Comparison with attitude estimation filter IMU : MPU9250

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MPU9250.h

00001 //------------------------------------------------------------------------------
00002 // Attitude measurement using IMU(MPU-9250)
00003 //------------------------------------------------------------------------------
00004 #ifndef MPU9250_H
00005 #define MPU9250_H
00006 
00007 #include "mbed.h"
00008 #include "math.h"
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 /*
00034 #define X_FINE_GAIN      0x03 // [7:0] fine gain
00035 #define Y_FINE_GAIN      0x04
00036 #define Z_FINE_GAIN      0x05
00037 #define XA_OFFSET_H      0x06 // User-defined trim values for accelerometer
00038 #define XA_OFFSET_L_TC   0x07
00039 #define YA_OFFSET_H      0x08
00040 #define YA_OFFSET_L_TC   0x09
00041 #define ZA_OFFSET_H      0x0A
00042 #define ZA_OFFSET_L_TC   0x0B
00043 */
00044 
00045 #define SELF_TEST_X_ACCEL 0x0D
00046 #define SELF_TEST_Y_ACCEL 0x0E
00047 #define SELF_TEST_Z_ACCEL 0x0F
00048 
00049 #define SELF_TEST_A      0x10
00050 
00051 #define XG_OFFSET_H      0x13  // User-defined trim values for gyroscope
00052 #define XG_OFFSET_L      0x14
00053 #define YG_OFFSET_H      0x15
00054 #define YG_OFFSET_L      0x16
00055 #define ZG_OFFSET_H      0x17
00056 #define ZG_OFFSET_L      0x18
00057 #define SMPLRT_DIV       0x19
00058 #define CONFIG           0x1A
00059 #define GYRO_CONFIG      0x1B
00060 #define ACCEL_CONFIG     0x1C
00061 #define ACCEL_CONFIG2    0x1D
00062 #define LP_ACCEL_ODR     0x1E
00063 #define WOM_THR          0x1F
00064 
00065 #define MOT_DUR          0x20  // Duration counter threshold for motion interrupt generation, 1 kHz rate, LSB = 1 ms
00066 #define ZMOT_THR         0x21  // Zero-motion detection threshold bits [7:0]
00067 #define ZRMOT_DUR        0x22  // Duration counter threshold for zero motion interrupt generation, 16 Hz rate, LSB = 64 ms
00068 
00069 #define FIFO_EN          0x23
00070 #define I2C_MST_CTRL     0x24
00071 #define I2C_SLV0_ADDR    0x25
00072 #define I2C_SLV0_REG     0x26
00073 #define I2C_SLV0_CTRL    0x27
00074 #define I2C_SLV1_ADDR    0x28
00075 #define I2C_SLV1_REG     0x29
00076 #define I2C_SLV1_CTRL    0x2A
00077 #define I2C_SLV2_ADDR    0x2B
00078 #define I2C_SLV2_REG     0x2C
00079 #define I2C_SLV2_CTRL    0x2D
00080 #define I2C_SLV3_ADDR    0x2E
00081 #define I2C_SLV3_REG     0x2F
00082 #define I2C_SLV3_CTRL    0x30
00083 #define I2C_SLV4_ADDR    0x31
00084 #define I2C_SLV4_REG     0x32
00085 #define I2C_SLV4_DO      0x33
00086 #define I2C_SLV4_CTRL    0x34
00087 #define I2C_SLV4_DI      0x35
00088 #define I2C_MST_STATUS   0x36
00089 #define INT_PIN_CFG      0x37
00090 #define INT_ENABLE       0x38
00091 #define DMP_INT_STATUS   0x39  // Check DMP interrupt
00092 #define INT_STATUS       0x3A
00093 #define ACCEL_XOUT_H     0x3B
00094 #define ACCEL_XOUT_L     0x3C
00095 #define ACCEL_YOUT_H     0x3D
00096 #define ACCEL_YOUT_L     0x3E
00097 #define ACCEL_ZOUT_H     0x3F
00098 #define ACCEL_ZOUT_L     0x40
00099 #define TEMP_OUT_H       0x41
00100 #define TEMP_OUT_L       0x42
00101 #define GYRO_XOUT_H      0x43
00102 #define GYRO_XOUT_L      0x44
00103 #define GYRO_YOUT_H      0x45
00104 #define GYRO_YOUT_L      0x46
00105 #define GYRO_ZOUT_H      0x47
00106 #define GYRO_ZOUT_L      0x48
00107 #define EXT_SENS_DATA_00 0x49
00108 #define EXT_SENS_DATA_01 0x4A
00109 #define EXT_SENS_DATA_02 0x4B
00110 #define EXT_SENS_DATA_03 0x4C
00111 #define EXT_SENS_DATA_04 0x4D
00112 #define EXT_SENS_DATA_05 0x4E
00113 #define EXT_SENS_DATA_06 0x4F
00114 #define EXT_SENS_DATA_07 0x50
00115 #define EXT_SENS_DATA_08 0x51
00116 #define EXT_SENS_DATA_09 0x52
00117 #define EXT_SENS_DATA_10 0x53
00118 #define EXT_SENS_DATA_11 0x54
00119 #define EXT_SENS_DATA_12 0x55
00120 #define EXT_SENS_DATA_13 0x56
00121 #define EXT_SENS_DATA_14 0x57
