the Madgwick filter is wrong, etc. Not sure if these have anything to do with your timing results.

You might try changing PI to in-sketch defined pi = 3.14159f. This speeded up the fuson filter by 10x when I did this for the STM32L4.

In short, this is not a good vehicle for exploring timing issues. At a minimum I would limit the Madgwick fusion in a for loop to 10 iterations, correct some of the obvious sketch errors and try the timing test again.

On Tue, Nov 13, 2018 at 10:11 AM Mike S notifications@github.com wrote:

Thanks for getting back to me - here is the sketch that I am running. Basically your sketch with modification for newData unless I messed something up somewhere with the interrupt: Oh, think i forgot, the strange timing results are on the T3.5 running wire. Just wanted to be consisted when I did the comparisons.

/* 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.

SDA and SCL should have external pull-up resistors (to 3.3V). 10k resistors are on the EMSENSR-9250 breakout board.

Hardware setup: MPU9250 Breakout --------- Arduino VDD ---------------------- 3.3V VDDI --------------------- 3.3V SDA ----------------------- A4 SCL ----------------------- A5 GND ---------------------- GND

Note: The MPU9250 is an I2C sensor and uses the Arduino Wire library. Because the sensor is not 5V tolerant, we are using a 3.3 V 8 MHz Pro Mini or a 3.3 V Teensy 3.1. We have disabled the internal pull-ups used by the Wire library in the Wire.h/twi.c utility file. We are also using the 400 kHz fast I2C mode by setting the TWI_FREQ to 400000L /twi.h utility file. */

include "Wire.h"

//#include

// See also MPU-9250 Register Map and Descriptions, Revision 4.0, RM-MPU-9250A-00, Rev. 1.4, 9/9/2013 for registers not listed in // above document; the MPU9250 and MPU9150 are virtually identical but the latter has a different register map // //Magnetometer Registers

define AK8963_ADDRESS 0x0C

define AK8963_WHO_AM_I 0x00 // should return 0x48

define AK8963_INFO 0x01

define AK8963_ST1 0x02 // data ready status bit 0

define AK8963_XOUT_L 0x03 // data

define AK8963_XOUT_H 0x04

define AK8963_YOUT_L 0x05

define AK8963_YOUT_H 0x06

define AK8963_ZOUT_L 0x07

define AK8963_ZOUT_H 0x08

define AK8963_ST2 0x09 // Data overflow bit 3 and data read error status bit 2

define AK8963_CNTL 0x0A // Power down (0000), single-measurement (0001), self-test (1000) and Fuse ROM (1111) modes on bits 3:0

define AK8963_ASTC 0x0C // Self test control

define AK8963_I2CDIS 0x0F // I2C disable

define AK8963_ASAX 0x10 // Fuse ROM x-axis sensitivity adjustment value

define AK8963_ASAY 0x11 // Fuse ROM y-axis sensitivity adjustment value

define AK8963_ASAZ 0x12 // Fuse ROM z-axis sensitivity adjustment value

define SELF_TEST_X_GYRO 0x00

define SELF_TEST_Y_GYRO 0x01

define SELF_TEST_Z_GYRO 0x02

/*#define X_FINE_GAIN 0x03 // [7:0] fine gain

define Y_FINE_GAIN 0x04

define Z_FINE_GAIN 0x05

define XA_OFFSET_H 0x06 // User-defined trim values for accelerometer

define XA_OFFSET_L_TC 0x07

define YA_OFFSET_H 0x08

define YA_OFFSET_L_TC 0x09

define ZA_OFFSET_H 0x0A

define ZA_OFFSET_L_TC 0x0B */

define SELF_TEST_X_ACCEL 0x0D

define SELF_TEST_Y_ACCEL 0x0E

define SELF_TEST_Z_ACCEL 0x0F

define SELF_TEST_A 0x10

define XG_OFFSET_H 0x13 // User-defined trim values for gyroscope

define XG_OFFSET_L 0x14

define YG_OFFSET_H 0x15

define YG_OFFSET_L 0x16

define ZG_OFFSET_H 0x17

define ZG_OFFSET_L 0x18

define SMPLRT_DIV 0x19

define CONFIG 0x1A

define GYRO_CONFIG 0x1B

define ACCEL_CONFIG 0x1C

define ACCEL_CONFIG2 0x1D

define LP_ACCEL_ODR 0x1E

define WOM_THR 0x1F

define MOT_DUR 0x20 // Duration counter threshold for motion interrupt generation, 1 kHz rate, LSB = 1 ms

define ZMOT_THR 0x21 // Zero-motion detection threshold bits [7:0]

define ZRMOT_DUR 0x22 // Duration counter threshold for zero motion interrupt generation, 16 Hz rate, LSB = 64 ms

define FIFO_EN 0x23

define I2C_MST_CTRL 0x24

define I2C_SLV0_ADDR 0x25

define I2C_SLV0_REG 0x26

define I2C_SLV0_CTRL 0x27

define I2C_SLV1_ADDR 0x28

define I2C_SLV1_REG 0x29

define I2C_SLV1_CTRL 0x2A

define I2C_SLV2_ADDR 0x2B

define I2C_SLV2_REG 0x2C

define I2C_SLV2_CTRL 0x2D

define I2C_SLV3_ADDR 0x2E

define I2C_SLV3_REG 0x2F

define I2C_SLV3_CTRL 0x30

define I2C_SLV4_ADDR 0x31

define I2C_SLV4_REG 0x32

define I2C_SLV4_DO 0x33

define I2C_SLV4_CTRL 0x34

define I2C_SLV4_DI 0x35

define I2C_MST_STATUS 0x36

define INT_PIN_CFG 0x37

define INT_ENABLE 0x38

define DMP_INT_STATUS 0x39 // Check DMP interrupt

define INT_STATUS 0x3A

define ACCEL_XOUT_H 0x3B

define ACCEL_XOUT_L 0x3C

define ACCEL_YOUT_H 0x3D

define ACCEL_YOUT_L 0x3E

define ACCEL_ZOUT_H 0x3F

define ACCEL_ZOUT_L 0x40

define TEMP_OUT_H 0x41

define TEMP_OUT_L 0x42

define GYRO_XOUT_H 0x43

define GYRO_XOUT_L 0x44

define GYRO_YOUT_H 0x45

define GYRO_YOUT_L 0x46

define GYRO_ZOUT_H 0x47

define GYRO_ZOUT_L 0x48

define EXT_SENS_DATA_00 0x49

define EXT_SENS_DATA_01 0x4A

define EXT_SENS_DATA_02 0x4B

define EXT_SENS_DATA_03 0x4C

define EXT_SENS_DATA_04 0x4D

define EXT_SENS_DATA_05 0x4E

define EXT_SENS_DATA_06 0x4F

define EXT_SENS_DATA_07 0x50

define EXT_SENS_DATA_08 0x51

define EXT_SENS_DATA_09 0x52

define EXT_SENS_DATA_10 0x53

define EXT_SENS_DATA_11 0x54

define EXT_SENS_DATA_12 0x55

define EXT_SENS_DATA_13 0x56

define EXT_SENS_DATA_14 0x57

define EXT_SENS_DATA_15 0x58

define EXT_SENS_DATA_16 0x59

define EXT_SENS_DATA_17 0x5A

define EXT_SENS_DATA_18 0x5B

define EXT_SENS_DATA_19 0x5C

define EXT_SENS_DATA_20 0x5D

define EXT_SENS_DATA_21 0x5E

define EXT_SENS_DATA_22 0x5F

define EXT_SENS_DATA_23 0x60

define MOT_DETECT_STATUS 0x61

define I2C_SLV0_DO 0x63

define I2C_SLV1_DO 0x64

define I2C_SLV2_DO 0x65

define I2C_SLV3_DO 0x66

define I2C_MST_DELAY_CTRL 0x67

define SIGNAL_PATH_RESET 0x68

define MOT_DETECT_CTRL 0x69

define USER_CTRL 0x6A // Bit 7 enable DMP, bit 3 reset DMP

define PWR_MGMT_1 0x6B // Device defaults to the SLEEP mode

define PWR_MGMT_2 0x6C

define DMP_BANK 0x6D // Activates a specific bank in the DMP

define DMP_RW_PNT 0x6E // Set read/write pointer to a specific start address in specified DMP bank

define DMP_REG 0x6F // Register in DMP from which to read or to which to write

define DMP_REG_1 0x70

define DMP_REG_2 0x71

define FIFO_COUNTH 0x72

define FIFO_COUNTL 0x73

define FIFO_R_W 0x74

define WHO_AM_I_MPU9250 0x75 // Should return 0x71

define XA_OFFSET_H 0x77

define XA_OFFSET_L 0x78

define YA_OFFSET_H 0x7A

define YA_OFFSET_L 0x7B

define ZA_OFFSET_H 0x7D

define ZA_OFFSET_L 0x7E

// Using the MSENSR-9250 breakout board, ADO is set to 0 // Seven-bit device address is 110100 for ADO = 0 and 110101 for ADO = 1 //#define ADO 0

define MPU9250_ADDRESS 0x68 // Device address when ADO = 0

define AHRS true // set to false for basic data read

define SerialDebug true // set to true to get Serial output for debugging

// Set initial input parameters enum Ascale { AFS_2G = 0, AFS_4G, AFS_8G, AFS_16G };

enum Gscale { GFS_250DPS = 0, GFS_500DPS, GFS_1000DPS, GFS_2000DPS };

enum Mscale { MFS_14BITS = 0, // 0.6 mG per LSB MFS_16BITS // 0.15 mG per LSB };

