MPU9250.h

00001 #ifndef MPU9250_H
00002 #define MPU9250_H
00003  
00004 #include "mbed.h"
00005 #include "math.h"
00006  
00007 // 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 
00008 // above document; the MPU9250 and MPU9150 are virtually identical but the latter has a different register map
00009 //
00010 //Magnetometer Registers
00011 #define AK8963_ADDRESS   0x0C<<1
00012 #define WHO_AM_I_AK8963  0x00 // should return 0x48
00013 #define INFO             0x01
00014 #define AK8963_ST1       0x02  // data ready status bit 0
00015 #define AK8963_XOUT_L    0x03  // data
00016 #define AK8963_XOUT_H    0x04
00017 #define AK8963_YOUT_L    0x05
00018 #define AK8963_YOUT_H    0x06
00019 #define AK8963_ZOUT_L    0x07
00020 #define AK8963_ZOUT_H    0x08
00021 #define AK8963_ST2       0x09  // Data overflow bit 3 and data read error status bit 2
00022 #define AK8963_CNTL      0x0A  // Power down (0000), single-measurement (0001), self-test (1000) and Fuse ROM (1111) modes on bits 3:0
00023 #define AK8963_ASTC      0x0C  // Self test control
00024 #define AK8963_I2CDIS    0x0F  // I2C disable
00025 #define AK8963_ASAX      0x10  // Fuse ROM x-axis sensitivity adjustment value
00026 #define AK8963_ASAY      0x11  // Fuse ROM y-axis sensitivity adjustment value
00027 #define AK8963_ASAZ      0x12  // Fuse ROM z-axis sensitivity adjustment value
00028 
00029 #define SELF_TEST_X_GYRO 0x00                  
00030 #define SELF_TEST_Y_GYRO 0x01                                                                          
00031 #define SELF_TEST_Z_GYRO 0x02
00032 
00033 /*#define X_FINE_GAIN      0x03 // [7:0] fine gain
00034 #define Y_FINE_GAIN      0x04
00035 #define Z_FINE_GAIN      0x05
00036 #define XA_OFFSET_H      0x06 // User-defined trim values for accelerometer
00037 #define XA_OFFSET_L_TC   0x07
00038 #define YA_OFFSET_H      0x08
00039 #define YA_OFFSET_L_TC   0x09
00040 #define ZA_OFFSET_H      0x0A
00041 #define ZA_OFFSET_L_TC   0x0B */
00042 
00043 #define SELF_TEST_X_ACCEL 0x0D
00044 #define SELF_TEST_Y_ACCEL 0x0E    
00045 #define SELF_TEST_Z_ACCEL 0x0F
00046 
00047 #define SELF_TEST_A      0x10
00048 
00049 #define XG_OFFSET_H      0x13  // User-defined trim values for gyroscope
00050 #define XG_OFFSET_L      0x14
00051 #define YG_OFFSET_H      0x15
00052 #define YG_OFFSET_L      0x16
00053 #define ZG_OFFSET_H      0x17
00054 #define ZG_OFFSET_L      0x18
00055 #define SMPLRT_DIV       0x19
00056 #define CONFIG           0x1A
00057 #define GYRO_CONFIG      0x1B
00058 #define ACCEL_CONFIG     0x1C
00059 #define ACCEL_CONFIG2    0x1D
00060 #define LP_ACCEL_ODR     0x1E   
00061 #define WOM_THR          0x1F   
00062 
00063 #define MOT_DUR          0x20  // Duration counter threshold for motion interrupt generation, 1 kHz rate, LSB = 1 ms
00064 #define ZMOT_THR         0x21  // Zero-motion detection threshold bits [7:0]
00065 #define ZRMOT_DUR        0x22  // Duration counter threshold for zero motion interrupt generation, 16 Hz rate, LSB = 64 ms
00066 
00067 #define FIFO_EN          0x23
00068 #define I2C_MST_CTRL     0x24   
00069 #define I2C_SLV0_ADDR    0x25
00070 #define I2C_SLV0_REG     0x26
00071 #define I2C_SLV0_CTRL    0x27
00072 #define I2C_SLV1_ADDR    0x28
00073 #define I2C_SLV1_REG     0x29
00074 #define I2C_SLV1_CTRL    0x2A
00075 #define I2C_SLV2_ADDR    0x2B
00076 #define I2C_SLV2_REG     0x2C