00122 #define EXT_SENS_DATA_15 0x58
00123 #define EXT_SENS_DATA_16 0x59
00124 #define EXT_SENS_DATA_17 0x5A
00125 #define EXT_SENS_DATA_18 0x5B
00126 #define EXT_SENS_DATA_19 0x5C
00127 #define EXT_SENS_DATA_20 0x5D
00128 #define EXT_SENS_DATA_21 0x5E
00129 #define EXT_SENS_DATA_22 0x5F
00130 #define EXT_SENS_DATA_23 0x60
00131 #define MOT_DETECT_STATUS 0x61
00132 #define I2C_SLV0_DO      0x63
00133 #define I2C_SLV1_DO      0x64
00134 #define I2C_SLV2_DO      0x65
00135 #define I2C_SLV3_DO      0x66
00136 #define I2C_MST_DELAY_CTRL 0x67
00137 #define SIGNAL_PATH_RESET  0x68
00138 #define MOT_DETECT_CTRL  0x69
00139 #define USER_CTRL        0x6A  // Bit 7 enable DMP, bit 3 reset DMP
00140 #define PWR_MGMT_1       0x6B // Device defaults to the SLEEP mode
00141 #define PWR_MGMT_2       0x6C
00142 #define DMP_BANK         0x6D  // Activates a specific bank in the DMP
00143 #define DMP_RW_PNT       0x6E  // Set read/write pointer to a specific start address in specified DMP bank
00144 #define DMP_REG          0x6F  // Register in DMP from which to read or to which to write
00145 #define DMP_REG_1        0x70
00146 #define DMP_REG_2        0x71
00147 #define FIFO_COUNTH      0x72
00148 #define FIFO_COUNTL      0x73
00149 #define FIFO_R_W         0x74
00150 #define WHO_AM_I_MPU9250 0x75 // Should return 0x71
00151 #define XA_OFFSET_H      0x77
00152 #define XA_OFFSET_L      0x78
00153 #define YA_OFFSET_H      0x7A
00154 #define YA_OFFSET_L      0x7B
00155 #define ZA_OFFSET_H      0x7D
00156 #define ZA_OFFSET_L      0x7E
00157 
00158 // Seven-bit device address is 110100 for ADO = 0 and 110101 for ADO = 1
00159 //mbed uses the eight-bit device address, so shift seven-bit addresses left by one!
00160 #define ADO 0
00161 #if ADO
00162 #define MPU9250_ADDRESS 0x69<<1  // Device address when ADO = 1
00163 #else
00164 #define MPU9250_ADDRESS 0x68<<1  // Device address when ADO = 0
00165 #endif
00166 
00167 // Set initial input parameters
00168 enum Ascale {
00169   AFS_2G = 0,
00170   AFS_4G,
00171   AFS_8G,
00172   AFS_16G
00173 };
00174 
00175 enum Gscale {
00176   GFS_250DPS = 0,
00177   GFS_500DPS,
00178   GFS_1000DPS,
00179   GFS_2000DPS
00180 };
00181 
00182 enum Mscale {
00183   MFS_14BITS = 0, // 0.6 mG per LSB
00184   MFS_16BITS      // 0.15 mG per LSB
00185 };
00186 
00187 uint8_t Ascale = AFS_2G;     // AFS_2G, AFS_4G, AFS_8G, AFS_16G
00188 uint8_t Gscale = GFS_250DPS; // GFS_250DPS, GFS_500DPS, GFS_1000DPS, GFS_2000DPS
00189 uint8_t Mscale = MFS_16BITS; // MFS_14BITS or MFS_16BITS, 14-bit or 16-bit magnetometer resolution
00190 uint8_t Mmode = 0x06;        // Either 8 Hz 0x02) or 100 Hz (0x06) magnetometer data ODR
00191 float aRes, gRes, mRes;      // scale resolutions per LSB for the sensors
00192 
00193 //Set up I2C, (SDA,SCL)
00194 I2C i2c(p9, p10);
00195 
00196 // Pin definitions
00197 int16_t accelCount[3];  // Stores the 16-bit signed accelerometer sensor output
00198 int16_t gyroCount[3];   // Stores the 16-bit signed gyro sensor output
00199 int16_t magCount[3];    // Stores the 16-bit signed magnetometer sensor output
00200 float magCalibration[3] = {0, 0, 0}, magbias[3] = {0, 0, 0};  // Factory mag calibration and mag bias
00201 float gyroBias[3] = {0, 0, 0}, accelBias[3] = {0, 0, 0}; // Bias corrections for gyro and accelerometer
00202 float ax, ay, az, gx, gy, gz, mx, my, mz; // variables to hold latest sensor data values
00203 float th_ax, th_ay, th_az;
00204 float th_ax_LPF, th_ay_LPF, th_az_LPF;
00205 float pre_th_ax, pre_th_ay, pre_th_az;
00206 float th_gx, th_gy, th_gz;
00207 float pre_gx, pre_gy, pre_gz;
00208 float th_x, th_y, th_z, th_x_d, th_y_d, th_z_d;
00209 int16_t tempCount;   // Stores the real internal chip temperature in degrees Celsius
00210 float temperature;
00211 float SelfTest[6];
00212 
00213 float delt_t = 0.0f; // used to display output rate