// Specify sensor full scale uint8_t Gscale = GFS_250DPS; uint8_t Ascale = AFS_2G; uint8_t Mscale = MFS_16BITS; // Choose either 14-bit or 16-bit magnetometer resolution uint8_t Mmode = 0x02; // 2 for 8 Hz, 6 for 100 Hz continuous magnetometer data read float aRes, gRes, mRes; // scale resolutions per LSB for the sensors

// Pin definitions int intPin = 1; // These can be changed, 2 and 3 are the Arduinos ext int pins int myLed = 13;

int16_t accelCount[3]; // Stores the 16-bit signed accelerometer sensor output int16_t gyroCount[3]; // Stores the 16-bit signed gyro sensor output int16_t magCount[3]; // Stores the 16-bit signed magnetometer sensor output float magCalibration[3] = {0, 0, 0}, magbias[3] = {0, 0, 0}; // Factory mag calibration and mag bias float gyroBias[3] = {0, 0, 0}, accelBias[3] = {0, 0, 0}; // Bias corrections for gyro and accelerometer int16_t tempCount; // temperature raw count output float temperature; // Stores the real internal chip temperature in degrees Celsius float SelfTest[6]; // holds results of gyro and accelerometer self test

// global constants for 9 DoF fusion and AHRS (Attitude and Heading Reference System) float GyroMeasError = PI (40.0f / 180.0f); // gyroscope measurement error in rads/s (start at 40 deg/s) float GyroMeasDrift = PI (0.0f / 180.0f); // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s) // There is a tradeoff in the beta parameter between accuracy and response speed. // In the original Madgwick study, beta of 0.041 (corresponding to GyroMeasError of 2.7 degrees/s) was found to give optimal accuracy. // However, with this value, the LSM9SD0 response time is about 10 seconds to a stable initial quaternion. // Subsequent changes also require a longish lag time to a stable output, not fast enough for a quadcopter or robot car! // By increasing beta (GyroMeasError) by about a factor of fifteen, the response time constant is reduced to ~2 sec // I haven't noticed any reduction in solution accuracy. This is essentially the I coefficient in a PID control sense; // the bigger the feedback coefficient, the faster the solution converges, usually at the expense of accuracy. // In any case, this is the free parameter in the Madgwick filtering and fusion scheme. float beta = sqrt(3.0f / 4.0f) GyroMeasError; // compute beta float zeta = sqrt(3.0f / 4.0f) GyroMeasDrift; // compute zeta, the other free parameter in the Madgwick scheme usually set to a small or zero value

define Kp 2.0f * 5.0f // these are the free parameters in the Mahony filter and fusion scheme, Kp for proportional feedback, Ki for integral

define Ki 0.0f

uint32_t delt_t = 0; // used to control display output rate uint32_t count = 0, sumCount = 0; // used to control display output rate float pitch, yaw, roll; float deltat = 0.0f, sum = 0.0f; // integration interval for both filter schemes uint32_t lastUpdate = 0, firstUpdate = 0; // used to calculate integration interval uint32_t Now = 0; // used to calculate integration interval

float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values float q[4] = {1.0f, 0.0f, 0.0f, 0.0f}; // vector to hold quaternion float eInt[3] = {0.0f, 0.0f, 0.0f}; // vector to hold integral error for Mahony method

uint8_t newData = 0;

void setup() { Wire.begin(); // TWBR = 12; // 400 kbit/sec I2C speed // Setup for Master mode, pins 18/19, external pullups, 400kHz Wire.setClock(400000); Serial.begin(115200); delay(2000);

// Set up the interrupt pin, its set as active high, push-pull

pinMode(myLed, OUTPUT); digitalWrite(myLed, HIGH); delay(1000);

// Read the WHO_AM_I register, this is a good test of communication byte c = readByte(MPU9250_ADDRESS, WHO_AM_I_MPU9250); // Read WHO_AM_I register for MPU-9250 Serial.print("MPU9250 "); Serial.print("I AM "); Serial.print(c, HEX); Serial.print(" I should be "); Serial.println(0x71, HEX); delay(5000);

if (c == 0x71) // WHO_AM_I should always be 0x68 { Serial.println("MPU9250 is online...");

MPU9250SelfTest(SelfTest); // Start by performing self test and reporting values
Serial.print("x-axis self test: acceleration trim within : "); Serial.print(SelfTest[0],1); Serial.println("% of factory value");
Serial.print("y-axis self test: acceleration trim within : "); Serial.print(SelfTest[1],1); Serial.println("% of factory value");
Serial.print("z-axis self test: acceleration trim within : "); Serial.print(SelfTest[2],1); Serial.println("% of factory value");
Serial.print("x-axis self test: gyration trim within : "); Serial.print(SelfTest[3],1); Serial.println("% of factory value");
Serial.print("y-axis self test: gyration trim within : "); Serial.print(SelfTest[4],1); Serial.println("% of factory value");
Serial.print("z-axis self test: gyration trim within : "); Serial.print(SelfTest[5],1); Serial.println("% of factory value");
delay(5000);

calibrateMPU9250(gyroBias, accelBias); // Calibrate gyro and accelerometers, load biases in bias registers

delay(1000);

initMPU9250(); Serial.println("MPU9250 initialized for active data mode...."); // Initialize device for active mode read of acclerometer, gyroscope, and temperature

// Read the WHO_AM_I register of the magnetometer, this is a good test of communication byte d = readByte(AK8963_ADDRESS, AK8963_WHO_AM_I); // Read WHO_AM_I register for AK8963 Serial.print("AK8963 "); Serial.print("I AM "); Serial.print(d, HEX); Serial.print(" I should be "); Serial.println(0x48, HEX);

delay(1000);

// Get magnetometer calibration from AK8963 ROM initAK8963(magCalibration); Serial.println("AK8963 initialized for active data mode...."); // Initialize device for active mode read of magnetometer

if(SerialDebug) { // Serial.println("Calibration values: "); Serial.print("X-Axis sensitivity adjustment value "); Serial.println(magCalibration[0], 2); Serial.print("Y-Axis sensitivity adjustment value "); Serial.println(magCalibration[1], 2); Serial.print("Z-Axis sensitivity adjustment value "); Serial.println(magCalibration[2], 2); }

delay(1000); } else { Serial.print("Could not connect to MPU9250: 0x"); Serial.println(c, HEX); while(1) ; // Loop forever if communication doesn't happen }

// attaching the interrupt to microcontroller pin pinMode(intPin,INPUT); attachInterrupt(intPin,drdy_isr,RISING);

}

void drdy_isr(){ newData = 1; }

void loop() { // If intPin goes high, all data registers have new data //if (readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01) { // On interrupt, check if data ready interrupt if(newData == 1) { newData == 0; readAccelData(accelCount); // Read the x/y/z adc values getAres();

// 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];

readGyroData(gyroCount);  // Read the x/y/z adc values
getGres();

// Calculate the gyro value into actual degrees per second
gx = (float)gyroCount[0]*gRes;  // get actual gyro value, this depends on scale being set
gy = (float)gyroCount[1]*gRes;
gz = (float)gyroCount[2]*gRes;

//newMagData = (readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01);
//if(newMagData == true) { // wait for magnetometer data ready bit to be set
readMagData(magCount);  // Read the x/y/z adc values
getMres();
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

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

sum += deltat; // sum for averaging filter update rate sumCount++;

// Sensors x (y)-axis of the accelerometer is aligned with the y (x)-axis of the magnetometer; // the magnetometer z-axis (+ down) is opposite to z-axis (+ up) of accelerometer and gyro! // We have to make some allowance for this orientationmismatch in feeding the output to the quaternion filter. // For the MPU-9250, we have chosen a magnetic rotation that keeps the sensor forward along the x-axis just like // in the LSM9DS0 sensor. This rotation can be modified to allow any convenient orientation convention. // This is ok by aircraft orientation standards! // Pass gyro rate as rad/s MadgwickQuaternionUpdate(ax, ay, az, gxPI/180.0f, gyPI/180.0f, gzPI/180.0f, my, mx, mz); // MahonyQuaternionUpdate(ax, ay, az, gxPI/180.0f, gyPI/180.0f, gzPI/180.0f, my, mx, mz);

if (!AHRS) {
delt_t = millis() - count;
if(delt_t > 500) {

if(SerialDebug) {
// Print acceleration values in milligs!
Serial.print("X-acceleration: "); Serial.print(1000*ax); Serial.print(" mg ");
Serial.print("Y-acceleration: "); Serial.print(1000*ay); Serial.print(" mg ");
Serial.print("Z-acceleration: "); Serial.print(1000*az); Serial.println(" mg ");

// Print gyro values in degree/sec
Serial.print("X-gyro rate: "); Serial.print(gx, 3); Serial.print(" degrees/sec ");
Serial.print("Y-gyro rate: "); Serial.print(gy, 3); Serial.print(" degrees/sec ");
Serial.print("Z-gyro rate: "); Serial.print(gz, 3); Serial.println(" degrees/sec");

// Print mag values in degree/sec
Serial.print("X-mag field: "); Serial.print(mx); Serial.print(" mG ");
Serial.print("Y-mag field: "); Serial.print(my); Serial.print(" mG ");
Serial.print("Z-mag field: "); Serial.print(mz); Serial.println(" mG");

tempCount = readTempData();  // Read the adc values
temperature = ((float) tempCount) / 333.87 + 21.0; // Temperature in degrees Centigrade