00077 #define I2C_SLV2_CTRL    0x2D
00078 #define I2C_SLV3_ADDR    0x2E
00079 #define I2C_SLV3_REG     0x2F
00080 #define I2C_SLV3_CTRL    0x30
00081 #define I2C_SLV4_ADDR    0x31
00082 #define I2C_SLV4_REG     0x32
00083 #define I2C_SLV4_DO      0x33
00084 #define I2C_SLV4_CTRL    0x34
00085 #define I2C_SLV4_DI      0x35
00086 #define I2C_MST_STATUS   0x36
00087 #define INT_PIN_CFG      0x37
00088 #define INT_ENABLE       0x38
00089 #define DMP_INT_STATUS   0x39  // Check DMP interrupt
00090 #define INT_STATUS       0x3A
00091 #define ACCEL_XOUT_H     0x3B
00092 #define ACCEL_XOUT_L     0x3C
00093 #define ACCEL_YOUT_H     0x3D
00094 #define ACCEL_YOUT_L     0x3E
00095 #define ACCEL_ZOUT_H     0x3F
00096 #define ACCEL_ZOUT_L     0x40
00097 #define TEMP_OUT_H       0x41
00098 #define TEMP_OUT_L       0x42
00099 #define GYRO_XOUT_H      0x43
00100 #define GYRO_XOUT_L      0x44
00101 #define GYRO_YOUT_H      0x45
00102 #define GYRO_YOUT_L      0x46
00103 #define GYRO_ZOUT_H      0x47
00104 #define GYRO_ZOUT_L      0x48
00105 #define EXT_SENS_DATA_00 0x49
00106 #define EXT_SENS_DATA_01 0x4A
00107 #define EXT_SENS_DATA_02 0x4B
00108 #define EXT_SENS_DATA_03 0x4C
00109 #define EXT_SENS_DATA_04 0x4D
00110 #define EXT_SENS_DATA_05 0x4E
00111 #define EXT_SENS_DATA_06 0x4F
00112 #define EXT_SENS_DATA_07 0x50
00113 #define EXT_SENS_DATA_08 0x51
00114 #define EXT_SENS_DATA_09 0x52
00115 #define EXT_SENS_DATA_10 0x53
00116 #define EXT_SENS_DATA_11 0x54
00117 #define EXT_SENS_DATA_12 0x55
00118 #define EXT_SENS_DATA_13 0x56
00119 #define EXT_SENS_DATA_14 0x57
00120 #define EXT_SENS_DATA_15 0x58
00121 #define EXT_SENS_DATA_16 0x59
00122 #define EXT_SENS_DATA_17 0x5A
00123 #define EXT_SENS_DATA_18 0x5B
00124 #define EXT_SENS_DATA_19 0x5C
00125 #define EXT_SENS_DATA_20 0x5D
00126 #define EXT_SENS_DATA_21 0x5E
00127 #define EXT_SENS_DATA_22 0x5F
00128 #define EXT_SENS_DATA_23 0x60
00129 #define MOT_DETECT_STATUS 0x61
00130 #define I2C_SLV0_DO      0x63
00131 #define I2C_SLV1_DO      0x64
00132 #define I2C_SLV2_DO      0x65
00133 #define I2C_SLV3_DO      0x66
00134 #define I2C_MST_DELAY_CTRL 0x67
00135 #define SIGNAL_PATH_RESET  0x68
00136 #define MOT_DETECT_CTRL  0x69
00137 #define USER_CTRL        0x6A  // Bit 7 enable DMP, bit 3 reset DMP
00138 #define PWR_MGMT_1       0x6B // Device defaults to the SLEEP mode
00139 #define PWR_MGMT_2       0x6C
00140 #define DMP_BANK         0x6D  // Activates a specific bank in the DMP
00141 #define DMP_RW_PNT       0x6E  // Set read/write pointer to a specific start address in specified DMP bank
00142 #define DMP_REG          0x6F  // Register in DMP from which to read or to which to write
00143 #define DMP_REG_1        0x70
00144 #define DMP_REG_2        0x71 
00145 #define FIFO_COUNTH      0x72
00146 #define FIFO_COUNTL      0x73
00147 #define FIFO_R_W         0x74
00148 #define WHO_AM_I_MPU9250 0x75 // Should return 0x71
00149 #define XA_OFFSET_H      0x77
00150 #define XA_OFFSET_L      0x78
00151 #define YA_OFFSET_H      0x7A
00152 #define YA_OFFSET_L      0x7B
00153 #define ZA_OFFSET_H      0x7D
00154 #define ZA_OFFSET_L      0x7E
00155 
00156 // Using the MSENSR-9250 breakout board, ADO is set to 0 
00157 // Seven-bit device address is 110100 for ADO = 0 and 110101 for ADO = 1
00158 //mbed uses the eight-bit device address, so shift seven-bit addresses left by one!