00214 float sum_dt = 0.0f; //
00215 float dt0_ekf, dt1_ekf, dt0_mwf, dt1_mwf;
00216 
00217 // parameters for 6 DoF sensor fusion calculations
00218 float PI = 3.14159265358979323846f;
00219 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
00220 float beta = sqrt(3.0f / 4.0f) * GyroMeasError;  // compute beta
00221 float GyroMeasDrift = PI * (1.0f / 180.0f);      // gyroscope measurement drift in rad/s/s (start at 0.0 deg/s/s)
00222 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
00223 #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
00224 #define Ki 0.0f
00225 
00226 float pitch, yaw, roll;
00227 float pre_pitch, pre_roll;
00228 float lastUpdate = 0.0f, firstUpdate = 0.0f, Now = 0.0f;  // used to calculate integration interval                               // used to calculate integration interval
00229 float q[4] = {1.0f, 0.0f, 0.0f, 0.0f};           // vector to hold quaternion
00230 float q1 = 1.0f;
00231 float q2 = 0.0f;
00232 float q3 = 0.0f;
00233 float q4 = 0.0f;
00234 float eInt[3] = {0.0f, 0.0f, 0.0f};              // vector to hold integral error for Mahony method
00235 
00236 class MPU9250 {
00237 
00238     protected:
00239 
00240     public:
00241   //===================================================================================================================
00242 //====== Set of useful function to access acceleratio, gyroscope, and temperature data
00243 //===================================================================================================================
00244 
00245     void writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
00246 {
00247    char data_write[2];
00248    data_write[0] = subAddress;
00249    data_write[1] = data;
00250    i2c.write(address, data_write, 2, 0);
00251 }
00252 
00253     char readByte(uint8_t address, uint8_t subAddress)
00254 {
00255     char data[1]; // `data` will store the register data
00256     char data_write[1];
00257     data_write[0] = subAddress;
00258     i2c.write(address, data_write, 1, 1); // no stop
00259     i2c.read(address, data, 1, 0);
00260     return data[0];
00261 }
00262 
00263     void readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
00264 {
00265     char data[14];
00266     char data_write[1];
00267     data_write[0] = subAddress;
00268     i2c.write(address, data_write, 1, 1); // no stop
00269     i2c.read(address, data, count, 0);
00270     for(int ii = 0; ii < count; ii++) {
00271      dest[ii] = data[ii];
00272     }
00273 }
00274 
00275 void getMres() {
00276   switch (Mscale)
00277   {
00278     // Possible magnetometer scales (and their register bit settings) are:
00279     // 14 bit resolution (0) and 16 bit resolution (1)
00280     case MFS_14BITS:
00281           mRes = 10.0*4219.0/8190.0; // Proper scale to return milliGauss
00282           break;
00283     case MFS_16BITS:
00284           mRes = 10.0*4219.0/32760.0; // Proper scale to return milliGauss
00285           break;
00286   }
00287 }
00288 
00289 void getGres() {
00290   switch (Gscale)
00291   {
00292     // Possible gyro scales (and their register bit settings) are:
00293     // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS  (11).
00294         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00295     case GFS_250DPS:
00296           gRes = 250.0/32768.0;
00297           break;
00298     case GFS_500DPS:
00299           gRes = 500.0/32768.0;
00300           break;
00301     case GFS_1000DPS:
00302           gRes = 1000.0/32768.0;
00303           break;
00304     case GFS_2000DPS:
00305           gRes = 2000.0/32768.0;
00306           break;
00307   }
00308 }
00309 
00310 void getAres() {
00311   switch (Ascale)
00312   {
00313     // Possible accelerometer scales (and their register bit settings) are:
00314     // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs  (11).
