Pre-test

Dependencies:   LinkedList mbed-rtos mbed

Files at this revision

API Documentation at this revision

Comitter:
Khanchana
Date:
Mon Apr 09 15:57:36 2018 +0000
Commit message:
Pre-test

Changed in this revision

LinkedList.lib Show annotated file Show diff for this revision Revisions of this file
MPU9250.h Show annotated file Show diff for this revision Revisions of this file
attitude.h Show annotated file Show diff for this revision Revisions of this file
main.cpp Show annotated file Show diff for this revision Revisions of this file
mbed-rtos.lib Show annotated file Show diff for this revision Revisions of this file
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diff -r 000000000000 -r d98bd8b7dc46 LinkedList.lib
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/LinkedList.lib	Mon Apr 09 15:57:36 2018 +0000
@@ -0,0 +1,1 @@
+http://os.mbed.com/users/sam_grove/code/LinkedList/#4ed66162aaa8
diff -r 000000000000 -r d98bd8b7dc46 MPU9250.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MPU9250.h	Mon Apr 09 15:57:36 2018 +0000
@@ -0,0 +1,874 @@
+#ifndef MPU9250_H
+#define MPU9250_H
+ 
+#include "mbed.h"
+#include "math.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<<1
+#define WHO_AM_I_AK8963  0x00 // should return 0x48
+#define 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
+//mbed uses the eight-bit device address, so shift seven-bit addresses left by one!
+#define ADO 0
+#if ADO
+#define MPU9250_ADDRESS 0x69<<1  // Device address when ADO = 1
+#else
+#define MPU9250_ADDRESS 0x68<<1  // Device address when ADO = 0
+#endif  
+
+// 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
+};
+
+uint8_t Ascale = AFS_2G;     // AFS_2G, AFS_4G, AFS_8G, AFS_16G
+uint8_t Gscale = GFS_250DPS; // GFS_250DPS, GFS_500DPS, GFS_1000DPS, GFS_2000DPS
+uint8_t Mscale = MFS_16BITS; // MFS_14BITS or MFS_16BITS, 14-bit or 16-bit magnetometer resolution
+uint8_t Mmode = 0x06;        // Either 8 Hz 0x02) or 100 Hz (0x06) magnetometer data ODR  
+float aRes, gRes, mRes;      // scale resolutions per LSB for the sensors
+
+//Set up I2C, (SDA,SCL)
+I2C i2c(I2C_SDA, I2C_SCL);
+
+DigitalOut myled(LED1);
+    
+// Pin definitions
+int intPin = 12;  // These can be changed, 2 and 3 are the Arduinos ext int pins
+
+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
+float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values 
+int16_t tempCount;   // Stores the real internal chip temperature in degrees Celsius
+float temperature;
+float SelfTest[6];
+
+int delt_t = 0; // used to control display output rate
+int count = 0;  // used to control display output rate
+
+// parameters for 6 DoF sensor fusion calculations
+float PI = 3.14159265358979323846f;
+float GyroMeasError = PI * (60.0f / 180.0f);     // gyroscope measurement error in rads/s (start at 60 deg/s), then reduce after ~10 s to 3
+float beta = sqrt(3.0f / 4.0f) * GyroMeasError;  // compute beta
+float GyroMeasDrift = PI * (1.0f / 180.0f);      // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s)
+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
+
+float pitch, yaw, roll;
+float deltat = 0.0f;                             // integration interval for both filter schemes
+int lastUpdate = 0, firstUpdate = 0, Now = 0;    // used to calculate integration interval                               // used to calculate integration interval
+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
+
+class MPU9250 {
+ 
+    protected:
+ 
+    public:
+  //===================================================================================================================
+//====== Set of useful function to access acceleratio, gyroscope, and temperature data
+//===================================================================================================================
+
+    void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
+{
+   char data_write[2];
+   data_write[0] = subAddress;
+   data_write[1] = data;
+   i2c.write(address, data_write, 2, 0);
+}
+
+    char readByte(uint8_t address, uint8_t subAddress)
+{
+    char data[1]; // `data` will store the register data     
+    char data_write[1];
+    data_write[0] = subAddress;
+    i2c.write(address, data_write, 1, 1); // no stop
+    i2c.read(address, data, 1, 0); 
+    return data[0]; 
+}
+
+    void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
+{     
+    char data[14];
+    char data_write[1];
+    data_write[0] = subAddress;
+    i2c.write(address, data_write, 1, 1); // no stop
+    i2c.read(address, data, count, 0); 
+    for(int ii = 0; ii < count; ii++) {
+     dest[ii] = data[ii];
+    }
+} 
+ 
+
+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 = 10.0*4219.0/8190.0; // Proper scale to return milliGauss
+          break;
+    case MFS_16BITS:
+          mRes = 10.0*4219.0/32760.0; // 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)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
+  destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
+  destination[2] = (int16_t)(((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)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
+  destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