00159 #define ADO 0
00160 #if ADO
00161 #define MPU9250_ADDRESS 0x69<<1  // Device address when ADO = 1
00162 #else
00163 #define MPU9250_ADDRESS 0x68<<1  // Device address when ADO = 0
00164 #endif  
00165 
00166 // Set initial input parameters
00167 enum Ascale {
00168   AFS_2G = 0,
00169   AFS_4G,
00170   AFS_8G,
00171   AFS_16G
00172 };
00173 
00174 enum Gscale {
00175   GFS_250DPS = 0,
00176   GFS_500DPS,
00177   GFS_1000DPS,
00178   GFS_2000DPS
00179 };
00180 
00181 enum Mscale {
00182   MFS_14BITS = 0, // 0.6 mG per LSB
00183   MFS_16BITS      // 0.15 mG per LSB
00184 };
00185 
00186 uint8_t Ascale = AFS_2G;     // AFS_2G, AFS_4G, AFS_8G, AFS_16G
00187 uint8_t Gscale = GFS_250DPS; // GFS_250DPS, GFS_500DPS, GFS_1000DPS, GFS_2000DPS
00188 uint8_t Mscale = MFS_16BITS; // MFS_14BITS or MFS_16BITS, 14-bit or 16-bit magnetometer resolution
00189 uint8_t Mmode = 0x06;        // Either 8 Hz 0x02) or 100 Hz (0x06) magnetometer data ODR  
00190 float aRes, gRes, mRes;      // scale resolutions per LSB for the sensors
00191 
00192 //Set up I2C, (SDA,SCL)
00193 //I2C i2c(I2C_SDA, I2C_SCL);
00194 I2C i2c(PC_9, PA_8);
00195 
00196 DigitalOut myled(LED1);
00197     
00198 // Pin definitions
00199 int intPin = 12;  // These can be changed, 2 and 3 are the Arduinos ext int pins
00200 
00201 int16_t accelCount[3];  // Stores the 16-bit signed accelerometer sensor output
00202 int16_t gyroCount[3];   // Stores the 16-bit signed gyro sensor output
00203 int16_t magCount[3];    // Stores the 16-bit signed magnetometer sensor output
00204 float magCalibration[3] = {0, 0, 0}, magbias[3] = {0, 0, 0};  // Factory mag calibration and mag bias
00205 float gyroBias[3] = {0, 0, 0}, accelBias[3] = {0, 0, 0}; // Bias corrections for gyro and accelerometer
00206 float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values 
00207 int16_t tempCount;   // Stores the real internal chip temperature in degrees Celsius
00208 float temperature;
00209 float SelfTest[6];
00210 
00211 int delt_t = 0; // used to control display output rate
00212 int count = 0;  // used to control display output rate
00213 
00214 // parameters for 6 DoF sensor fusion calculations
00215 float PI = 3.14159265358979323846f;
00216 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
00217 float beta = sqrt(3.0f / 4.0f) * GyroMeasError;  // compute beta
00218 float GyroMeasDrift = PI * (1.0f / 180.0f);      // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s)
00219 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
00220 #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
00221 #define Ki 0.0f
00222 
00223 float pitch, yaw, roll;
00224 float deltat = 0.0f;                             // integration interval for both filter schemes
00225 int lastUpdate = 0, firstUpdate = 0, Now = 0;    // used to calculate integration interval                               // used to calculate integration interval
00226 float q[4] = {1.0f, 0.0f, 0.0f, 0.0f};           // vector to hold quaternion
00227 float eInt[3] = {0.0f, 0.0f, 0.0f};              // vector to hold integral error for Mahony method
00228 
00229 class MPU9250 {
00230  
00231     protected:
00232  
00233     public:
00234   //===================================================================================================================
00235 //====== Set of useful function to access acceleratio, gyroscope, and temperature data
00236 //===================================================================================================================
00237 
00238     void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
00239 {
00240    char data_write[2];
00241    data_write[0] = subAddress;
00242    data_write[1] = data;
00243    i2c.write(address, data_write, 2, 0);
00244 }
00245 
00246     char readByte(uint8_t address, uint8_t subAddress)
00247 {
00248     char data[1]; // `data` will store the register data     
00249     char data_write[1];
00250     data_write[0] = subAddress;
00251     i2c.write(address, data_write, 1, 1); // no stop
00252     i2c.read(address, data, 1, 0); 
00253     return data[0]; 
00254 }
00255 
00256     void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
00257 {     
00258     char data[14];
00259     char data_write[1];
00260     data_write[0] = subAddress;
00261     i2c.write(address, data_write, 1, 1); // no stop
00262     i2c.read(address, data, count, 0); 
00263     for(int ii = 0; ii < count; ii++) {
00264      dest[ii] = data[ii];
00265     }
00266 } 
00267  
00268 
00269 void getMres() {
00270   switch (Mscale)
00271   {
00272     // Possible magnetometer scales (and their register bit settings) are:
00273     // 14 bit resolution (0) and 16 bit resolution (1)
00274     case MFS_14BITS:
00275           mRes = 10.0*4219.0/8190.0; // Proper scale to return milliGauss
00276           break;
00277     case MFS_16BITS:
00278           mRes = 10.0*4219.0/32760.0; // Proper scale to return milliGauss
00279           break;
00280   }
00281 }
00282 
00283 
00284 void getGres() {
00285   switch (Gscale)
00286   {
00287     // Possible gyro scales (and their register bit settings) are:
00288     // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS  (11). 