00315         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00316     case AFS_2G:
00317           aRes = 2.0/32768.0;
00318           break;
00319     case AFS_4G:
00320           aRes = 4.0/32768.0;
00321           break;
00322     case AFS_8G:
00323           aRes = 8.0/32768.0;
00324           break;
00325     case AFS_16G:
00326           aRes = 16.0/32768.0;
00327           break;
00328   }
00329 }
00330 
00331 
00332 void readAccelData(int16_t * destination)
00333 {
00334   uint8_t rawData[6];  // x/y/z accel register data stored here
00335   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
00336   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00337   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00338   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00339 }
00340 
00341 void readGyroData(int16_t * destination)
00342 {
00343   uint8_t rawData[6];  // x/y/z gyro register data stored here
00344   readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
00345   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00346   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00347   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00348 }
00349 
00350 void readMagData(int16_t * destination)
00351 {
00352   uint8_t rawData[7];  // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition
00353   if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set
00354   readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]);  // Read the six raw data and ST2 registers sequentially into data array
00355   uint8_t c = rawData[6]; // End data read by reading ST2 register
00356     if(!(c & 0x08))
00357     { // Check if magnetic sensor overflow set, if not then report data
00358     destination[0] = (int16_t)(((int16_t)rawData[1] << 8) | rawData[0]);  // Turn the MSB and LSB into a signed 16-bit value
00359     destination[1] = (int16_t)(((int16_t)rawData[3] << 8) | rawData[2]) ;  // Data stored as little Endian
00360     destination[2] = (int16_t)(((int16_t)rawData[5] << 8) | rawData[4]) ;
00361     }
00362   }
00363 }
00364 
00365 int16_t readTempData()
00366 {
00367   uint8_t rawData[2];  // x/y/z gyro register data stored here
00368   readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]);  // Read the two raw data registers sequentially into data array
00369   return (int16_t)(((int16_t)rawData[0]) << 8 | rawData[1]) ;  // Turn the MSB and LSB into a 16-bit value
00370 }
00371 
00372 
00373 void resetMPU9250()
00374 {
00375   // reset device
00376   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00377   wait(0.1);
00378 }
00379 
00380   void initAK8963(float * destination)
00381 {
00382   // First extract the factory calibration for each magnetometer axis
00383   uint8_t rawData[3];  // x/y/z gyro calibration data stored here
00384   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer
00385   wait(0.01);
00386   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode
00387   wait(0.01);
00388   readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
00389   destination[0] =  (float)(rawData[0] - 128)/256.0f + 1.0f;   // Return x-axis sensitivity adjustment values, etc.
00390   destination[1] =  (float)(rawData[1] - 128)/256.0f + 1.0f;
00391   destination[2] =  (float)(rawData[2] - 128)/256.0f + 1.0f;
00392   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer
00393   wait(0.01);
00394   // Configure the magnetometer for continuous read and highest resolution
00395   // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register,
00396   // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates
00397   writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR
00398   wait(0.01);
00399 }
00400 
00401 
00402 void initMPU9250()
00403 {
00404  // Initialize MPU9250 device
00405  // wake up device
00406   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors
00407   wait(0.1); // Delay 100 ms for PLL to get established on x-axis gyro; should check for PLL ready interrupt
00408 
00409  // get stable time source
00410   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00411 
00412  // Configure Gyro and Accelerometer
00413  // Disable FSYNC and set accelerometer and gyro bandwidth to 44 and 42 Hz, respectively;
00414  // DLPF_CFG = bits 2:0 = 010; this sets the sample rate at 1 kHz for both
00415  // Maximum delay is 4.9 ms which is just over a 200 Hz maximum rate
00416   writeByte(MPU9250_ADDRESS, CONFIG, 0x03);
00417 
00418  // Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV)
00419   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04);  // Use a 200 Hz rate; the same rate set in CONFIG above
00420 
00421  // Set gyroscope full scale range
00422  // Range selects FS_SEL and AFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
00423   uint8_t c =  readByte(MPU9250_ADDRESS, GYRO_CONFIG);
00424   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0xE0); // Clear self-test bits [7:5]
00425   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
00426   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c | Gscale << 3); // Set full scale range for the gyro
00427 
00428  // Set accelerometer configuration
00429   c =  readByte(MPU9250_ADDRESS, ACCEL_CONFIG);
00430   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0xE0); // Clear self-test bits [7:5]
00431   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
00432   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c | Ascale << 3); // Set full scale range for the accelerometer
00433 
00434  // Set accelerometer sample rate configuration
00435  // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for
00436  // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz
00437   c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2);
00438   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c & ~0x0F); // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])
00439   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c | 0x03); // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
00440 
00441  // The accelerometer, gyro, and thermometer are set to 1 kHz sample rates,
00442  // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting
00443 
00444   // Configure Interrupts and Bypass Enable
00445   // Set interrupt pin active high, push-pull, and clear on read of INT_STATUS, enable I2C_BYPASS_EN so additional chips
00446   // can join the I2C bus and all can be controlled by the Arduino as master
00447    writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22);
00448    writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
00449 }
00450 
00451 // Function which accumulates gyro and accelerometer data after device initialization. It calculates the average
00452 // of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers.