+  destination[2] = (int16_t)(((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)(((int16_t)rawData[1] << 8) | rawData[0]);  // Turn the MSB and LSB into a signed 16-bit value
+    destination[1] = (int16_t)(((int16_t)rawData[3] << 8) | rawData[2]) ;  // Data stored as little Endian
+    destination[2] = (int16_t)(((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)(((int16_t)rawData[0]) << 8 | rawData[1]) ;  // Turn the MSB and LSB into a 16-bit value
+}
+
+
+void resetMPU9250() {
+  // reset device
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
+  wait(0.1);
+  }
+  
+  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  
+  wait(0.01);
+  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode
+  wait(0.01);
+  readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
+  destination[0] =  (float)(rawData[0] - 128)/256.0f + 1.0f;   // Return x-axis sensitivity adjustment values, etc.
+  destination[1] =  (float)(rawData[1] - 128)/256.0f + 1.0f;  
+  destination[2] =  (float)(rawData[2] - 128)/256.0f + 1.0f; 
+  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
+  wait(0.01);
+  // 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
+  wait(0.01);
+}
+
+
+void initMPU9250()
+{  
+ // Initialize MPU9250 device
+ // wake up device
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors 
+  wait(0.1); // Delay 100 ms for PLL to get established on x-axis gyro; should check for PLL ready interrupt  
+
+ // get stable time source
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
+
+ // Configure Gyro and Accelerometer
+ // Disable FSYNC and set accelerometer and gyro bandwidth to 44 and 42 Hz, respectively; 
+ // DLPF_CFG = bits 2:0 = 010; this sets the sample rate at 1 kHz for both
+ // Maximum delay is 4.9 ms which is just over a 200 Hz maximum rate
+  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; the same rate set in CONFIG above
+ 
+ // Set gyroscope full scale range
+ // Range selects FS_SEL and AFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
+  uint8_t c =  readByte(MPU9250_ADDRESS, GYRO_CONFIG);
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0xE0); // Clear self-test bits [7:5] 
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c | Gscale << 3); // Set full scale range for the gyro
+   
+ // Set accelerometer configuration
+  c =  readByte(MPU9250_ADDRESS, ACCEL_CONFIG);
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0xE0); // Clear self-test bits [7:5] 
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c | Ascale << 3); // Set full scale range for the accelerometer 
+
+ // 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);
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c & ~0x0F); // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])  
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c | 0x03); // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
+
+ // 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, and clear on read of INT_STATUS, 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_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
+}
+
+// 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, reset all registers, clear gyro and accelerometer bias registers
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
+  wait(0.1);  
+   
+// get stable time source
+// Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00); 
+  wait(0.2);
+  
+// 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
+  wait(0.015);
+  
+// Configure MPU9250 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-9250)
+  wait(0.04); // accumulate 40 samples in 80 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]);
+*/
+  dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; // construct gyro bias in deg/s for later manual subtraction
+  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] = (int16_t) ((int16_t)data[0] << 8) | data[1];
+  readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]);
+  accel_bias_reg[1] = (int16_t) ((int16_t)data[0] << 8) | data[1];
+  readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
+  accel_bias_reg[2] = (int16_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 manual subtraction 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];
+   int16_t gAvg[3], aAvg[3], aSTAvg[3], gSTAvg[3];
+   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, 1<<FS); // 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, 1<<FS); // 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
+   wait_ms(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);
+   wait_ms(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]; // Report percent differences
+     destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3]; // Report percent differences
+   }
+   
+}
+
+
+
+// Implementation of Sebastian Madgwick's "...efficient orientation filter for... inertial/magnetic sensor arrays"
+// (see http://www.x-io.co.uk/category/open-source/ for examples and more details)
+// which fuses acceleration, rotation rate, and magnetic moments to produce a quaternion-based estimate of absolute
+// device orientation -- which can be converted to yaw, pitch, and roll. Useful for stabilizing quadcopters, etc.