00289         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00290     case GFS_250DPS:
00291           gRes = 250.0/32768.0;
00292           break;
00293     case GFS_500DPS:
00294           gRes = 500.0/32768.0;
00295           break;
00296     case GFS_1000DPS:
00297           gRes = 1000.0/32768.0;
00298           break;
00299     case GFS_2000DPS:
00300           gRes = 2000.0/32768.0;
00301           break;
00302   }
00303 }
00304 
00305 
00306 void getAres() {
00307   switch (Ascale)
00308   {
00309     // Possible accelerometer scales (and their register bit settings) are:
00310     // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs  (11). 
00311         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00312     case AFS_2G:
00313           aRes = 2.0/32768.0;
00314           break;
00315     case AFS_4G:
00316           aRes = 4.0/32768.0;
00317           break;
00318     case AFS_8G:
00319           aRes = 8.0/32768.0;
00320           break;
00321     case AFS_16G:
00322           aRes = 16.0/32768.0;
00323           break;
00324   }
00325 }
00326 
00327 
00328 void readAccelData(int16_t * destination)
00329 {
00330   uint8_t rawData[6];  // x/y/z accel register data stored here
00331   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
00332   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00333   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
00334   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
00335 }
00336 
00337 void readGyroData(int16_t * destination)
00338 {
00339   uint8_t rawData[6];  // x/y/z gyro register data stored here
00340   readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
00341   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00342   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
00343   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
00344 }
00345 
00346 void readMagData(int16_t * destination)
00347 {
00348   uint8_t rawData[7];  // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition
00349   if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set
00350   readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]);  // Read the six raw data and ST2 registers sequentially into data array
00351   uint8_t c = rawData[6]; // End data read by reading ST2 register
00352     if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data
00353     destination[0] = (int16_t)(((int16_t)rawData[1] << 8) | rawData[0]);  // Turn the MSB and LSB into a signed 16-bit value
00354     destination[1] = (int16_t)(((int16_t)rawData[3] << 8) | rawData[2]) ;  // Data stored as little Endian
00355     destination[2] = (int16_t)(((int16_t)rawData[5] << 8) | rawData[4]) ; 
00356    }
00357   }
00358 }
00359 
00360 int16_t readTempData()
00361 {
00362   uint8_t rawData[2];  // x/y/z gyro register data stored here
00363   readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]);  // Read the two raw data registers sequentially into data array 
00364   return (int16_t)(((int16_t)rawData[0]) << 8 | rawData[1]) ;  // Turn the MSB and LSB into a 16-bit value
00365 }
00366 
00367 
00368 void resetMPU9250() {
00369   // reset device
00370   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00371   wait(0.1);
00372   }
00373   
00374   void initAK8963(float * destination)
00375 {
00376   // First extract the factory calibration for each magnetometer axis
00377   uint8_t rawData[3];  // x/y/z gyro calibration data stored here
00378   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
00379   wait(0.01);
00380   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode
00381   wait(0.01);
00382   readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
00383   destination[0] =  (float)(rawData[0] - 128)/256.0f + 1.0f;   // Return x-axis sensitivity adjustment values, etc.
00384   destination[1] =  (float)(rawData[1] - 128)/256.0f + 1.0f;  
00385   destination[2] =  (float)(rawData[2] - 128)/256.0f + 1.0f; 
00386   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
00387   wait(0.01);
00388   // Configure the magnetometer for continuous read and highest resolution
00389   // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register,
00390   // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates
00391   writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR
00392   wait(0.01);
00393 }
00394 
00395 
00396 void initMPU9250()
00397 {  
00398  // Initialize MPU9250 device
00399  // wake up device
00400   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors 
00401   wait(0.1); // Delay 100 ms for PLL to get established on x-axis gyro; should check for PLL ready interrupt  
00402 
00403  // get stable time source
00404   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00405 
00406  // Configure Gyro and Accelerometer
00407  // Disable FSYNC and set accelerometer and gyro bandwidth to 44 and 42 Hz, respectively; 
00408  // DLPF_CFG = bits 2:0 = 010; this sets the sample rate at 1 kHz for both
00409  // Maximum delay is 4.9 ms which is just over a 200 Hz maximum rate
00410   writeByte(MPU9250_ADDRESS, CONFIG, 0x03);  
00411  
00412  // Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV)
00413   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04);  // Use a 200 Hz rate; the same rate set in CONFIG above
00414  
00415  // Set gyroscope full scale range
00416  // Range selects FS_SEL and AFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
00417   uint8_t c = readByte(MPU9250_ADDRESS, GYRO_CONFIG); // get current GYRO_CONFIG register value
00418  // c = c & ~0xE0; // Clear self-test bits [7:5] 
00419   c = c & ~0x02; // Clear Fchoice bits [1:0] 
00420   c = c & ~0x18; // Clear AFS bits [4:3]
00421   c = c | Gscale << 3; // Set full scale range for the gyro
00422  // c =| 0x00; // Set Fchoice for the gyro to 11 by writing its inverse to bits 1:0 of GYRO_CONFIG
00423   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c ); // Write new GYRO_CONFIG value to register
00424   
00425  // Set accelerometer full-scale range configuration
00426   c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG); // get current ACCEL_CONFIG register value
00427  // c = c & ~0xE0; // Clear self-test bits [7:5] 
00428   c = c & ~0x18;  // Clear AFS bits [4:3]
00429   c = c | Ascale << 3; // Set full scale range for the accelerometer 
00430   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c); // Write new ACCEL_CONFIG register value
00431 
00432  // Set accelerometer sample rate configuration
00433  // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for
00434  // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz
00435   c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2); // get current ACCEL_CONFIG2 register value
00436   c = c & ~0x0F; // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])  
00437   c = c | 0x03;  // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
00438   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c); // Write new ACCEL_CONFIG2 register value
00439 
00440  // The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, 
00441  // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting
00442 
00443   // Configure Interrupts and Bypass Enable
00444   // Set interrupt pin active high, push-pull, and clear on read of INT_STATUS, enable I2C_BYPASS_EN so additional chips 
00445   // can join the I2C bus and all can be controlled by the Arduino as master
00446    writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22);    
00447    writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
00448 }
00449 
00450 // Function which accumulates gyro and accelerometer data after device initialization. It calculates the average
00451 // of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers.