00453 void calibrateMPU9250(float * dest1, float * dest2)
00454 {
00455   uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data
00456   uint16_t ii, packet_count, fifo_count;
00457   int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};
00458 
00459 // reset device, reset all registers, clear gyro and accelerometer bias registers
00460   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00461   wait(0.1);
00462 
00463 // get stable time source
00464 // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00465   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);
00466   writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00);
00467   wait(0.2);
00468 
00469 // Configure device for bias calculation
00470   writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00);   // Disable all interrupts
00471   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);      // Disable FIFO
00472   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00);   // Turn on internal clock source
00473   writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master
00474   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00);    // Disable FIFO and I2C master modes
00475   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C);    // Reset FIFO and DMP
00476   wait(0.015);
00477 
00478 // Configure MPU9250 gyro and accelerometer for bias calculation
00479   writeByte(MPU9250_ADDRESS, CONFIG, 0x01);      // Set low-pass filter to 188 Hz
00480   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00);  // Set sample rate to 1 kHz
00481   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);  // Set gyro full-scale to 250 degrees per second, maximum sensitivity
00482   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity
00483 
00484   uint16_t  gyrosensitivity  = 131;   // = 131 LSB/degrees/sec
00485   uint16_t  accelsensitivity = 16384;  // = 16384 LSB/g
00486 
00487 // Configure FIFO to capture accelerometer and gyro data for bias calculation
00488   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40);   // Enable FIFO
00489   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78);     // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9250)
00490   wait(0.04); // accumulate 40 samples in 80 milliseconds = 480 bytes
00491 
00492 // At end of sample accumulation, turn off FIFO sensor read
00493   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);        // Disable gyro and accelerometer sensors for FIFO
00494   readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count
00495   fifo_count = ((uint16_t)data[0] << 8) | data[1];
00496   packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging
00497 
00498   for (ii = 0; ii < packet_count; ii++)
00499   {
00500     int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0};
00501     readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging
00502     accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1]  ) ;  // Form signed 16-bit integer for each sample in FIFO
00503     accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3]  ) ;
00504     accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5]  ) ;
00505     gyro_temp[0]  = (int16_t) (((int16_t)data[6] << 8) | data[7]  ) ;
00506     gyro_temp[1]  = (int16_t) (((int16_t)data[8] << 8) | data[9]  ) ;
00507     gyro_temp[2]  = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;
00508 
00509     accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
00510     accel_bias[1] += (int32_t) accel_temp[1];
00511     accel_bias[2] += (int32_t) accel_temp[2];
00512     gyro_bias[0]  += (int32_t) gyro_temp[0];
00513     gyro_bias[1]  += (int32_t) gyro_temp[1];
00514     gyro_bias[2]  += (int32_t) gyro_temp[2];
00515     }
00516 
00517     accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases
00518     accel_bias[1] /= (int32_t) packet_count;
00519     accel_bias[2] /= (int32_t) packet_count;
00520     gyro_bias[0]  /= (int32_t) packet_count;
00521     gyro_bias[1]  /= (int32_t) packet_count;
00522     gyro_bias[2]  /= (int32_t) packet_count;
00523 
00524     if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;}  // Remove gravity from the z-axis accelerometer bias calculation
00525     else {accel_bias[2] += (int32_t) accelsensitivity;}
00526 
00527     // Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup
00528     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
00529     data[1] = (-gyro_bias[0]/4)       & 0xFF; // Biases are additive, so change sign on calculated average gyro biases
00530     data[2] = (-gyro_bias[1]/4  >> 8) & 0xFF;
00531     data[3] = (-gyro_bias[1]/4)       & 0xFF;
00532     data[4] = (-gyro_bias[2]/4  >> 8) & 0xFF;
00533     data[5] = (-gyro_bias[2]/4)       & 0xFF;
00534 
00535 /// Push gyro biases to hardware registers
00536 /*  writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]);
00537   writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]);
00538   writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]);
00539   writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]);
00540   writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]);
00541   writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);
00542 */
00543     dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; // construct gyro bias in deg/s for later manual subtraction
00544     dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity;
00545     dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;
00546 
00547 // Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain
00548 // factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold
00549 // non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature
00550 // compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that
00551 // the accelerometer biases calculated above must be divided by 8.