// Print temperature in degrees Centigrade Serial.print("Temperature is "); Serial.print(temperature, 1); Serial.println(" degrees C"); // Print T values to tenths of s degree C }

count = millis();
}
}
else {

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

if(SerialDebug) {
Serial.print("ax = "); Serial.print((int)1000*ax);
Serial.print(" ay = "); Serial.print((int)1000*ay);
Serial.print(" az = "); Serial.print((int)1000*az); Serial.println(" mg");
Serial.print("gx = "); Serial.print( gx, 2);
Serial.print(" gy = "); Serial.print( gy, 2);
Serial.print(" gz = "); Serial.print( gz, 2); Serial.println(" deg/s");
Serial.print("mx = "); Serial.print( (int)mx );
Serial.print(" my = "); Serial.print( (int)my );
Serial.print(" mz = "); Serial.print( (int)mz ); Serial.println(" mG");

Serial.print("q0 = "); Serial.print(q[0]);
Serial.print(" qx = "); Serial.print(q[1]);
Serial.print(" qy = "); Serial.print(q[2]);
Serial.print(" qz = "); Serial.println(q[3]);
}

// 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 -= 13.8; // Declination at Danville, California is 13 degrees 48 minutes and 47 seconds on 2014-04-04 roll = 180.0f / PI;

if(SerialDebug) {
Serial.print("Yaw, Pitch, Roll: ");
Serial.print(yaw, 2);
Serial.print(", ");
Serial.print(pitch, 2);
Serial.print(", ");
Serial.println(roll, 2);

Serial.print("rate = "); Serial.print((float)sumCount/sum, 2); Serial.println(" Hz");
}

// With these settings the filter is updating at a ~145 Hz rate using the Madgwick scheme and
// >200 Hz using the Mahony scheme even though the display refreshes at only 2 Hz.
// The filter update rate is determined mostly by the mathematical steps in the respective algorithms,
// the processor speed (8 MHz for the 3.3V Pro Mini), and the magnetometer ODR:
// an ODR of 10 Hz for the magnetometer produce the above rates, maximum magnetometer ODR of 100 Hz produces
// filter update rates of 36 - 145 and ~38 Hz for the Madgwick and Mahony schemes, respectively.
// This is presumably because the magnetometer read takes longer than the gyro or accelerometer reads.
// This filter update rate should be fast enough to maintain accurate platform orientation for
// stabilization control of a fast-moving robot or quadcopter. Compare to the update rate of 200 Hz
// produced by the on-board Digital Motion Processor of Invensense's MPU6050 6 DoF and MPU9150 9DoF sensors.
// The 3.3 V 8 MHz Pro Mini is doing pretty well!
//display.setCursor(0, 40); display.print("rt: "); display.print((float) sumCount / sum, 2); display.print(" Hz");
//display.display();

digitalWrite(myLed, !digitalRead(myLed));
count = millis();
sumCount = 0;
sum = 0;
}
}

}

//=================================================================================================================== //====== Set of useful function to access acceleration. gyroscope, magnetometer, and temperature data //===================================================================================================================

void getMres() { switch (Mscale) { // Possible magnetometer scales (and their register bit settings) are: // 14 bit resolution (0) and 16 bit resolution (1) case MFS_14BITS: mRes = 10.4912./8190.; // Proper scale to return milliGauss break; case MFS_16BITS: mRes = 10.4912./32760.0; // Proper scale to return milliGauss break; } }

void getGres() { switch (Gscale) { // Possible gyro scales (and their register bit settings) are: // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS (11). // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value: case GFS_250DPS: gRes = 250.0/32768.0; break; case GFS_500DPS: gRes = 500.0/32768.0; break; case GFS_1000DPS: gRes = 1000.0/32768.0; break; case GFS_2000DPS: gRes = 2000.0/32768.0; break; } }

void getAres() { switch (Ascale) { // Possible accelerometer scales (and their register bit settings) are: // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs (11). // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value: case AFS_2G: aRes = 2.0/32768.0; break; case AFS_4G: aRes = 4.0/32768.0; break; case AFS_8G: aRes = 8.0/32768.0; break; case AFS_16G: aRes = 16.0/32768.0; break; } }

void readAccelData(int16_t * destination) { uint8_t rawData[6]; // x/y/z accel register data stored here readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array destination[0] = ((int16_t)rawData[0] << 8) | rawData[1] ; // Turn the MSB and LSB into a signed 16-bit value destination[1] = ((int16_t)rawData[2] << 8) | rawData[3] ; destination[2] = ((int16_t)rawData[4] << 8) | rawData[5] ; }

void readGyroData(int16_t * destination) { uint8_t rawData[6]; // x/y/z gyro register data stored here readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array destination[0] = ((int16_t)rawData[0] << 8) | rawData[1] ; // Turn the MSB and LSB into a signed 16-bit value destination[1] = ((int16_t)rawData[2] << 8) | rawData[3] ; destination[2] = ((int16_t)rawData[4] << 8) | rawData[5] ; }

void readMagData(int16_t * destination) { uint8_t rawData[7]; // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]); // Read the six raw data and ST2 registers sequentially into data array uint8_t c = rawData[6]; // End data read by reading ST2 register if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data destination[0] = ((int16_t)rawData[1] << 8) | rawData[0] ; // Turn the MSB and LSB into a signed 16-bit value destination[1] = ((int16_t)rawData[3] << 8) | rawData[2] ; // Data stored as little Endian destination[2] = ((int16_t)rawData[5] << 8) | rawData[4] ; } } }

int16_t readTempData() { uint8_t rawData[2]; // x/y/z gyro register data stored here readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]); // Read the two raw data registers sequentially into data array return ((int16_t)rawData[0] << 8) | rawData[1] ; // Turn the MSB and LSB into a 16-bit value }

void initAK8963(float * destination) { // First extract the factory calibration for each magnetometer axis uint8_t rawData[3]; // x/y/z gyro calibration data stored here writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer delay(10); writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode delay(10); readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]); // Read the x-, y-, and z-axis calibration values destination[0] = (float)(rawData[0] - 128)/256. + 1.; // Return x-axis sensitivity adjustment values, etc. destination[1] = (float)(rawData[1] - 128)/256. + 1.; destination[2] = (float)(rawData[2] - 128)/256. + 1.; writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer delay(10); // Configure the magnetometer for continuous read and highest resolution // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register, // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR delay(10); }

void initMPU9250() { // wake up device writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors delay(100); // Wait for all registers to reset

// get stable time source writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01); // Auto select clock source to be PLL gyroscope reference if ready else delay(200);

// Configure Gyro and Thermometer // Disable FSYNC and set thermometer and gyro bandwidth to 41 and 42 Hz, respectively; // minimum delay time for this setting is 5.9 ms, which means sensor fusion update rates cannot // be higher than 1 / 0.0059 = 170 Hz // DLPF_CFG = bits 2:0 = 011; this limits the sample rate to 1000 Hz for both // With the MPU9250, it is possible to get gyro sample rates of 32 kHz (!), 8 kHz, or 1 kHz writeByte(MPU9250_ADDRESS, CONFIG, 0x03);

// Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV) writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04); // Use a 200 Hz rate; a rate consistent with the filter update rate // determined inset in CONFIG above

// Set gyroscope full scale range // Range selects FS_SEL and GFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3 uint8_t c = readByte(MPU9250_ADDRESS, GYRO_CONFIG); // get current GYRO_CONFIG register value // c = c & ~0xE0; // Clear self-test bits [7:5] c = c & ~0x03; // Clear Fchoice bits [1:0] c = c & ~0x18; // Clear GFS bits [4:3] c = c | Gscale << 3; // Set full scale range for the gyro // c =| 0x00; // Set Fchoice for the gyro to 11 by writing its inverse to bits 1:0 of GYRO_CONFIG writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c ); // Write new GYRO_CONFIG value to register

// Set accelerometer full-scale range configuration c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG); // get current ACCEL_CONFIG register value // c = c & ~0xE0; // Clear self-test bits [7:5] c = c & ~0x18; // Clear AFS bits [4:3] c = c | Ascale << 3; // Set full scale range for the accelerometer writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c); // Write new ACCEL_CONFIG register value

// Set accelerometer sample rate configuration // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2); // get current ACCEL_CONFIG2 register value c = c & ~0x0F; // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0]) c = c | 0x03; // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c); // Write new ACCEL_CONFIG2 register value

// The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting

// Configure Interrupts and Bypass Enable // Set interrupt pin active high, push-pull, hold interrupt pin level HIGH until interrupt cleared, // clear on read of INT_STATUS, and enable I2C_BYPASS_EN so additional chips // can join the I2C bus and all can be controlled by the Arduino as master //writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22); writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x12); writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01); // Enable data ready (bit 0) interrupt delay(100); }

// Function which accumulates gyro and accelerometer data after device initialization. It calculates the average // of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers. void calibrateMPU9250(float dest1, float dest2) { uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data uint16_t ii, packet_count, fifo_count; int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};

// reset device writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device delay(100);

// get stable time source; Auto select clock source to be PLL gyroscope reference if ready // else use the internal oscillator, bits 2:0 = 001 writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01); writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00); delay(200);

// Configure device for bias calculation writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00); // Disable all interrupts writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00); // Disable FIFO writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Turn on internal clock source writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00); // Disable FIFO and I2C master modes writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C); // Reset FIFO and DMP delay(15);