+// The performance of the orientation filter is at least as good as conventional Kalman-based filtering algorithms
+// but is much less computationally intensive---it can be performed on a 3.3 V Pro Mini operating at 8 MHz!
+        void MadgwickQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
+        {
+            float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
+            float norm;
+            float hx, hy, _2bx, _2bz;
+            float s1, s2, s3, s4;
+            float qDot1, qDot2, qDot3, qDot4;
+
+            // Auxiliary variables to avoid repeated arithmetic
+            float _2q1mx;
+            float _2q1my;
+            float _2q1mz;
+            float _2q2mx;
+            float _4bx;
+            float _4bz;
+            float _2q1 = 2.0f * q1;
+            float _2q2 = 2.0f * q2;
+            float _2q3 = 2.0f * q3;
+            float _2q4 = 2.0f * q4;
+            float _2q1q3 = 2.0f * q1 * q3;
+            float _2q3q4 = 2.0f * q3 * q4;
+            float q1q1 = q1 * q1;
+            float q1q2 = q1 * q2;
+            float q1q3 = q1 * q3;
+            float q1q4 = q1 * q4;
+            float q2q2 = q2 * q2;
+            float q2q3 = q2 * q3;
+            float q2q4 = q2 * q4;
+            float q3q3 = q3 * q3;
+            float q3q4 = q3 * q4;
+            float q4q4 = q4 * q4;
+
+            // Normalise accelerometer measurement
+            norm = sqrt(ax * ax + ay * ay + az * az);
+            if (norm == 0.0f) return; // handle NaN
+            norm = 1.0f/norm;
+            ax *= norm;
+            ay *= norm;
+            az *= norm;
+
+            // Normalise magnetometer measurement
+            norm = sqrt(mx * mx + my * my + mz * mz);
+            if (norm == 0.0f) return; // handle NaN
+            norm = 1.0f/norm;
+            mx *= norm;
+            my *= norm;
+            mz *= norm;
+
+            // Reference direction of Earth's magnetic field
+            _2q1mx = 2.0f * q1 * mx;
+            _2q1my = 2.0f * q1 * my;
+            _2q1mz = 2.0f * q1 * mz;
+            _2q2mx = 2.0f * q2 * mx;
+            hx = mx * q1q1 - _2q1my * q4 + _2q1mz * q3 + mx * q2q2 + _2q2 * my * q3 + _2q2 * mz * q4 - mx * q3q3 - mx * q4q4;
+            hy = _2q1mx * q4 + my * q1q1 - _2q1mz * q2 + _2q2mx * q3 - my * q2q2 + my * q3q3 + _2q3 * mz * q4 - my * q4q4;
+            _2bx = sqrt(hx * hx + hy * hy);
+            _2bz = -_2q1mx * q3 + _2q1my * q2 + mz * q1q1 + _2q2mx * q4 - mz * q2q2 + _2q3 * my * q4 - mz * q3q3 + mz * q4q4;
+            _4bx = 2.0f * _2bx;
+            _4bz = 2.0f * _2bz;
+
+            // Gradient decent algorithm corrective step
+            s1 = -_2q3 * (2.0f * q2q4 - _2q1q3 - ax) + _2q2 * (2.0f * q1q2 + _2q3q4 - ay) - _2bz * q3 * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (-_2bx * q4 + _2bz * q2) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + _2bx * q3 * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
+            s2 = _2q4 * (2.0f * q2q4 - _2q1q3 - ax) + _2q1 * (2.0f * q1q2 + _2q3q4 - ay) - 4.0f * q2 * (1.0f - 2.0f * q2q2 - 2.0f * q3q3 - az) + _2bz * q4 * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (_2bx * q3 + _2bz * q1) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + (_2bx * q4 - _4bz * q2) * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
+            s3 = -_2q1 * (2.0f * q2q4 - _2q1q3 - ax) + _2q4 * (2.0f * q1q2 + _2q3q4 - ay) - 4.0f * q3 * (1.0f - 2.0f * q2q2 - 2.0f * q3q3 - az) + (-_4bx * q3 - _2bz * q1) * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (_2bx * q2 + _2bz * q4) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + (_2bx * q1 - _4bz * q3) * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