00552 
00553     int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases
00554     readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values
00555     accel_bias_reg[0] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00556     readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]);
00557     accel_bias_reg[1] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00558     readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
00559     accel_bias_reg[2] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00560 
00561     uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers
00562     uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis
00563 
00564     for(ii = 0; ii < 3; ii++)
00565     {
00566         if(accel_bias_reg[ii] & mask) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit
00567     }
00568 
00569     // Construct total accelerometer bias, including calculated average accelerometer bias from above
00570     accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale)
00571     accel_bias_reg[1] -= (accel_bias[1]/8);
00572     accel_bias_reg[2] -= (accel_bias[2]/8);
00573 
00574     data[0] = (accel_bias_reg[0] >> 8) & 0xFF;
00575     data[1] = (accel_bias_reg[0])      & 0xFF;
00576     data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00577     data[2] = (accel_bias_reg[1] >> 8) & 0xFF;
00578     data[3] = (accel_bias_reg[1])      & 0xFF;
00579     data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00580     data[4] = (accel_bias_reg[2] >> 8) & 0xFF;
00581     data[5] = (accel_bias_reg[2])      & 0xFF;
00582     data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00583 
00584 // Apparently this is not working for the acceleration biases in the MPU-9250
00585 // Are we handling the temperature correction bit properly?
00586 // Push accelerometer biases to hardware registers
00587 /*  writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]);
00588   writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]);
00589   writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]);
00590   writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]);
00591   writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]);
00592   writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);
00593 */
00594   // Output scaled accelerometer biases for manual subtraction in the main program
00595      dest2[0] = (float)accel_bias[0]/(float)accelsensitivity;
00596      dest2[1] = (float)accel_bias[1]/(float)accelsensitivity;
00597      dest2[2] = (float)accel_bias[2]/(float)accelsensitivity;
00598   }
00599 
00600 
00601   // Accelerometer and gyroscope self test; check calibration wrt factory settings
00602   void MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass
00603   {
00604      uint8_t rawData[6] = {0, 0, 0, 0, 0, 0};
00605      uint8_t selfTest[6];
00606      int16_t gAvg[3], aAvg[3], aSTAvg[3], gSTAvg[3];
00607      float factoryTrim[6];
00608      uint8_t FS = 0;
00609 
00610     writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz
00611     writeByte(MPU9250_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz
00612     writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 1<<FS); // Set full scale range for the gyro to 250 dps
00613     writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz
00614     writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 1<<FS); // Set full scale range for the accelerometer to 2 g
00615 
00616     for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer
00617 
00618     readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00619     aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00620     aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00621     aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00622 
00623       readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00624     gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00625     gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00626     gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00627     }
00628 
00629     for (int ii =0; ii < 3; ii++)
00630     {
00631     // Get average of 200 values and store as average current readings
00632     aAvg[ii] /= 200;
00633     gAvg[ii] /= 200;
00634     }
00635 
00636   // Configure the accelerometer for self-test
00637      writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g
00638      writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s
00639      //delay(25); // Delay a while to let the device stabilize
00640 
00641     for( int ii = 0; ii < 200; ii++)
00642     {
00643     // get average self-test values of gyro and acclerometer
00644     readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00645     aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00646     aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00647     aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00648 
00649     readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00650     gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00651     gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00652     gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00653     }
00654 
00655     for (int ii =0; ii < 3; ii++)
00656     {
00657     // Get average of 200 values and store as average self-test readings