// Configure MPU6050 gyro and accelerometer for bias calculation writeByte(MPU9250_ADDRESS, CONFIG, 0x01); // Set low-pass filter to 188 Hz writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set sample rate to 1 kHz writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00); // Set gyro full-scale to 250 degrees per second, maximum sensitivity writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity

uint16_t gyrosensitivity = 131; // = 131 LSB/degrees/sec uint16_t accelsensitivity = 16384; // = 16384 LSB/g

// Configure FIFO to capture accelerometer and gyro data for bias calculation

writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40); // Enable FIFO writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78); // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9150) delay(40); // accumulate 40 samples in 40 milliseconds = 480 bytes

// At end of sample accumulation, turn off FIFO sensor read writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00); // Disable gyro and accelerometer sensors for FIFO readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count fifo_count = ((uint16_t)data[0] << 8) | data[1]; packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging

for (ii = 0; ii < packet_count; ii++) { int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0}; readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1] ) ; // Form signed 16-bit integer for each sample in FIFO accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3] ) ; accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5] ) ; gyro_temp[0] = (int16_t) (((int16_t)data[6] << 8) | data[7] ) ; gyro_temp[1] = (int16_t) (((int16_t)data[8] << 8) | data[9] ) ; gyro_temp[2] = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;

accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
accel_bias[1] += (int32_t) accel_temp[1];
accel_bias[2] += (int32_t) accel_temp[2];
gyro_bias[0]  += (int32_t) gyro_temp[0];
gyro_bias[1]  += (int32_t) gyro_temp[1];
gyro_bias[2]  += (int32_t) gyro_temp[2];

} accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases accel_bias[1] /= (int32_t) packet_count; accel_bias[2] /= (int32_t) packet_count; gyro_bias[0] /= (int32_t) packet_count; gyro_bias[1] /= (int32_t) packet_count; gyro_bias[2] /= (int32_t) packet_count;

if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;} // Remove gravity from the z-axis accelerometer bias calculation else {accel_bias[2] += (int32_t) accelsensitivity;}

// Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup data[0] = (-gyro_bias[0]/4 >> 8) & 0xFF; // Divide by 4 to get 32.9 LSB per deg/s to conform to expected bias input format data[1] = (-gyro_bias[0]/4) & 0xFF; // Biases are additive, so change sign on calculated average gyro biases data[2] = (-gyro_bias[1]/4 >> 8) & 0xFF; data[3] = (-gyro_bias[1]/4) & 0xFF; data[4] = (-gyro_bias[2]/4 >> 8) & 0xFF; data[5] = (-gyro_bias[2]/4) & 0xFF;

// Push gyro biases to hardware registers writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]); writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]); writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]); writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]); writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]); writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);

// Output scaled gyro biases for display in the main program dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity; dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;

// Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain // factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold // non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature // compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that // the accelerometer biases calculated above must be divided by 8.

int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values accel_bias_reg[0] = (int32_t) (((int16_t)data[0] << 8) | data[1]); readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]); accel_bias_reg[1] = (int32_t) (((int16_t)data[0] << 8) | data[1]); readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]); accel_bias_reg[2] = (int32_t) (((int16_t)data[0] << 8) | data[1]);

uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis

for(ii = 0; ii < 3; ii++) { if((accel_bias_reg[ii] & mask)) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit }

// Construct total accelerometer bias, including calculated average accelerometer bias from above accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale) accel_bias_reg[1] -= (accel_bias[1]/8); accel_bias_reg[2] -= (accel_bias[2]/8);

data[0] = (accel_bias_reg[0] >> 8) & 0xFF; data[1] = (accel_bias_reg[0]) & 0xFF; data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers data[2] = (accel_bias_reg[1] >> 8) & 0xFF; data[3] = (accel_bias_reg[1]) & 0xFF; data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers data[4] = (accel_bias_reg[2] >> 8) & 0xFF; data[5] = (accel_bias_reg[2]) & 0xFF; data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers

// Apparently this is not working for the acceleration biases in the MPU-9250 // Are we handling the temperature correction bit properly? // Push accelerometer biases to hardware registers writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]); writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]); writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]); writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]); writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]); writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);

// Output scaled accelerometer biases for display in the main program dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; dest2[1] = (float)accel_bias[1]/(float)accelsensitivity; dest2[2] = (float)accel_bias[2]/(float)accelsensitivity; }

// Accelerometer and gyroscope self test; check calibration wrt factory settings void MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass { uint8_t rawData[6] = {0, 0, 0, 0, 0, 0}; uint8_t selfTest[6]; int32_t gAvg[3] = {0}, aAvg[3] = {0}, aSTAvg[3] = {0}, gSTAvg[3] = {0}; float factoryTrim[6]; uint8_t FS = 0;

writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz writeByte(MPU9250_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz writeByte(MPU9250_ADDRESS, GYRO_CONFIG, FS<<3); // Set full scale range for the gyro to 250 dps writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, FS<<3); // Set full scale range for the accelerometer to 2 g

for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer

readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;

readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);       // Read the six raw data registers sequentially into data array

gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; }

for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average current readings aAvg[ii] /= 200; gAvg[ii] /= 200; }

// Configure the accelerometer for self-test writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s delay(25); // Delay a while to let the device stabilize

for( int ii = 0; ii < 200; ii++) { // get average self-test values of gyro and acclerometer

readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;

readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array

gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; }

for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average self-test readings aSTAvg[ii] /= 200; gSTAvg[ii] /= 200; }

// Configure the gyro and accelerometer for normal operation writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00); delay(25); // Delay a while to let the device stabilize

// Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results

// Retrieve factory self-test value from self-test code reads factoryTrim[0] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation factoryTrim[1] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation factoryTrim[2] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation factoryTrim[3] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation factoryTrim[4] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation factoryTrim[5] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation

// Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response // To get percent, must multiply by 100 for (int i = 0; i < 3; i++) { destination[i] = 100.0((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i] - 100.; // Report percent differences destination[i+3] = 100.0((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3] - 100.; // Report percent differences }

}

// I2C read/write functions for the MPU9250 and AK8963 sensors

    void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)

{ Wire.beginTransmission(address); // Initialize the Tx buffer Wire.write(subAddress); // Put slave register address in Tx buffer Wire.write(data); // Put data in Tx buffer Wire.endTransmission(); // Send the Tx buffer }

    uint8_t readByte(uint8_t address, uint8_t subAddress)

{ uint8_t data; // data will store the register data Wire.beginTransmission(address); // Initialize the Tx buffer Wire.write(subAddress); // Put slave register address in Tx buffer Wire.endTransmission(); // Send the Tx buffer, but send a restart to keep connection alive // Wire.endTransmission(false); // Send the Tx buffer, but send a restart to keep connection alive // Wire.requestFrom(address, 1); // Read one byte from slave register address Wire.requestFrom(address, (size_t) 1); // Read one byte from slave register address data = Wire.read(); // Fill Rx buffer with result return data; // Return data read from slave register }

    void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)

{ Wire.beginTransmission(address); // Initialize the Tx buffer Wire.write(subAddress); // Put slave register address in Tx buffer Wire.endTransmission(); // Send the Tx buffer, but send a restart to keep connection alive // Wire.endTransmission(false); // Send the Tx buffer, but send a restart to keep connection alive uint8_t i = 0; // Wire.requestFrom(address, count); // Read bytes from slave register address Wire.requestFrom(address, (size_t) count); // Read bytes from slave register address while (Wire.available()) { dest[i++] = Wire.read(); } // Put read results in the Rx buffer }

— You are receiving this because you commented. Reply to this email directly, view it on GitHub https://github.com/kriswiner/MPU9250/issues/325#issuecomment-438377963, or mute the thread https://github.com/notifications/unsubscribe-auth/AGY1qpJboM5kWbgxQobpxU47Rj5ZIh_Mks5uuwtOgaJpZM4YcLWY .

[kriswiner]

By the way, I finally got around to writing a sketch for two MPU9250s on the same bus. I get 2 kHz fusion rate for both when running at 400 kHz I2C bus speed, 10 iterations of the filter using an STM32L4. If I up the I2C speed to 1 MHz the rate doubles, of course.

On Tue, Nov 13, 2018 at 10:34 AM Tlera Corporation tleracorp@gmail.com wrote:

There are a lot of problems with this sketch. Not sure why you chose this one to play with.

First of all, the accel and gyro data should be read in one operation, the resolutions (gerAres(),eg) should be done in setup just once, the mag really ought to be run at 100 Hz, the mag biases are hard coded (obviously wrong for your sensor), the sensor data order into the Madgwick filter is wrong, etc. Not sure if these have anything to do with your timing results.

You might try changing PI to in-sketch defined pi = 3.14159f. This speeded up the fuson filter by 10x when I did this for the STM32L4.

In short, this is not a good vehicle for exploring timing issues. At a minimum I would limit the Madgwick fusion in a for loop to 10 iterations, correct some of the obvious sketch errors and try the timing test again.

On Tue, Nov 13, 2018 at 10:11 AM Mike S notifications@github.com wrote:

Thanks for getting back to me - here is the sketch that I am running. Basically your sketch with modification for newData unless I messed something up somewhere with the interrupt: Oh, think i forgot, the strange timing results are on the T3.5 running wire. Just wanted to be consisted when I did the comparisons.

/* 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.

SDA and SCL should have external pull-up resistors (to 3.3V). 10k resistors are on the EMSENSR-9250 breakout board.