00452 void calibrateMPU9250(float * dest1, float * dest2)
00453 {  
00454   uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data
00455   uint16_t ii, packet_count, fifo_count;
00456   int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};
00457   
00458 // reset device, reset all registers, clear gyro and accelerometer bias registers
00459   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00460   wait(0.1);  
00461    
00462 // get stable time source
00463 // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00464   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  
00465   writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00); 
00466   wait(0.2);
00467   
00468 // Configure device for bias calculation
00469   writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00);   // Disable all interrupts
00470   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);      // Disable FIFO
00471   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00);   // Turn on internal clock source
00472   writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master
00473   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00);    // Disable FIFO and I2C master modes
00474   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C);    // Reset FIFO and DMP
00475   wait(0.015);
00476   
00477 // Configure MPU9250 gyro and accelerometer for bias calculation
00478   writeByte(MPU9250_ADDRESS, CONFIG, 0x01);      // Set low-pass filter to 188 Hz
00479   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00);  // Set sample rate to 1 kHz
00480   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);  // Set gyro full-scale to 250 degrees per second, maximum sensitivity
00481   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity
00482  
00483   uint16_t  gyrosensitivity  = 131;   // = 131 LSB/degrees/sec
00484   uint16_t  accelsensitivity = 16384;  // = 16384 LSB/g
00485 
00486 // Configure FIFO to capture accelerometer and gyro data for bias calculation
00487   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40);   // Enable FIFO  
00488   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78);     // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9250)
00489   wait(0.04); // accumulate 40 samples in 80 milliseconds = 480 bytes
00490 
00491 // At end of sample accumulation, turn off FIFO sensor read
00492   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);        // Disable gyro and accelerometer sensors for FIFO
00493   readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count
00494   fifo_count = ((uint16_t)data[0] << 8) | data[1];
00495   packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging
00496 
00497   for (ii = 0; ii < packet_count; ii++) {
00498     int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0};
00499     readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging
00500     accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1]  ) ;  // Form signed 16-bit integer for each sample in FIFO
00501     accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3]  ) ;
00502     accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5]  ) ;    
00503     gyro_temp[0]  = (int16_t) (((int16_t)data[6] << 8) | data[7]  ) ;
00504     gyro_temp[1]  = (int16_t) (((int16_t)data[8] << 8) | data[9]  ) ;
00505     gyro_temp[2]  = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;
00506     
00507     accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
00508     accel_bias[1] += (int32_t) accel_temp[1];
00509     accel_bias[2] += (int32_t) accel_temp[2];
00510     gyro_bias[0]  += (int32_t) gyro_temp[0];
00511     gyro_bias[1]  += (int32_t) gyro_temp[1];
00512     gyro_bias[2]  += (int32_t) gyro_temp[2];
00513             
00514 }
00515     accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases
00516     accel_bias[1] /= (int32_t) packet_count;
00517     accel_bias[2] /= (int32_t) packet_count;
00518     gyro_bias[0]  /= (int32_t) packet_count;
00519     gyro_bias[1]  /= (int32_t) packet_count;
00520     gyro_bias[2]  /= (int32_t) packet_count;
00521     
00522   if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;}  // Remove gravity from the z-axis accelerometer bias calculation
00523   else {accel_bias[2] += (int32_t) accelsensitivity;}
00524  
00525 // Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup
00526   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
00527   data[1] = (-gyro_bias[0]/4)       & 0xFF; // Biases are additive, so change sign on calculated average gyro biases
00528   data[2] = (-gyro_bias[1]/4  >> 8) & 0xFF;
00529   data[3] = (-gyro_bias[1]/4)       & 0xFF;
00530   data[4] = (-gyro_bias[2]/4  >> 8) & 0xFF;
00531   data[5] = (-gyro_bias[2]/4)       & 0xFF;
00532 
00533 /// Push gyro biases to hardware registers
00534 /*  writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]);
00535   writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]);
00536   writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]);
00537   writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]);
00538   writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]);
00539   writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);
00540 */
00541   dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; // construct gyro bias in deg/s for later manual subtraction
00542   dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity;
00543   dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;
00544 
00545 // Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain
00546 // factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold
00547 // non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature
00548 // compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that
00549 // the accelerometer biases calculated above must be divided by 8.