00658     aSTAvg[ii] /= 200;
00659     gSTAvg[ii] /= 200;
00660     }
00661 
00662    // Configure the gyro and accelerometer for normal operation
00663      writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00);
00664      writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);
00665      //delay(25); // Delay a while to let the device stabilize
00666 
00667      // Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg
00668      selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results
00669      selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results
00670      selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results
00671      selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results
00672      selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results
00673      selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results
00674 
00675     // Retrieve factory self-test value from self-test code reads
00676      factoryTrim[0] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation
00677      factoryTrim[1] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation
00678      factoryTrim[2] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation
00679      factoryTrim[3] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation
00680      factoryTrim[4] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation
00681      factoryTrim[5] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation
00682 
00683    // Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response
00684    // To get percent, must multiply by 100
00685      for (int i = 0; i < 3; i++)
00686      {
00687        destination[i] = 100.0*((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i]; // Report percent differences
00688        destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3]; // Report percent differences
00689      }
00690 
00691   }
00692 
00693   void MadgwickFilterUpdate_6axis(float ax, float ay, float az, float wx, float wy, float wz)
00694   {
00695     // Local system variables
00696     float norm; // vector norm
00697     float SEqDot_omega_1, SEqDot_omega_2, SEqDot_omega_3, SEqDot_omega_4; // quaternion derrivative from gyroscopes elements
00698     float f_1, f_2, f_3; // objective function elements
00699     float J_11or24, J_12or23, J_13or22, J_14or21, J_32, J_33; // objective function Jacobian elements
00700     float SEqHatDot_1, SEqHatDot_2, SEqHatDot_3, SEqHatDot_4; // estimated direction of the gyroscope error
00701 
00702     // Axulirary variables to avoid reapeated calcualtions
00703     float halfSEq_1 = 0.5f * q1;
00704     float halfSEq_2 = 0.5f * q2;
00705     float halfSEq_3 = 0.5f * q3;
00706     float halfSEq_4 = 0.5f * q4;
00707     float twoSEq_1 = 2.0f * q1;
00708     float twoSEq_2 = 2.0f * q2;
00709     float twoSEq_3 = 2.0f * q3;
00710 
00711     // Normalise the accelerometer measurement
00712     norm = sqrt(ax * ax + ay * ay + az * az);
00713     ax /= norm;
00714     ay /= norm;
00715     az /= norm;
00716 
00717     // Compute the objective function and Jacobian
00718     f_1 = twoSEq_2 * q4 - twoSEq_1 * q3 - ax;
00719     f_2 = twoSEq_1 * q2 + twoSEq_3 * q4 - ay;
00720     f_3 = 1.0f - twoSEq_2 * q2 - twoSEq_3 * q3 - az;
00721     J_11or24 = twoSEq_3; // J_11 negated in matrix multiplication
00722     J_12or23 = 2.0f * q4;
00723     J_13or22 = twoSEq_1; // J_12 negated in matrix multiplication
00724     J_14or21 = twoSEq_2;
00725     J_32 = 2.0f * J_14or21; // negated in matrix multiplication
00726     J_33 = 2.0f * J_11or24; // negated in matrix multiplication
00727 
00728     // Compute the gradient (matrix multiplication)
00729     SEqHatDot_1 = J_14or21 * f_2 - J_11or24 * f_1;
00730     SEqHatDot_2 = J_12or23 * f_1 + J_13or22 * f_2 - J_32 * f_3;
00731     SEqHatDot_3 = J_12or23 * f_2 - J_33 * f_3 - J_13or22 * f_1;
00732     SEqHatDot_4 = J_14or21 * f_1 + J_11or24 * f_2;
00733 
00734     // Normalise the gradient
00735     norm = sqrt(SEqHatDot_1 * SEqHatDot_1 + SEqHatDot_2 * SEqHatDot_2 + SEqHatDot_3 * SEqHatDot_3 + SEqHatDot_4 * SEqHatDot_4);
00736     SEqHatDot_1 /= norm;
00737     SEqHatDot_2 /= norm;
00738     SEqHatDot_3 /= norm;
00739     SEqHatDot_4 /= norm;
00740 
00741     // Compute the quaternion derrivative measured by gyroscopes
00742     SEqDot_omega_1 = -halfSEq_2 * wx - halfSEq_3 * wy - halfSEq_4 * wz;
00743     SEqDot_omega_2 = halfSEq_1 * wx + halfSEq_3 * wz - halfSEq_4 * wy;
00744     SEqDot_omega_3 = halfSEq_1 * wy - halfSEq_2 * wz + halfSEq_4 * wx;
00745     SEqDot_omega_4 = halfSEq_1 * wz + halfSEq_2 * wy - halfSEq_3 * wx;
00746 
00747     // Compute then integrate the estimated quaternion derrivative
00748     q1 += (SEqDot_omega_1 - (beta * SEqHatDot_1)) * delt_t;
00749     q2 += (SEqDot_omega_2 - (beta * SEqHatDot_2)) * delt_t;
00750     q3 += (SEqDot_omega_3 - (beta * SEqHatDot_3)) * delt_t;
00751     q4 += (SEqDot_omega_4 - (beta * SEqHatDot_4)) * delt_t;
00752 
00753     // Normalise quaternion
00754     norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);
00755     q1 /= norm;
00756     q2 /= norm;
00757     q3 /= norm;
00758     q4 /= norm;
00759 
00760   }
00761 
00762 
00763 
00764  // Similar to Madgwick scheme but uses proportional and integral filtering on the error between estimated reference vectors and
00765  // measured ones.
