MPU9250.cpp

00001 #include "MPU9250.h"
00002 
00003 #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
00004 #define Ki 0.0f
00005 
00006 //******************************************************************************
00007 MPU9250::MPU9250(PinName sda, PinName scl)
00008 {
00009     i2c_ = new I2C(sda, scl);
00010     i2c_->frequency(400000);
00011 }
00012 
00013 //******************************************************************************
00014 MPU9250::MPU9250(I2C *i2c):i2c_(i2c){}
00015 
00016 //******************************************************************************
00017 MPU9250::~MPU9250()
00018 {    
00019    delete i2c_;
00020 }
00021 
00022 void MPU9250::writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
00023 {
00024    char data_write[2];
00025    data_write[0] = subAddress;
00026    data_write[1] = data;
00027    i2c_->write(address, data_write, 2, 0);
00028 }
00029 
00030 char MPU9250::readByte(uint8_t address, uint8_t subAddress)
00031 {
00032     char data[1]; // `data` will store the register data     
00033     char data_write[1];
00034     data_write[0] = subAddress;
00035     i2c_->write(address, data_write, 1, 1); // no stop
00036     i2c_->read(address, data, 1, 0); 
00037     return data[0]; 
00038 }
00039 
00040 void MPU9250::readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
00041 {     
00042     char data[14];
00043     char data_write[1];
00044     data_write[0] = subAddress;
00045     i2c_->write(address, data_write, 1, 1); // no stop
00046     i2c_->read(address, data, count, 0); 
00047     for(int ii = 0; ii < count; ii++) {
00048      dest[ii] = data[ii];
00049     }
00050 } 
00051 
00052 void MPU9250::getMres() {
00053   switch (Mscale)
00054   {
00055     // Possible magnetometer scales (and their register bit settings) are:
00056     // 14 bit resolution (0) and 16 bit resolution (1)
00057     case MFS_14BITS:
00058           mRes = 10.0*4219.0/8190.0; // Proper scale to return milliGauss
00059           break;
00060     case MFS_16BITS:
00061           mRes = 10.0*4219.0/32760.0; // Proper scale to return milliGauss
00062           break;
00063   }
00064 }
00065 
00066 
00067 void MPU9250::getGres() {
00068   switch (Gscale)
00069   {
00070     // Possible gyro scales (and their register bit settings) are:
00071     // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS  (11). 
00072         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00073     case GFS_250DPS:
00074           gRes = 250.0/32768.0;
00075           break;
00076     case GFS_500DPS:
00077           gRes = 500.0/32768.0;
00078           break;
00079     case GFS_1000DPS:
00080           gRes = 1000.0/32768.0;
00081           break;
00082     case GFS_2000DPS:
00083           gRes = 2000.0/32768.0;
00084           break;
00085   }
00086 }
00087 
00088 
00089 void MPU9250::getAres() {
00090   switch (Ascale)
00091   {
00092     // Possible accelerometer scales (and their register bit settings) are:
00093     // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs  (11). 
00094         // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
00095     case AFS_2G:
00096           aRes = 2.0/32768.0;
00097           break;
00098     case AFS_4G:
00099           aRes = 4.0/32768.0;
00100           break;
00101     case AFS_8G:
00102           aRes = 8.0/32768.0;
00103           break;
00104     case AFS_16G:
00105           aRes = 16.0/32768.0;
00106           break;
00107   }
00108 }
00109 
00110 
00111 void MPU9250::readAccelData(int16_t * destination)
00112 {
00113   uint8_t rawData[6];  // x/y/z accel register data stored here
00114   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
00115   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00116   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
00117   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
00118 }
00119 
00120 void MPU9250::readGyroData(int16_t * destination)
00121 {
00122   uint8_t rawData[6];  // x/y/z gyro register data stored here
00123   readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
00124   destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
00125   destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
00126   destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
00127 }
00128 
00129 void MPU9250::readMagData(int16_t * destination)
00130 {
00131   uint8_t rawData[7];  // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition
00132   if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set
00133   readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]);  // Read the six raw data and ST2 registers sequentially into data array
00134   uint8_t c = rawData[6]; // End data read by reading ST2 register
00135     if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data
00136     destination[0] = (int16_t)(((int16_t)rawData[1] << 8) | rawData[0]);  // Turn the MSB and LSB into a signed 16-bit value
00137     destination[1] = (int16_t)(((int16_t)rawData[3] << 8) | rawData[2]) ;  // Data stored as little Endian
00138     destination[2] = (int16_t)(((int16_t)rawData[5] << 8) | rawData[4]) ; 
00139    }
00140   }
00141 }
00142 
00143 int16_t MPU9250::readTempData()
00144 {
00145   uint8_t rawData[2];  // x/y/z gyro register data stored here
00146   readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]);  // Read the two raw data registers sequentially into data array 
00147   return (int16_t)(((int16_t)rawData[0]) << 8 | rawData[1]) ;  // Turn the MSB and LSB into a 16-bit value
00148 }
00149 
00150 
00151 void MPU9250::resetMPU9250() {
00152   // reset device
00153   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00154   wait(0.1);
00155   }
00156   
00157 void MPU9250::initAK8963(float * destination)
00158 {
00159   // First extract the factory calibration for each magnetometer axis
00160   uint8_t rawData[3];  // x/y/z gyro calibration data stored here
00161   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
00162   wait(0.01);
00163   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode
00164   wait(0.01);
00165   readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
00166   destination[0] =  (float)(rawData[0] - 128)/256.0f + 1.0f;   // Return x-axis sensitivity adjustment values, etc.