00550 
00551   int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases
00552   readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values
00553   accel_bias_reg[0] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00554   readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]);
00555   accel_bias_reg[1] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00556   readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
00557   accel_bias_reg[2] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00558   
00559   uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers
00560   uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis
00561   
00562   for(ii = 0; ii < 3; ii++) {
00563     if(accel_bias_reg[ii] & mask) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit
00564   }
00565 
00566   // Construct total accelerometer bias, including calculated average accelerometer bias from above
00567   accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale)
00568   accel_bias_reg[1] -= (accel_bias[1]/8);
00569   accel_bias_reg[2] -= (accel_bias[2]/8);
00570  
00571   data[0] = (accel_bias_reg[0] >> 8) & 0xFF;
00572   data[1] = (accel_bias_reg[0])      & 0xFF;
00573   data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00574   data[2] = (accel_bias_reg[1] >> 8) & 0xFF;
00575   data[3] = (accel_bias_reg[1])      & 0xFF;
00576   data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00577   data[4] = (accel_bias_reg[2] >> 8) & 0xFF;
00578   data[5] = (accel_bias_reg[2])      & 0xFF;
00579   data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00580 
00581 // Apparently this is not working for the acceleration biases in the MPU-9250
00582 // Are we handling the temperature correction bit properly?
00583 // Push accelerometer biases to hardware registers
00584 /*  writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]);
00585   writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]);
00586   writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]);
00587   writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]);
00588   writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]);
00589   writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);
00590 */
00591 // Output scaled accelerometer biases for manual subtraction in the main program
00592    dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; 
00593    dest2[1] = (float)accel_bias[1]/(float)accelsensitivity;
00594    dest2[2] = (float)accel_bias[2]/(float)accelsensitivity;
00595 }
00596 
00597 
00598 // Accelerometer and gyroscope self test; check calibration wrt factory settings
00599 void MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass
00600 {
00601    uint8_t rawData[6] = {0, 0, 0, 0, 0, 0};
00602    uint8_t selfTest[6];
00603    int16_t gAvg[3], aAvg[3], aSTAvg[3], gSTAvg[3];
00604    float factoryTrim[6];
00605    uint8_t FS = 0;
00606    
00607   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz
00608   writeByte(MPU9250_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz
00609   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 1<<FS); // Set full scale range for the gyro to 250 dps
00610   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz
00611   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 1<<FS); // Set full scale range for the accelerometer to 2 g
00612 
00613   for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer
00614   
00615   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00616   aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00617   aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00618   aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00619   
00620     readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00621   gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00622   gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00623   gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00624   }
00625   
00626   for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average current readings
00627   aAvg[ii] /= 200;
00628   gAvg[ii] /= 200;
00629   }
00630   
00631 // Configure the accelerometer for self-test
00632    writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g
00633    writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s
00634    //delay(55); // Delay a while to let the device stabilize
00635 
00636   for( int ii = 0; ii < 200; ii++) { // get average self-test values of gyro and acclerometer
00637   
00638   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00639   aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00640   aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00641   aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00642   
00643     readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00644   gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00645   gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00646   gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00647   }
00648   
00649   for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average self-test readings
00650   aSTAvg[ii] /= 200;
00651   gSTAvg[ii] /= 200;
00652   }
00653   
00654  // Configure the gyro and accelerometer for normal operation
00655    writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00);
00656    writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);
00657    //delay(45); // Delay a while to let the device stabilize
00658    
00659    // Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg
00660    selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results
00661    selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results
00662    selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results
00663    selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results
00664    selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results
00665    selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results
00666 
00667   // Retrieve factory self-test value from self-test code reads
00668    factoryTrim[0] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation
00669    factoryTrim[1] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation
00670    factoryTrim[2] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation
00671    factoryTrim[3] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation
00672    factoryTrim[4] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation
00673    factoryTrim[5] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation
00674  
00675  // Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response
00676  // To get percent, must multiply by 100
00677    for (int i = 0; i < 3; i++) {
00678      destination[i] = 100.0*((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i]; // Report percent differences
00679      destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3]; // Report percent differences
00680    }
00681    
00682 }
00683 
00684 
00685 
00686 // Implementation of Sebastian Madgwick's "...efficient orientation filter for... inertial/magnetic sensor arrays"
00687 // (see http://www.x-io.co.uk/category/open-source/ for examples and more details)
00688 // which fuses acceleration, rotation rate, and magnetic moments to produce a quaternion-based estimate of absolute
00689 // device orientation -- which can be converted to yaw, pitch, and roll. Useful for stabilizing quadcopters, etc.