00766         /*
00767         void MahonyQuaternionUpdate(float ax, float ay, float az, float gx, float gy, float gz, float mx, float my, float mz)
00768         {
00769             float q1 = q[0], q2 = q[1], q3 = q[2], q4 = q[3];   // short name local variable for readability
00770             float norm;
00771             float hx, hy, bx, bz;
00772             float vx, vy, vz, wx, wy, wz;
00773             float ex, ey, ez;
00774             float pa, pb, pc;
00775 
00776             // Auxiliary variables to avoid repeated arithmetic
00777             float q1q1 = q1 * q1;
00778             float q1q2 = q1 * q2;
00779             float q1q3 = q1 * q3;
00780             float q1q4 = q1 * q4;
00781             float q2q2 = q2 * q2;
00782             float q2q3 = q2 * q3;
00783             float q2q4 = q2 * q4;
00784             float q3q3 = q3 * q3;
00785             float q3q4 = q3 * q4;
00786             float q4q4 = q4 * q4;
00787 
00788             // Normalise accelerometer measurement
00789             norm = sqrt(ax * ax + ay * ay + az * az);
00790             if (norm == 0.0f) return; // handle NaN
00791             norm = 1.0f / norm;        // use reciprocal for division
00792             ax *= norm;
00793             ay *= norm;
00794             az *= norm;
00795 
00796             // Normalise magnetometer measurement
00797             norm = sqrt(mx * mx + my * my + mz * mz);
00798             if (norm == 0.0f) return; // handle NaN
00799             norm = 1.0f / norm;        // use reciprocal for division
00800             mx *= norm;
00801             my *= norm;
00802             mz *= norm;
00803 
00804             // Reference direction of Earth's magnetic field
00805             hx = 2.0f * mx * (0.5f - q3q3 - q4q4) + 2.0f * my * (q2q3 - q1q4) + 2.0f * mz * (q2q4 + q1q3);
00806             hy = 2.0f * mx * (q2q3 + q1q4) + 2.0f * my * (0.5f - q2q2 - q4q4) + 2.0f * mz * (q3q4 - q1q2);
00807             bx = sqrt((hx * hx) + (hy * hy));
00808             bz = 2.0f * mx * (q2q4 - q1q3) + 2.0f * my * (q3q4 + q1q2) + 2.0f * mz * (0.5f - q2q2 - q3q3);
00809 
00810             // Estimated direction of gravity and magnetic field
00811             vx = 2.0f * (q2q4 - q1q3);
00812             vy = 2.0f * (q1q2 + q3q4);
00813             vz = q1q1 - q2q2 - q3q3 + q4q4;
00814             wx = 2.0f * bx * (0.5f - q3q3 - q4q4) + 2.0f * bz * (q2q4 - q1q3);
00815             wy = 2.0f * bx * (q2q3 - q1q4) + 2.0f * bz * (q1q2 + q3q4);
00816             wz = 2.0f * bx * (q1q3 + q2q4) + 2.0f * bz * (0.5f - q2q2 - q3q3);
00817 
00818             // Error is cross product between estimated direction and measured direction of gravity
00819             ex = (ay * vz - az * vy) + (my * wz - mz * wy);
00820             ey = (az * vx - ax * vz) + (mz * wx - mx * wz);
00821             ez = (ax * vy - ay * vx) + (mx * wy - my * wx);
00822             if (Ki > 0.0f)
00823             {
00824                 eInt[0] += ex;      // accumulate integral error
00825                 eInt[1] += ey;
00826                 eInt[2] += ez;
00827             }
00828             else
00829             {
00830                 eInt[0] = 0.0f;     // prevent integral wind up
00831                 eInt[1] = 0.0f;
00832                 eInt[2] = 0.0f;
00833             }
00834 
00835             // Apply feedback terms
00836             gx = gx + Kp * ex + Ki * eInt[0];
00837             gy = gy + Kp * ey + Ki * eInt[1];
00838             gz = gz + Kp * ez + Ki * eInt[2];
00839 
00840             // Integrate rate of change of quaternion
00841             pa = q2;
00842             pb = q3;
00843             pc = q4;
00844             q1 = q1 + (-q2 * gx - q3 * gy - q4 * gz) * (0.5f * delt_t);
00845             q2 = pa + (q1 * gx + pb * gz - pc * gy) * (0.5f * delt_t);
00846             q3 = pb + (q1 * gy - pa * gz + pc * gx) * (0.5f * delt_t);
00847             q4 = pc + (q1 * gz + pa * gy - pb * gx) * (0.5f * delt_t);
00848 
00849             // Normalise quaternion
00850             norm = sqrt(q1 * q1 + q2 * q2 + q3 * q3 + q4 * q4);
00851             norm = 1.0f / norm;
00852             q[0] = q1 * norm;
00853             q[1] = q2 * norm;
00854             q[2] = q3 * norm;
00855             q[3] = q4 * norm;
00856 
00857         }
00858         */
00859   };
00860 #endif