Hardware setup: MPU9250 Breakout --------- Arduino VDD ---------------------- 3.3V VDDI --------------------- 3.3V SDA ----------------------- A4 SCL ----------------------- A5 GND ---------------------- GND

Note: The MPU9250 is an I2C sensor and uses the Arduino Wire library. Because the sensor is not 5V tolerant, we are using a 3.3 V 8 MHz Pro Mini or a 3.3 V Teensy 3.1. We have disabled the internal pull-ups used by the Wire library in the Wire.h/twi.c utility file. We are also using the 400 kHz fast I2C mode by setting the TWI_FREQ to 400000L /twi.h utility file. */

include "Wire.h"

//#include

// See also MPU-9250 Register Map and Descriptions, Revision 4.0, RM-MPU-9250A-00, Rev. 1.4, 9/9/2013 for registers not listed in // above document; the MPU9250 and MPU9150 are virtually identical but the latter has a different register map // //Magnetometer Registers

define AK8963_ADDRESS 0x0C

define AK8963_WHO_AM_I 0x00 // should return 0x48

define AK8963_INFO 0x01

define AK8963_ST1 0x02 // data ready status bit 0

define AK8963_XOUT_L 0x03 // data

define AK8963_XOUT_H 0x04

define AK8963_YOUT_L 0x05

define AK8963_YOUT_H 0x06

define AK8963_ZOUT_L 0x07

define AK8963_ZOUT_H 0x08

define AK8963_ST2 0x09 // Data overflow bit 3 and data read error status bit 2

define AK8963_CNTL 0x0A // Power down (0000), single-measurement (0001), self-test (1000) and Fuse ROM (1111) modes on bits 3:0

define AK8963_ASTC 0x0C // Self test control

define AK8963_I2CDIS 0x0F // I2C disable

define AK8963_ASAX 0x10 // Fuse ROM x-axis sensitivity adjustment value

define AK8963_ASAY 0x11 // Fuse ROM y-axis sensitivity adjustment value

define AK8963_ASAZ 0x12 // Fuse ROM z-axis sensitivity adjustment value

define SELF_TEST_X_GYRO 0x00

define SELF_TEST_Y_GYRO 0x01

define SELF_TEST_Z_GYRO 0x02

/*#define X_FINE_GAIN 0x03 // [7:0] fine gain

define Y_FINE_GAIN 0x04

define Z_FINE_GAIN 0x05

define XA_OFFSET_H 0x06 // User-defined trim values for accelerometer

define XA_OFFSET_L_TC 0x07

define YA_OFFSET_H 0x08

define YA_OFFSET_L_TC 0x09

define ZA_OFFSET_H 0x0A

define ZA_OFFSET_L_TC 0x0B */

define SELF_TEST_X_ACCEL 0x0D

define SELF_TEST_Y_ACCEL 0x0E

define SELF_TEST_Z_ACCEL 0x0F

define SELF_TEST_A 0x10

define XG_OFFSET_H 0x13 // User-defined trim values for gyroscope

define XG_OFFSET_L 0x14

define YG_OFFSET_H 0x15

define YG_OFFSET_L 0x16

define ZG_OFFSET_H 0x17

define ZG_OFFSET_L 0x18

define SMPLRT_DIV 0x19

define CONFIG 0x1A

define GYRO_CONFIG 0x1B

define ACCEL_CONFIG 0x1C

define ACCEL_CONFIG2 0x1D

define LP_ACCEL_ODR 0x1E

define WOM_THR 0x1F

define MOT_DUR 0x20 // Duration counter threshold for motion interrupt generation, 1 kHz rate, LSB = 1 ms

define ZMOT_THR 0x21 // Zero-motion detection threshold bits [7:0]

define ZRMOT_DUR 0x22 // Duration counter threshold for zero motion interrupt generation, 16 Hz rate, LSB = 64 ms

define FIFO_EN 0x23

define I2C_MST_CTRL 0x24

define I2C_SLV0_ADDR 0x25

define I2C_SLV0_REG 0x26

define I2C_SLV0_CTRL 0x27

define I2C_SLV1_ADDR 0x28

define I2C_SLV1_REG 0x29

define I2C_SLV1_CTRL 0x2A

define I2C_SLV2_ADDR 0x2B

define I2C_SLV2_REG 0x2C

define I2C_SLV2_CTRL 0x2D

define I2C_SLV3_ADDR 0x2E

define I2C_SLV3_REG 0x2F

define I2C_SLV3_CTRL 0x30

define I2C_SLV4_ADDR 0x31

define I2C_SLV4_REG 0x32

define I2C_SLV4_DO 0x33

define I2C_SLV4_CTRL 0x34

define I2C_SLV4_DI 0x35

define I2C_MST_STATUS 0x36

define INT_PIN_CFG 0x37

define INT_ENABLE 0x38

define DMP_INT_STATUS 0x39 // Check DMP interrupt

define INT_STATUS 0x3A

define ACCEL_XOUT_H 0x3B

define ACCEL_XOUT_L 0x3C

define ACCEL_YOUT_H 0x3D

define ACCEL_YOUT_L 0x3E

define ACCEL_ZOUT_H 0x3F

define ACCEL_ZOUT_L 0x40

define TEMP_OUT_H 0x41

define TEMP_OUT_L 0x42

define GYRO_XOUT_H 0x43

define GYRO_XOUT_L 0x44

define GYRO_YOUT_H 0x45

define GYRO_YOUT_L 0x46

define GYRO_ZOUT_H 0x47

define GYRO_ZOUT_L 0x48

define EXT_SENS_DATA_00 0x49

define EXT_SENS_DATA_01 0x4A

define EXT_SENS_DATA_02 0x4B

define EXT_SENS_DATA_03 0x4C

define EXT_SENS_DATA_04 0x4D

define EXT_SENS_DATA_05 0x4E

define EXT_SENS_DATA_06 0x4F

define EXT_SENS_DATA_07 0x50

define EXT_SENS_DATA_08 0x51

define EXT_SENS_DATA_09 0x52

define EXT_SENS_DATA_10 0x53

define EXT_SENS_DATA_11 0x54

define EXT_SENS_DATA_12 0x55

define EXT_SENS_DATA_13 0x56

define EXT_SENS_DATA_14 0x57

define EXT_SENS_DATA_15 0x58

define EXT_SENS_DATA_16 0x59

define EXT_SENS_DATA_17 0x5A

define EXT_SENS_DATA_18 0x5B

define EXT_SENS_DATA_19 0x5C

define EXT_SENS_DATA_20 0x5D

define EXT_SENS_DATA_21 0x5E

define EXT_SENS_DATA_22 0x5F

define EXT_SENS_DATA_23 0x60

define MOT_DETECT_STATUS 0x61

define I2C_SLV0_DO 0x63

define I2C_SLV1_DO 0x64

define I2C_SLV2_DO 0x65

define I2C_SLV3_DO 0x66

define I2C_MST_DELAY_CTRL 0x67

define SIGNAL_PATH_RESET 0x68

define MOT_DETECT_CTRL 0x69

define USER_CTRL 0x6A // Bit 7 enable DMP, bit 3 reset DMP

define PWR_MGMT_1 0x6B // Device defaults to the SLEEP mode

define PWR_MGMT_2 0x6C

define DMP_BANK 0x6D // Activates a specific bank in the DMP

define DMP_RW_PNT 0x6E // Set read/write pointer to a specific start address in specified DMP bank

define DMP_REG 0x6F // Register in DMP from which to read or to which to write

define DMP_REG_1 0x70

define DMP_REG_2 0x71

define FIFO_COUNTH 0x72

define FIFO_COUNTL 0x73

define FIFO_R_W 0x74

define WHO_AM_I_MPU9250 0x75 // Should return 0x71

define XA_OFFSET_H 0x77

define XA_OFFSET_L 0x78

define YA_OFFSET_H 0x7A

define YA_OFFSET_L 0x7B

define ZA_OFFSET_H 0x7D

define ZA_OFFSET_L 0x7E

// Using the MSENSR-9250 breakout board, ADO is set to 0 // Seven-bit device address is 110100 for ADO = 0 and 110101 for ADO = 1 //#define ADO 0

define MPU9250_ADDRESS 0x68 // Device address when ADO = 0

define AHRS true // set to false for basic data read

define SerialDebug true // set to true to get Serial output for debugging

// Set initial input parameters enum Ascale { AFS_2G = 0, AFS_4G, AFS_8G, AFS_16G };

enum Gscale { GFS_250DPS = 0, GFS_500DPS, GFS_1000DPS, GFS_2000DPS };

enum Mscale { MFS_14BITS = 0, // 0.6 mG per LSB MFS_16BITS // 0.15 mG per LSB };

// Specify sensor full scale uint8_t Gscale = GFS_250DPS; uint8_t Ascale = AFS_2G; uint8_t Mscale = MFS_16BITS; // Choose either 14-bit or 16-bit magnetometer resolution uint8_t Mmode = 0x02; // 2 for 8 Hz, 6 for 100 Hz continuous magnetometer data read float aRes, gRes, mRes; // scale resolutions per LSB for the sensors

// Pin definitions int intPin = 1; // These can be changed, 2 and 3 are the Arduinos ext int pins int myLed = 13;

int16_t accelCount[3]; // Stores the 16-bit signed accelerometer sensor output int16_t gyroCount[3]; // Stores the 16-bit signed gyro sensor output int16_t magCount[3]; // Stores the 16-bit signed magnetometer sensor output float magCalibration[3] = {0, 0, 0}, magbias[3] = {0, 0, 0}; // Factory mag calibration and mag bias float gyroBias[3] = {0, 0, 0}, accelBias[3] = {0, 0, 0}; // Bias corrections for gyro and accelerometer int16_t tempCount; // temperature raw count output float temperature; // Stores the real internal chip temperature in degrees Celsius float SelfTest[6]; // holds results of gyro and accelerometer self test