00690 // The performance of the orientation filter is at least as good as conventional Kalman-based filtering algorithms
00691 // but is much less computationally intensive---it can be performed on a 3.3 V Pro Mini operating at 8 MHz!
00692         void MadgwickQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
00693         {
00694             float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
00695             float norm;
00696             float hx, hy, _2bx, _2bz;
00697             float s1, s2, s3, s4;
00698             float qDot1, qDot2, qDot3, qDot4;
00699 
00700             // Auxiliary variables to avoid repeated arithmetic
00701             float _2q1mx;
00702             float _2q1my;
00703             float _2q1mz;
00704             float _2q2mx;
00705             float _4bx;
00706             float _4bz;
00707             float _2q1 = 2.0f * q1;
00708             float _2q2 = 2.0f * q2;
00709             float _2q3 = 2.0f * q3;
00710             float _2q4 = 2.0f * q4;
00711             float _2q1q3 = 2.0f * q1 * q3;
00712             float _2q3q4 = 2.0f * q3 * q4;
00713             float q1q1 = q1 * q1;
00714             float q1q2 = q1 * q2;
00715             float q1q3 = q1 * q3;
00716             float q1q4 = q1 * q4;
00717             float q2q2 = q2 * q2;
00718             float q2q3 = q2 * q3;
00719             float q2q4 = q2 * q4;
00720             float q3q3 = q3 * q3;
00721             float q3q4 = q3 * q4;
00722             float q4q4 = q4 * q4;
00723 
00724             // Normalise accelerometer measurement
00725             norm = sqrt(ax * ax + ay * ay + az * az);
00726             if (norm == 0.0f) return; // handle NaN
00727             norm = 1.0f/norm;
00728             ax *= norm;
00729             ay *= norm;
00730             az *= norm;
00731 
00732             // Normalise magnetometer measurement
00733             norm = sqrt(mx * mx + my * my + mz * mz);
00734             if (norm == 0.0f) return; // handle NaN
00735             norm = 1.0f/norm;
00736             mx *= norm;
00737             my *= norm;
00738             mz *= norm;
00739 
00740             // Reference direction of Earth's magnetic field
00741             _2q1mx = 2.0f * q1 * mx;
00742             _2q1my = 2.0f * q1 * my;
00743             _2q1mz = 2.0f * q1 * mz;
00744             _2q2mx = 2.0f * q2 * mx;
00745             hx = mx * q1q1 - _2q1my * q4 + _2q1mz * q3 + mx * q2q2 + _2q2 * my * q3 + _2q2 * mz * q4 - mx * q3q3 - mx * q4q4;
00746             hy = _2q1mx * q4 + my * q1q1 - _2q1mz * q2 + _2q2mx * q3 - my * q2q2 + my * q3q3 + _2q3 * mz * q4 - my * q4q4;
00747             _2bx = sqrt(hx * hx + hy * hy);
00748             _2bz = -_2q1mx * q3 + _2q1my * q2 + mz * q1q1 + _2q2mx * q4 - mz * q2q2 + _2q3 * my * q4 - mz * q3q3 + mz * q4q4;
00749             _4bx = 2.0f * _2bx;
00750             _4bz = 2.0f * _2bz;
00751 
00752             // Gradient decent algorithm corrective step
00753             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);
00754             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);
00755             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);
00756             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);
00757             norm = sqrt(s1 * s1 + s2 * s2 + s3 * s3 + s4 * s4);    // normalise step magnitude
00758             norm = 1.0f/norm;
00759             s1 *= norm;
00760             s2 *= norm;
00761             s3 *= norm;
00762             s4 *= norm;
00763 
00764             // Compute rate of change of quaternion
00765             qDot1 = 0.5f * (-q2 * gx - q3 * gy - q4 * gz) - beta * s1;
00766             qDot2 = 0.5f * (q1 * gx + q3 * gz - q4 * gy) - beta * s2;
00767             qDot3 = 0.5f * (q1 * gy - q2 * gz + q4 * gx) - beta * s3;
00768             qDot4 = 0.5f * (q1 * gz + q2 * gy - q3 * gx) - beta * s4;
00769 
00770             // Integrate to yield quaternion
00771             q1 += qDot1 * deltat;
00772             q2 += qDot2 * deltat;
00773             q3 += qDot3 * deltat;
00774             q4 += qDot4 * deltat;
00775             norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);    // normalise quaternion
00776             norm = 1.0f/norm;
00777             q[0] = q1 * norm;
00778             q[1] = q2 * norm;
00779             q[2] = q3 * norm;
00780             q[3] = q4 * norm;
00781 
00782         }
00783   
00784   
00785   
00786  // Similar to Madgwick scheme but uses proportional and integral filtering on the error between estimated reference vectors and
00787  // measured ones. 