+            s4 = _2q2 * (2.0f * q2q4 - _2q1q3 - ax) + _2q3 * (2.0f * q1q2 + _2q3q4 - ay) + (-_4bx * q4 + _2bz * q2) * (_2bx * (0.5f - q3q3 - q4q4) + _2bz * (q2q4 - q1q3) - mx) + (-_2bx * q1 + _2bz * q3) * (_2bx * (q2q3 - q1q4) + _2bz * (q1q2 + q3q4) - my) + _2bx * q2 * (_2bx * (q1q3 + q2q4) + _2bz * (0.5f - q2q2 - q3q3) - mz);
+            norm = sqrt(s1 * s1 + s2 * s2 + s3 * s3 + s4 * s4);    // normalise step magnitude
+            norm = 1.0f/norm;
+            s1 *= norm;
+            s2 *= norm;
+            s3 *= norm;
+            s4 *= norm;
+
+            // Compute rate of change of quaternion
+            qDot1 = 0.5f * (-q2 * gx - q3 * gy - q4 * gz) - beta * s1;
+            qDot2 = 0.5f * (q1 * gx + q3 * gz - q4 * gy) - beta * s2;
+            qDot3 = 0.5f * (q1 * gy - q2 * gz + q4 * gx) - beta * s3;
+            qDot4 = 0.5f * (q1 * gz + q2 * gy - q3 * gx) - beta * s4;
+
+            // Integrate to yield quaternion
+            q1 += qDot1 * deltat;
+            q2 += qDot2 * deltat;
+            q3 += qDot3 * deltat;
+            q4 += qDot4 * deltat;
+            norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);    // normalise quaternion
+            norm = 1.0f/norm;
+            q[0] = q1 * norm;
+            q[1] = q2 * norm;
+            q[2] = q3 * norm;
+            q[3] = q4 * norm;
+
+        }
+  
+  
+  
+ // Similar to Madgwick scheme but uses proportional and integral filtering on the error between estimated reference vectors and
+ // measured ones. 
+            void MahonyQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
+        {
+            float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
+            float norm;
+            float hx, hy, bx, bz;
+            float vx, vy, vz, wx, wy, wz;
+            float ex, ey, ez;
+            float pa, pb, pc;
+
+            // Auxiliary variables to avoid repeated arithmetic
+            float q1q1 = q1 * q1;
+            float q1q2 = q1 * q2;
+            float q1q3 = q1 * q3;
+            float q1q4 = q1 * q4;
+            float q2q2 = q2 * q2;
+            float q2q3 = q2 * q3;
+            float q2q4 = q2 * q4;
+            float q3q3 = q3 * q3;
+            float q3q4 = q3 * q4;
+            float q4q4 = q4 * q4;   
+
+            // Normalise accelerometer measurement
+            norm = sqrt(ax * ax + ay * ay + az * az);
+            if (norm == 0.0f) return; // handle NaN
+            norm = 1.0f / norm;        // use reciprocal for division
+            ax *= norm;
+            ay *= norm;
+            az *= norm;
+
+            // Normalise magnetometer measurement
+            norm = sqrt(mx * mx + my * my + mz * mz);
+            if (norm == 0.0f) return; // handle NaN
+            norm = 1.0f / norm;        // use reciprocal for division
+            mx *= norm;
+            my *= norm;
+            mz *= norm;
+
+            // Reference direction of Earth's magnetic field
+            hx = 2.0f * mx * (0.5f - q3q3 - q4q4) + 2.0f * my * (q2q3 - q1q4) + 2.0f * mz * (q2q4 + q1q3);
+            hy = 2.0f * mx * (q2q3 + q1q4) + 2.0f * my * (0.5f - q2q2 - q4q4) + 2.0f * mz * (q3q4 - q1q2);
+            bx = sqrt((hx * hx) + (hy * hy));
+            bz = 2.0f * mx * (q2q4 - q1q3) + 2.0f * my * (q3q4 + q1q2) + 2.0f * mz * (0.5f - q2q2 - q3q3);
+
+            // Estimated direction of gravity and magnetic field
+            vx = 2.0f * (q2q4 - q1q3);
+            vy = 2.0f * (q1q2 + q3q4);
+            vz = q1q1 - q2q2 - q3q3 + q4q4;
+            wx = 2.0f * bx * (0.5f - q3q3 - q4q4) + 2.0f * bz * (q2q4 - q1q3);