// global constants for 9 DoF fusion and AHRS (Attitude and Heading Reference System) float GyroMeasError = PI (40.0f / 180.0f); // gyroscope measurement error in rads/s (start at 40 deg/s) float GyroMeasDrift = PI (0.0f / 180.0f); // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s) // There is a tradeoff in the beta parameter between accuracy and response speed. // In the original Madgwick study, beta of 0.041 (corresponding to GyroMeasError of 2.7 degrees/s) was found to give optimal accuracy. // However, with this value, the LSM9SD0 response time is about 10 seconds to a stable initial quaternion. // Subsequent changes also require a longish lag time to a stable output, not fast enough for a quadcopter or robot car! // By increasing beta (GyroMeasError) by about a factor of fifteen, the response time constant is reduced to ~2 sec // I haven't noticed any reduction in solution accuracy. This is essentially the I coefficient in a PID control sense; // the bigger the feedback coefficient, the faster the solution converges, usually at the expense of accuracy. // In any case, this is the free parameter in the Madgwick filtering and fusion scheme. float beta = sqrt(3.0f / 4.0f) GyroMeasError; // compute beta float zeta = sqrt(3.0f / 4.0f) GyroMeasDrift; // compute zeta, the other free parameter in the Madgwick scheme usually set to a small or zero value

define Kp 2.0f * 5.0f // these are the free parameters in the Mahony filter and fusion scheme, Kp for proportional feedback, Ki for integral

define Ki 0.0f

uint32_t delt_t = 0; // used to control display output rate uint32_t count = 0, sumCount = 0; // used to control display output rate float pitch, yaw, roll; float deltat = 0.0f, sum = 0.0f; // integration interval for both filter schemes uint32_t lastUpdate = 0, firstUpdate = 0; // used to calculate integration interval uint32_t Now = 0; // used to calculate integration interval

float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values float q[4] = {1.0f, 0.0f, 0.0f, 0.0f}; // vector to hold quaternion float eInt[3] = {0.0f, 0.0f, 0.0f}; // vector to hold integral error for Mahony method

uint8_t newData = 0;

void setup() { Wire.begin(); // TWBR = 12; // 400 kbit/sec I2C speed // Setup for Master mode, pins 18/19, external pullups, 400kHz Wire.setClock(400000); Serial.begin(115200); delay(2000);

// Set up the interrupt pin, its set as active high, push-pull

pinMode(myLed, OUTPUT); digitalWrite(myLed, HIGH); delay(1000);

// Read the WHO_AM_I register, this is a good test of communication byte c = readByte(MPU9250_ADDRESS, WHO_AM_I_MPU9250); // Read WHO_AM_I register for MPU-9250 Serial.print("MPU9250 "); Serial.print("I AM "); Serial.print(c, HEX); Serial.print(" I should be "); Serial.println(0x71, HEX); delay(5000);

if (c == 0x71) // WHO_AM_I should always be 0x68 { Serial.println("MPU9250 is online...");

MPU9250SelfTest(SelfTest); // Start by performing self test and reporting values
Serial.print("x-axis self test: acceleration trim within : "); Serial.print(SelfTest[0],1); Serial.println("% of factory value");
Serial.print("y-axis self test: acceleration trim within : "); Serial.print(SelfTest[1],1); Serial.println("% of factory value");
Serial.print("z-axis self test: acceleration trim within : "); Serial.print(SelfTest[2],1); Serial.println("% of factory value");
Serial.print("x-axis self test: gyration trim within : "); Serial.print(SelfTest[3],1); Serial.println("% of factory value");
Serial.print("y-axis self test: gyration trim within : "); Serial.print(SelfTest[4],1); Serial.println("% of factory value");
Serial.print("z-axis self test: gyration trim within : "); Serial.print(SelfTest[5],1); Serial.println("% of factory value");
delay(5000);

calibrateMPU9250(gyroBias, accelBias); // Calibrate gyro and accelerometers, load biases in bias registers

delay(1000);

initMPU9250(); Serial.println("MPU9250 initialized for active data mode...."); // Initialize device for active mode read of acclerometer, gyroscope, and temperature

// Read the WHO_AM_I register of the magnetometer, this is a good test of communication byte d = readByte(AK8963_ADDRESS, AK8963_WHO_AM_I); // Read WHO_AM_I register for AK8963 Serial.print("AK8963 "); Serial.print("I AM "); Serial.print(d, HEX); Serial.print(" I should be "); Serial.println(0x48, HEX);

delay(1000);

// Get magnetometer calibration from AK8963 ROM initAK8963(magCalibration); Serial.println("AK8963 initialized for active data mode...."); // Initialize device for active mode read of magnetometer

if(SerialDebug) { // Serial.println("Calibration values: "); Serial.print("X-Axis sensitivity adjustment value "); Serial.println(magCalibration[0], 2); Serial.print("Y-Axis sensitivity adjustment value "); Serial.println(magCalibration[1], 2); Serial.print("Z-Axis sensitivity adjustment value "); Serial.println(magCalibration[2], 2); }

delay(1000); } else { Serial.print("Could not connect to MPU9250: 0x"); Serial.println(c, HEX); while(1) ; // Loop forever if communication doesn't happen }

// attaching the interrupt to microcontroller pin pinMode(intPin,INPUT); attachInterrupt(intPin,drdy_isr,RISING);

}

void drdy_isr(){ newData = 1; }

void loop() { // If intPin goes high, all data registers have new data //if (readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01) { // On interrupt, check if data ready interrupt if(newData == 1) { newData == 0; readAccelData(accelCount); // Read the x/y/z adc values getAres();

// 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];

readGyroData(gyroCount);  // Read the x/y/z adc values
getGres();

// Calculate the gyro value into actual degrees per second
gx = (float)gyroCount[0]*gRes;  // get actual gyro value, this depends on scale being set
gy = (float)gyroCount[1]*gRes;
gz = (float)gyroCount[2]*gRes;

//newMagData = (readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01);
//if(newMagData == true) { // wait for magnetometer data ready bit to be set
readMagData(magCount);  // Read the x/y/z adc values
getMres();
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

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

sum += deltat; // sum for averaging filter update rate sumCount++;

// Sensors x (y)-axis of the accelerometer is aligned with the y (x)-axis of the magnetometer; // the magnetometer z-axis (+ down) is opposite to z-axis (+ up) of accelerometer and gyro! // We have to make some allowance for this orientationmismatch in feeding the output to the quaternion filter. // For the MPU-9250, we have chosen a magnetic rotation that keeps the sensor forward along the x-axis just like // in the LSM9DS0 sensor. This rotation can be modified to allow any convenient orientation convention. // This is ok by aircraft orientation standards! // Pass gyro rate as rad/s MadgwickQuaternionUpdate(ax, ay, az, gxPI/180.0f, gyPI/180.0f, gzPI/180.0f, my, mx, mz); // MahonyQuaternionUpdate(ax, ay, az, gxPI/180.0f, gyPI/180.0f, gzPI/180.0f, my, mx, mz);

if (!AHRS) {
delt_t = millis() - count;
if(delt_t > 500) {

if(SerialDebug) {
// Print acceleration values in milligs!
Serial.print("X-acceleration: "); Serial.print(1000*ax); Serial.print(" mg ");
Serial.print("Y-acceleration: "); Serial.print(1000*ay); Serial.print(" mg ");
Serial.print("Z-acceleration: "); Serial.print(1000*az); Serial.println(" mg ");

// Print gyro values in degree/sec
Serial.print("X-gyro rate: "); Serial.print(gx, 3); Serial.print(" degrees/sec ");
Serial.print("Y-gyro rate: "); Serial.print(gy, 3); Serial.print(" degrees/sec ");
Serial.print("Z-gyro rate: "); Serial.print(gz, 3); Serial.println(" degrees/sec");

// Print mag values in degree/sec
Serial.print("X-mag field: "); Serial.print(mx); Serial.print(" mG ");
Serial.print("Y-mag field: "); Serial.print(my); Serial.print(" mG ");
Serial.print("Z-mag field: "); Serial.print(mz); Serial.println(" mG");

tempCount = readTempData();  // Read the adc values
temperature = ((float) tempCount) / 333.87 + 21.0; // Temperature in degrees Centigrade

// Print temperature in degrees Centigrade Serial.print("Temperature is "); Serial.print(temperature, 1); Serial.println(" degrees C"); // Print T values to tenths of s degree C }

count = millis();
}
}
else {

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

if(SerialDebug) {
Serial.print("ax = "); Serial.print((int)1000*ax);
Serial.print(" ay = "); Serial.print((int)1000*ay);
Serial.print(" az = "); Serial.print((int)1000*az); Serial.println(" mg");
Serial.print("gx = "); Serial.print( gx, 2);
Serial.print(" gy = "); Serial.print( gy, 2);
Serial.print(" gz = "); Serial.print( gz, 2); Serial.println(" deg/s");
Serial.print("mx = "); Serial.print( (int)mx );
Serial.print(" my = "); Serial.print( (int)my );
Serial.print(" mz = "); Serial.print( (int)mz ); Serial.println(" mG");

Serial.print("q0 = "); Serial.print(q[0]);
Serial.print(" qx = "); Serial.print(q[1]);
Serial.print(" qy = "); Serial.print(q[2]);
Serial.print(" qz = "); Serial.println(q[3]);
}