00788             void MahonyQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
00789         {
00790             float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
00791             float norm;
00792             float hx, hy, bx, bz;
00793             float vx, vy, vz, wx, wy, wz;
00794             float ex, ey, ez;
00795             float pa, pb, pc;
00796 
00797             // Auxiliary variables to avoid repeated arithmetic
00798             float q1q1 = q1 * q1;
00799             float q1q2 = q1 * q2;
00800             float q1q3 = q1 * q3;
00801             float q1q4 = q1 * q4;
00802             float q2q2 = q2 * q2;
00803             float q2q3 = q2 * q3;
00804             float q2q4 = q2 * q4;
00805             float q3q3 = q3 * q3;
00806             float q3q4 = q3 * q4;
00807             float q4q4 = q4 * q4;   
00808 
00809             // Normalise accelerometer measurement
00810             norm = sqrt(ax * ax + ay * ay + az * az);
00811             if (norm == 0.0f) return; // handle NaN
00812             norm = 1.0f / norm;        // use reciprocal for division
00813             ax *= norm;
00814             ay *= norm;
00815             az *= norm;
00816 
00817             // Normalise magnetometer measurement
00818             norm = sqrt(mx * mx + my * my + mz * mz);
00819             if (norm == 0.0f) return; // handle NaN
00820             norm = 1.0f / norm;        // use reciprocal for division
00821             mx *= norm;
00822             my *= norm;
00823             mz *= norm;
00824 
00825             // Reference direction of Earth's magnetic field
00826             hx = 2.0f * mx * (0.5f - q3q3 - q4q4) + 2.0f * my * (q2q3 - q1q4) + 2.0f * mz * (q2q4 + q1q3);
00827             hy = 2.0f * mx * (q2q3 + q1q4) + 2.0f * my * (0.5f - q2q2 - q4q4) + 2.0f * mz * (q3q4 - q1q2);
00828             bx = sqrt((hx * hx) + (hy * hy));
00829             bz = 2.0f * mx * (q2q4 - q1q3) + 2.0f * my * (q3q4 + q1q2) + 2.0f * mz * (0.5f - q2q2 - q3q3);
00830 
00831             // Estimated direction of gravity and magnetic field
00832             vx = 2.0f * (q2q4 - q1q3);
00833             vy = 2.0f * (q1q2 + q3q4);
00834             vz = q1q1 - q2q2 - q3q3 + q4q4;
00835             wx = 2.0f * bx * (0.5f - q3q3 - q4q4) + 2.0f * bz * (q2q4 - q1q3);
00836             wy = 2.0f * bx * (q2q3 - q1q4) + 2.0f * bz * (q1q2 + q3q4);
00837             wz = 2.0f * bx * (q1q3 + q2q4) + 2.0f * bz * (0.5f - q2q2 - q3q3);  
00838 
00839             // Error is cross product between estimated direction and measured direction of gravity
00840             ex = (ay * vz - az * vy) + (my * wz - mz * wy);
00841             ey = (az * vx - ax * vz) + (mz * wx - mx * wz);
00842             ez = (ax * vy - ay * vx) + (mx * wy - my * wx);
00843             if (Ki > 0.0f)
00844             {
00845                 eInt[0] += ex;      // accumulate integral error
00846                 eInt[1] += ey;
00847                 eInt[2] += ez;
00848             }
00849             else
00850             {
00851                 eInt[0] = 0.0f;     // prevent integral wind up
00852                 eInt[1] = 0.0f;
00853                 eInt[2] = 0.0f;
00854             }
00855 
00856             // Apply feedback terms
00857             gx = gx + Kp * ex + Ki * eInt[0];
00858             gy = gy + Kp * ey + Ki * eInt[1];
00859             gz = gz + Kp * ez + Ki * eInt[2];
00860 
00861             // Integrate rate of change of quaternion
00862             pa = q2;
00863             pb = q3;
00864             pc = q4;
00865             q1 = q1 + (-q2 * gx - q3 * gy - q4 * gz) * (0.5f * deltat);
00866             q2 = pa + (q1 * gx + pb * gz - pc * gy) * (0.5f * deltat);
00867             q3 = pb + (q1 * gy - pa * gz + pc * gx) * (0.5f * deltat);
00868             q4 = pc + (q1 * gz + pa * gy - pb * gx) * (0.5f * deltat);
00869 
00870             // Normalise quaternion
00871             norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);
00872             norm = 1.0f / norm;
00873             q[0] = q1 * norm;
00874             q[1] = q2 * norm;
00875             q[2] = q3 * norm;
00876             q[3] = q4 * norm;
00877  
00878         }
00879   };
00880 #endif