+            wy = 2.0f * bx * (q2q3 - q1q4) + 2.0f * bz * (q1q2 + q3q4);
+            wz = 2.0f * bx * (q1q3 + q2q4) + 2.0f * bz * (0.5f - q2q2 - q3q3);  
+
+            // Error is cross product between estimated direction and measured direction of gravity
+            ex = (ay * vz - az * vy) + (my * wz - mz * wy);
+            ey = (az * vx - ax * vz) + (mz * wx - mx * wz);
+            ez = (ax * vy - ay * vx) + (mx * wy - my * wx);
+            if (Ki > 0.0f)
+            {
+                eInt[0] += ex;      // accumulate integral error
+                eInt[1] += ey;
+                eInt[2] += ez;
+            }
+            else
+            {
+                eInt[0] = 0.0f;     // prevent integral wind up
+                eInt[1] = 0.0f;
+                eInt[2] = 0.0f;
+            }
+
+            // Apply feedback terms
+            gx = gx + Kp * ex + Ki * eInt[0];
+            gy = gy + Kp * ey + Ki * eInt[1];
+            gz = gz + Kp * ez + Ki * eInt[2];
+
+            // Integrate rate of change of quaternion
+            pa = q2;
+            pb = q3;
+            pc = q4;
+            q1 = q1 + (-q2 * gx - q3 * gy - q4 * gz) * (0.5f * deltat);
+            q2 = pa + (q1 * gx + pb * gz - pc * gy) * (0.5f * deltat);
+            q3 = pb + (q1 * gy - pa * gz + pc * gx) * (0.5f * deltat);
+            q4 = pc + (q1 * gz + pa * gy - pb * gx) * (0.5f * deltat);
+
+            // Normalise quaternion
+            norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);
+            norm = 1.0f / norm;
+            q[0] = q1 * norm;
+            q[1] = q2 * norm;
+            q[2] = q3 * norm;
+            q[3] = q4 * norm;
+ 
+        }
+  };
+#endif
\ No newline at end of file
diff -r 000000000000 -r d98bd8b7dc46 attitude.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/attitude.h	Mon Apr 09 15:57:36 2018 +0000
@@ -0,0 +1,81 @@
+#include "MPU9250.h"
+
+MPU9250 mpu9250;
+
+Timer t;
+
+void attitude_setup(void)
+{
+    i2c.frequency(400000);  // use fast (400 kHz) I2C
+    
+    t.start();
+
+    // Read the WHO_AM_I register, this is a good test of communication
+    uint8_t whoami = mpu9250.readByte(MPU9250_ADDRESS, WHO_AM_I_MPU9250);  // Read WHO_AM_I register for MPU-9250
+    
+
+    if (whoami == 0x73) { // WHO_AM_I should always be 0x68
+        wait(1);
+        mpu9250.resetMPU9250(); // Reset registers to default in preparation for device calibration
+        mpu9250.calibrateMPU9250(gyroBias, accelBias); // Calibrate gyro and accelerometers, load biases in bias registers
+        wait(2);
+        mpu9250.initMPU9250();
+        mpu9250.initAK8963(magCalibration);
+        wait(2);
+    } else while(1) ; // Loop forever if communication doesn't happen
+
+    mpu9250.getAres(); // Get accelerometer sensitivity
+    mpu9250.getGres(); // Get gyro sensitivity
+    mpu9250.getMres(); // Get magnetometer sensitivity
+
+    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
+}
+
+int attitude_get(void)
+{
+    // If intPin goes high, all data registers have new data
+    if(mpu9250.readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01) {  // On interrupt, check if data ready interrupt
+
+        mpu9250.readAccelData(accelCount);  // Read the x/y/z adc values
+        // Now we'll calculate the accleration value into actual g's
+        ax = (float)accelCount[0]*aRes - accelBias[0];  // get actual g value, this depends on scale being set
+        ay = (float)accelCount[1]*aRes - accelBias[1];
+        az = (float)accelCount[2]*aRes - accelBias[2];
+
+        mpu9250.readGyroData(gyroCount);  // Read the x/y/z adc values