// 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 -= 13.8; // Declination at Danville, California is 13 degrees 48 minutes and 47 seconds on 2014-04-04 roll = 180.0f / PI;

if(SerialDebug) {
Serial.print("Yaw, Pitch, Roll: ");
Serial.print(yaw, 2);
Serial.print(", ");
Serial.print(pitch, 2);
Serial.print(", ");
Serial.println(roll, 2);

Serial.print("rate = "); Serial.print((float)sumCount/sum, 2); Serial.println(" Hz");
}

// With these settings the filter is updating at a ~145 Hz rate using the Madgwick scheme and
// >200 Hz using the Mahony scheme even though the display refreshes at only 2 Hz.
// The filter update rate is determined mostly by the mathematical steps in the respective algorithms,
// the processor speed (8 MHz for the 3.3V Pro Mini), and the magnetometer ODR:
// an ODR of 10 Hz for the magnetometer produce the above rates, maximum magnetometer ODR of 100 Hz produces
// filter update rates of 36 - 145 and ~38 Hz for the Madgwick and Mahony schemes, respectively.
// This is presumably because the magnetometer read takes longer than the gyro or accelerometer reads.
// This filter update rate should be fast enough to maintain accurate platform orientation for
// stabilization control of a fast-moving robot or quadcopter. Compare to the update rate of 200 Hz
// produced by the on-board Digital Motion Processor of Invensense's MPU6050 6 DoF and MPU9150 9DoF sensors.
// The 3.3 V 8 MHz Pro Mini is doing pretty well!
//display.setCursor(0, 40); display.print("rt: "); display.print((float) sumCount / sum, 2); display.print(" Hz");
//display.display();

digitalWrite(myLed, !digitalRead(myLed));
count = millis();
sumCount = 0;
sum = 0;
}
}

}

//=================================================================================================================== //====== Set of useful function to access acceleration. gyroscope, magnetometer, and temperature data //===================================================================================================================

void getMres() { switch (Mscale) { // Possible magnetometer scales (and their register bit settings) are: // 14 bit resolution (0) and 16 bit resolution (1) case MFS_14BITS: mRes = 10.4912./8190.; // Proper scale to return milliGauss break; case MFS_16BITS: mRes = 10.4912./32760.0; // Proper scale to return milliGauss break; } }

void getGres() { switch (Gscale) { // Possible gyro scales (and their register bit settings) are: // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS (11). // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value: case GFS_250DPS: gRes = 250.0/32768.0; break; case GFS_500DPS: gRes = 500.0/32768.0; break; case GFS_1000DPS: gRes = 1000.0/32768.0; break; case GFS_2000DPS: gRes = 2000.0/32768.0; break; } }

void getAres() { switch (Ascale) { // Possible accelerometer scales (and their register bit settings) are: // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs (11). // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value: case AFS_2G: aRes = 2.0/32768.0; break; case AFS_4G: aRes = 4.0/32768.0; break; case AFS_8G: aRes = 8.0/32768.0; break; case AFS_16G: aRes = 16.0/32768.0; break; } }

void readAccelData(int16_t * destination) { uint8_t rawData[6]; // x/y/z accel register data stored here readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array destination[0] = ((int16_t)rawData[0] << 8) | rawData[1] ; // Turn the MSB and LSB into a signed 16-bit value destination[1] = ((int16_t)rawData[2] << 8) | rawData[3] ; destination[2] = ((int16_t)rawData[4] << 8) | rawData[5] ; }

void readGyroData(int16_t * destination) { uint8_t rawData[6]; // x/y/z gyro register data stored here readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array destination[0] = ((int16_t)rawData[0] << 8) | rawData[1] ; // Turn the MSB and LSB into a signed 16-bit value destination[1] = ((int16_t)rawData[2] << 8) | rawData[3] ; destination[2] = ((int16_t)rawData[4] << 8) | rawData[5] ; }

void readMagData(int16_t * destination) { uint8_t rawData[7]; // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]); // Read the six raw data and ST2 registers sequentially into data array uint8_t c = rawData[6]; // End data read by reading ST2 register if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data destination[0] = ((int16_t)rawData[1] << 8) | rawData[0] ; // Turn the MSB and LSB into a signed 16-bit value destination[1] = ((int16_t)rawData[3] << 8) | rawData[2] ; // Data stored as little Endian destination[2] = ((int16_t)rawData[5] << 8) | rawData[4] ; } } }

int16_t readTempData() { uint8_t rawData[2]; // x/y/z gyro register data stored here readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]); // Read the two raw data registers sequentially into data array return ((int16_t)rawData[0] << 8) | rawData[1] ; // Turn the MSB and LSB into a 16-bit value }

void initAK8963(float * destination) { // First extract the factory calibration for each magnetometer axis uint8_t rawData[3]; // x/y/z gyro calibration data stored here writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer delay(10); writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode delay(10); readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]); // Read the x-, y-, and z-axis calibration values destination[0] = (float)(rawData[0] - 128)/256. + 1.; // Return x-axis sensitivity adjustment values, etc. destination[1] = (float)(rawData[1] - 128)/256. + 1.; destination[2] = (float)(rawData[2] - 128)/256. + 1.; writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer delay(10); // Configure the magnetometer for continuous read and highest resolution // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register, // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR delay(10); }

void initMPU9250() { // wake up device writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors delay(100); // Wait for all registers to reset

// get stable time source writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01); // Auto select clock source to be PLL gyroscope reference if ready else delay(200);

// Configure Gyro and Thermometer // Disable FSYNC and set thermometer and gyro bandwidth to 41 and 42 Hz, respectively; // minimum delay time for this setting is 5.9 ms, which means sensor fusion update rates cannot // be higher than 1 / 0.0059 = 170 Hz // DLPF_CFG = bits 2:0 = 011; this limits the sample rate to 1000 Hz for both // With the MPU9250, it is possible to get gyro sample rates of 32 kHz (!), 8 kHz, or 1 kHz writeByte(MPU9250_ADDRESS, CONFIG, 0x03);

// Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV) writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04); // Use a 200 Hz rate; a rate consistent with the filter update rate // determined inset in CONFIG above

// Set gyroscope full scale range // Range selects FS_SEL and GFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3 uint8_t c = readByte(MPU9250_ADDRESS, GYRO_CONFIG); // get current GYRO_CONFIG register value // c = c & ~0xE0; // Clear self-test bits [7:5] c = c & ~0x03; // Clear Fchoice bits [1:0] c = c & ~0x18; // Clear GFS bits [4:3] c = c | Gscale << 3; // Set full scale range for the gyro // c =| 0x00; // Set Fchoice for the gyro to 11 by writing its inverse to bits 1:0 of GYRO_CONFIG writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c ); // Write new GYRO_CONFIG value to register

// Set accelerometer full-scale range configuration c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG); // get current ACCEL_CONFIG register value // c = c & ~0xE0; // Clear self-test bits [7:5] c = c & ~0x18; // Clear AFS bits [4:3] c = c | Ascale << 3; // Set full scale range for the accelerometer writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c); // Write new ACCEL_CONFIG register value

// Set accelerometer sample rate configuration // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2); // get current ACCEL_CONFIG2 register value c = c & ~0x0F; // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0]) c = c | 0x03; // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c); // Write new ACCEL_CONFIG2 register value

// The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting

// Configure Interrupts and Bypass Enable // Set interrupt pin active high, push-pull, hold interrupt pin level HIGH until interrupt cleared, // clear on read of INT_STATUS, and enable I2C_BYPASS_EN so additional chips // can join the I2C bus and all can be controlled by the Arduino as master //writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22); writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x12); writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01); // Enable data ready (bit 0) interrupt delay(100); }

// Function which accumulates gyro and accelerometer data after device initialization. It calculates the average // of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers. void calibrateMPU9250(float dest1, float dest2) { uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data uint16_t ii, packet_count, fifo_count; int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};

// reset device writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device delay(100);

// get stable time source; Auto select clock source to be PLL gyroscope reference if ready // else use the internal oscillator, bits 2:0 = 001 writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01); writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00); delay(200);

// Configure device for bias calculation writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00); // Disable all interrupts writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00); // Disable FIFO writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Turn on internal clock source writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00); // Disable FIFO and I2C master modes writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C); // Reset FIFO and DMP delay(15);

// Configure MPU6050 gyro and accelerometer for bias calculation writeByte(MPU9250_ADDRESS, CONFIG, 0x01); // Set low-pass filter to 188 Hz writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set sample rate to 1 kHz writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00); // Set gyro full-scale to 250 degrees per second, maximum sensitivity writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity

uint16_t gyrosensitivity = 131; // = 131 LSB/degrees/sec uint16_t accelsensitivity = 16384; // = 16384 LSB/g

// Configure FIFO to capture accelerometer and gyro data for bias calculation

writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40); // Enable FIFO writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78); // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9150) delay(40); // accumulate 40 samples in 40 milliseconds = 480 bytes