+        // Calculate the gyro value into actual degrees per second
+        gx = (float)gyroCount[0]*gRes - gyroBias[0];  // get actual gyro value, this depends on scale being set
+        gy = (float)gyroCount[1]*gRes - gyroBias[1];
+        gz = (float)gyroCount[2]*gRes - gyroBias[2];
+
+        mpu9250.readMagData(magCount);  // Read the x/y/z adc values
+        // Calculate the magnetometer values in milliGauss
+        // Include factory calibration per data sheet and user environmental corrections
+        mx = (float)magCount[0]*mRes*magCalibration[0] - magbias[0];  // get actual magnetometer value, this depends on scale being set
+        my = (float)magCount[1]*mRes*magCalibration[1] - magbias[1];
+        mz = (float)magCount[2]*mRes*magCalibration[2] - magbias[2];
+
+
+        Now = t.read_us();
+        deltat = (float)((Now - lastUpdate)/1000000.0f) ; // set integration time by time elapsed since last filter update
+        lastUpdate = Now;
+
+        // Pass gyro rate as rad/s
+        mpu9250.MadgwickQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f,  my,  mx, mz);
+        mpu9250.MahonyQuaternionUpdate(ax, ay, az, gx*PI/180.0f, gy*PI/180.0f, gz*PI/180.0f, my, mx, mz);
+
+        yaw   = atan2(2.0f * (q[1] * q[2] + q[0] * q[3]), q[0] * q[0] + q[1] * q[1] - q[2] * q[2] - q[3] * q[3]);
+        pitch = -asin(2.0f * (q[1] * q[3] - q[0] * q[2]));
+        roll  = atan2(2.0f * (q[0] * q[1] + q[2] * q[3]), q[0] * q[0] - q[1] * q[1] - q[2] * q[2] + q[3] * q[3]);
+        pitch *= 180.0f / PI;
+        yaw   *= 180.0f / PI;
+        yaw   -= 13.8f; // Declination at Danville, California is 13 degrees 48 minutes and 47 seconds on 2014-04-04
+        roll  *= 180.0f / PI;
+
+        return 0;
+    }
+    return -1;
+}
+
diff -r 000000000000 -r d98bd8b7dc46 main.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Apr 09 15:57:36 2018 +0000
@@ -0,0 +1,63 @@
+#include "mbed.h"
+#include "rtos.h"
+#include "attitude.h"
+#include "LinkedList.h"
+  
+LinkedList<int>command;
+
+Serial pc(USBTX,USBRX);
+
+Timer timer1; 
+Timer timerwalk;
+
+Thread thread1;
+Thread thread2;
+
+void IMU();
+void move();
+
+int walking_time;
+int i = 1;
+int n = 0;
+
+list<int> command;
+
+int main() {
+    pc.baud(1000000);
+    timer1.start();
+    pc.printf("start\n");
+    thread1.start(move);
+    thread2.start(IMU);
+}
+
+void move(){
+    wait(5);
+    while(n<10){
+        wait(0.01);
+        pc.printf("%d\n", command(n));
+        n = n+1;
+    }
+}
+
+void IMU()
+{
+    while(1) {
+        if (timer1.read_us() >= 1000)// read time in ms
+        {
+            attitude_get();
+            //pc.printf("IMU");
+            //pc.printf(" %f \n", ax*10 ); 
+            //pc.printf("  %f \t", ay*10 ); 
+            //pc.printf("  %f \t", az*10 -10); //cm/s*s
+
+            //pc.printf(" %f \t", gx ); 
+            //pc.printf("  %f \t", gy );  
+            //pc.printf("  %f  \t", gz );  //deg/s    */
+            //pc.printf("%.0f\t  %.0f \t  %.0f \n\r",  roll,   pitch, yaw);
+            command(i) = roll;
+            i = i+1;
+            timer1.reset(); // reset timer 
+        }
+    }
+}
+
diff -r 000000000000 -r d98bd8b7dc46 mbed-rtos.lib
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-rtos.lib	Mon Apr 09 15:57:36 2018 +0000
@@ -0,0 +1,1 @@
+http://os.mbed.com/users/mbed_official/code/mbed-rtos/#5713cbbdb706
diff -r 000000000000 -r d98bd8b7dc46 mbed.bld
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Mon Apr 09 15:57:36 2018 +0000
@@ -0,0 +1,1 @@
+https://os.mbed.com/users/mbed_official/code/mbed/builds/994bdf8177cb
\ No newline at end of file