// At end of sample accumulation, turn off FIFO sensor read writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00); // Disable gyro and accelerometer sensors for FIFO readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count fifo_count = ((uint16_t)data[0] << 8) | data[1]; packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging

for (ii = 0; ii < packet_count; ii++) { int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0}; readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1] ) ; // Form signed 16-bit integer for each sample in FIFO accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3] ) ; accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5] ) ; gyro_temp[0] = (int16_t) (((int16_t)data[6] << 8) | data[7] ) ; gyro_temp[1] = (int16_t) (((int16_t)data[8] << 8) | data[9] ) ; gyro_temp[2] = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;

accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
accel_bias[1] += (int32_t) accel_temp[1];
accel_bias[2] += (int32_t) accel_temp[2];
gyro_bias[0]  += (int32_t) gyro_temp[0];
gyro_bias[1]  += (int32_t) gyro_temp[1];
gyro_bias[2]  += (int32_t) gyro_temp[2];

} accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases accel_bias[1] /= (int32_t) packet_count; accel_bias[2] /= (int32_t) packet_count; gyro_bias[0] /= (int32_t) packet_count; gyro_bias[1] /= (int32_t) packet_count; gyro_bias[2] /= (int32_t) packet_count;

if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;} // Remove gravity from the z-axis accelerometer bias calculation else {accel_bias[2] += (int32_t) accelsensitivity;}

// Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup data[0] = (-gyro_bias[0]/4 >> 8) & 0xFF; // Divide by 4 to get 32.9 LSB per deg/s to conform to expected bias input format data[1] = (-gyro_bias[0]/4) & 0xFF; // Biases are additive, so change sign on calculated average gyro biases data[2] = (-gyro_bias[1]/4 >> 8) & 0xFF; data[3] = (-gyro_bias[1]/4) & 0xFF; data[4] = (-gyro_bias[2]/4 >> 8) & 0xFF; data[5] = (-gyro_bias[2]/4) & 0xFF;

// Push gyro biases to hardware registers writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]); writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]); writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]); writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]); writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]); writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);

// Output scaled gyro biases for display in the main program dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity; dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;

// Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain // factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold // non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature // compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that // the accelerometer biases calculated above must be divided by 8.

int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values accel_bias_reg[0] = (int32_t) (((int16_t)data[0] << 8) | data[1]); readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]); accel_bias_reg[1] = (int32_t) (((int16_t)data[0] << 8) | data[1]); readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]); accel_bias_reg[2] = (int32_t) (((int16_t)data[0] << 8) | data[1]);

uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis

for(ii = 0; ii < 3; ii++) { if((accel_bias_reg[ii] & mask)) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit }

// Construct total accelerometer bias, including calculated average accelerometer bias from above accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale) accel_bias_reg[1] -= (accel_bias[1]/8); accel_bias_reg[2] -= (accel_bias[2]/8);

data[0] = (accel_bias_reg[0] >> 8) & 0xFF; data[1] = (accel_bias_reg[0]) & 0xFF; data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers data[2] = (accel_bias_reg[1] >> 8) & 0xFF; data[3] = (accel_bias_reg[1]) & 0xFF; data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers data[4] = (accel_bias_reg[2] >> 8) & 0xFF; data[5] = (accel_bias_reg[2]) & 0xFF; data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers

// Apparently this is not working for the acceleration biases in the MPU-9250 // Are we handling the temperature correction bit properly? // Push accelerometer biases to hardware registers writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]); writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]); writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]); writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]); writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]); writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);

// Output scaled accelerometer biases for display in the main program dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; dest2[1] = (float)accel_bias[1]/(float)accelsensitivity; dest2[2] = (float)accel_bias[2]/(float)accelsensitivity; }

// Accelerometer and gyroscope self test; check calibration wrt factory settings void MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass { uint8_t rawData[6] = {0, 0, 0, 0, 0, 0}; uint8_t selfTest[6]; int32_t gAvg[3] = {0}, aAvg[3] = {0}, aSTAvg[3] = {0}, gSTAvg[3] = {0}; float factoryTrim[6]; uint8_t FS = 0;

writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz writeByte(MPU9250_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz writeByte(MPU9250_ADDRESS, GYRO_CONFIG, FS<<3); // Set full scale range for the gyro to 250 dps writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, FS<<3); // Set full scale range for the accelerometer to 2 g

for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer

readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;

readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);       // Read the six raw data registers sequentially into data array

gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; }

for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average current readings aAvg[ii] /= 200; gAvg[ii] /= 200; }

// Configure the accelerometer for self-test writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s delay(25); // Delay a while to let the device stabilize

for( int ii = 0; ii < 200; ii++) { // get average self-test values of gyro and acclerometer

readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;

readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array

gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ; gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; }

for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average self-test readings aSTAvg[ii] /= 200; gSTAvg[ii] /= 200; }

// Configure the gyro and accelerometer for normal operation writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00); delay(25); // Delay a while to let the device stabilize

// Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results

// Retrieve factory self-test value from self-test code reads factoryTrim[0] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation factoryTrim[1] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation factoryTrim[2] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation factoryTrim[3] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation factoryTrim[4] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation factoryTrim[5] = (float)(2620/1<<FS)(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation

// Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response // To get percent, must multiply by 100 for (int i = 0; i < 3; i++) { destination[i] = 100.0((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i] - 100.; // Report percent differences destination[i+3] = 100.0((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3] - 100.; // Report percent differences }

}

// I2C read/write functions for the MPU9250 and AK8963 sensors

    void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)

{ Wire.beginTransmission(address); // Initialize the Tx buffer Wire.write(subAddress); // Put slave register address in Tx buffer Wire.write(data); // Put data in Tx buffer Wire.endTransmission(); // Send the Tx buffer }

    uint8_t readByte(uint8_t address, uint8_t subAddress)

{ uint8_t data; // data will store the register data Wire.beginTransmission(address); // Initialize the Tx buffer Wire.write(subAddress); // Put slave register address in Tx buffer Wire.endTransmission(); // Send the Tx buffer, but send a restart to keep connection alive // Wire.endTransmission(false); // Send the Tx buffer, but send a restart to keep connection alive // Wire.requestFrom(address, 1); // Read one byte from slave register address Wire.requestFrom(address, (size_t) 1); // Read one byte from slave register address data = Wire.read(); // Fill Rx buffer with result return data; // Return data read from slave register }

    void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)

{ Wire.beginTransmission(address); // Initialize the Tx buffer Wire.write(subAddress); // Put slave register address in Tx buffer Wire.endTransmission(); // Send the Tx buffer, but send a restart to keep connection alive // Wire.endTransmission(false); // Send the Tx buffer, but send a restart to keep connection alive uint8_t i = 0; // Wire.requestFrom(address, count); // Read bytes from slave register address Wire.requestFrom(address, (size_t) count); // Read bytes from slave register address while (Wire.available()) { dest[i++] = Wire.read(); } // Put read results in the Rx buffer }

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[mjs513]

Hi Kris - just used your basic version from GitHub. No particular reason why I picked that one. Which version should I use?

For the mag want to update the final version to use to check the mag data ready register instead of doing the way I am doing it now.? In the mean time I will go poking around. I went to eye doctor this morning and my eyes are still all out of sort so this should be fun :) Will keep you posted

EDIT: Just was looking at all your 9250 sketches and they seem to use the same base code as I just posted. Let me play with the code.

OK - going to use the esp32 code as the base for testing.

[kriswiner]

Maybe start here: https://github.com/kriswiner/MPU9250/tree/master/AK8963_as_slave

On Tue, Nov 13, 2018 at 10:52 AM Mike S notifications@github.com wrote:

Hi Kris - just used your basic version from GitHub. No particular reason why I picked that one. Which version should I use?

For the mag want to update the final version to use to check the mag data ready register instead of doing the way I am doing it now.? In the mean time I will go poking around. I went to eye doctor this morning and my eyes are still all out of sort so this should be fun :) Will keep you posted

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[mjs513]

Hi Kris, Will definitely take a look. Any I did mod your esp32 sketch to run on the T3.5 since it had the interrupt configured as a data ready interrupt as well as the code for the mag data ready test. I also had the 10x loop for the filter set up properly. It also did the cal's for the accel, gyro and magnetometer and the reads of the accel/gyro at one time :) So basically it did what you suggested in the earlier post.

Any way, whether I used a clock freq of 400k or 1000khz I got a rate of about 2khz for the T5 at 120Mhz overclock. Does this sound about right?

[kriswiner]

No, it really should be higher unless you are liiting the iterations of the fusion filter to ten or so.

On Tue, Nov 13, 2018 at 11:55 AM Mike S notifications@github.com wrote:

Hi Kris, Will definitely take a look. Any I did mod your esp32 sketch to run on the T3.5 since it had the interrupt configured as a data ready interrupt as well as the code for the mag data ready test. I also had the 10x loop for the filter set up properly. It also did the cal's for the accel, gyro and magnetometer and the reads of the accel/gyro at one time :) So basically it did what you suggested in the earlier post.

Any way, whether I used a clock freq of 400k or 1000khz I got a rate of about 2khz for the T5 at 120Mhz overclock. Does this sound about right?

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[mjs513]

Right now its set to 10, matches what you have in the esp32 sketch. Got it ported over to the imrtx1050 and its giving me 1951hz. a little lower than for the T3.5.

EDIT: I increased the loop count from 10 to 40 and got up to 7810 Hz. So the question that now comes to mind is what is a good comparison count to use for performance of the mcu's? or should I do a completely different comparison? Don't know?

[kriswiner]

This is what I would expect. At 1 MHz bus speed should jump to 4 kHz.

On Tue, Nov 13, 2018 at 2:50 PM Mike S notifications@github.com wrote:

Right now its set to 10, matches what you have in the esp32 sketch. Got it ported over to the imrtx1050 and its giving me 1951hz. a little lower than for the T3.5.

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