00167   destination[1] =  (float)(rawData[1] - 128)/256.0f + 1.0f;  
00168   destination[2] =  (float)(rawData[2] - 128)/256.0f + 1.0f; 
00169   writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
00170   wait(0.01);
00171   // Configure the magnetometer for continuous read and highest resolution
00172   // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register,
00173   // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates
00174   writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR
00175   wait(0.01);
00176 }
00177 
00178 
00179 void MPU9250::initMPU9250()
00180 {  
00181  // Initialize MPU9250 device
00182  // wake up device
00183   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors 
00184   wait(0.1); // Delay 100 ms for PLL to get established on x-axis gyro; should check for PLL ready interrupt  
00185 
00186  // get stable time source
00187   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00188 
00189  // Configure Gyro and Accelerometer
00190  // Disable FSYNC and set accelerometer and gyro bandwidth to 44 and 42 Hz, respectively; 
00191  // DLPF_CFG = bits 2:0 = 010; this sets the sample rate at 1 kHz for both
00192  // Maximum delay is 4.9 ms which is just over a 200 Hz maximum rate
00193   writeByte(MPU9250_ADDRESS, CONFIG, 0x03);  
00194  
00195  // Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV)
00196   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04);  // Use a 200 Hz rate; the same rate set in CONFIG above
00197  
00198  // Set gyroscope full scale range
00199  // Range selects FS_SEL and AFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
00200   uint8_t c =  readByte(MPU9250_ADDRESS, GYRO_CONFIG);
00201   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0xE0); // Clear self-test bits [7:5] 
00202   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
00203   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c | Gscale << 3); // Set full scale range for the gyro
00204    
00205  // Set accelerometer configuration
00206   c =  readByte(MPU9250_ADDRESS, ACCEL_CONFIG);
00207   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0xE0); // Clear self-test bits [7:5] 
00208   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
00209   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c | Ascale << 3); // Set full scale range for the accelerometer 
00210 
00211  // Set accelerometer sample rate configuration
00212  // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for
00213  // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz
00214   c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2);
00215   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c & ~0x0F); // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])  
00216   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c | 0x03); // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
00217 
00218  // The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, 
00219  // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting
00220 
00221   // Configure Interrupts and Bypass Enable
00222   // Set interrupt pin active high, push-pull, and clear on read of INT_STATUS, enable I2C_BYPASS_EN so additional chips 
00223   // can join the I2C bus and all can be controlled by the Arduino as master
00224    writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22);    
00225    writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
00226 }
00227 
00228 // Function which accumulates gyro and accelerometer data after device initialization. It calculates the average
00229 // of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers.
00230 void MPU9250::calibrateMPU9250(float * dest1, float * dest2)
00231 {  
00232   uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data
00233   uint16_t ii, packet_count, fifo_count;
00234   int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};
00235   
00236 // reset device, reset all registers, clear gyro and accelerometer bias registers
00237   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
00238   wait(0.1);  
00239    
00240 // get stable time source
00241 // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
00242   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  
00243   writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00); 
00244   wait(0.2);
00245   
00246 // Configure device for bias calculation
00247   writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00);   // Disable all interrupts
00248   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);      // Disable FIFO
00249   writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00);   // Turn on internal clock source
00250   writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master
00251   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00);    // Disable FIFO and I2C master modes
00252   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C);    // Reset FIFO and DMP
00253   wait(0.015);
00254   
00255 // Configure MPU9250 gyro and accelerometer for bias calculation
00256   writeByte(MPU9250_ADDRESS, CONFIG, 0x01);      // Set low-pass filter to 188 Hz
00257   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00);  // Set sample rate to 1 kHz
00258   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);  // Set gyro full-scale to 250 degrees per second, maximum sensitivity
00259   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity
00260  
00261   uint16_t  gyrosensitivity  = 131;   // = 131 LSB/degrees/sec
00262   uint16_t  accelsensitivity = 16384;  // = 16384 LSB/g
00263 
00264 // Configure FIFO to capture accelerometer and gyro data for bias calculation
00265   writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40);   // Enable FIFO  
00266   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78);     // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9250)
00267   wait(0.04); // accumulate 40 samples in 80 milliseconds = 480 bytes
00268 
00269 // At end of sample accumulation, turn off FIFO sensor read
00270   writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);        // Disable gyro and accelerometer sensors for FIFO
00271   readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count
00272   fifo_count = ((uint16_t)data[0] << 8) | data[1];
00273   packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging
00274 
00275   for (ii = 0; ii < packet_count; ii++) {
00276     int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0};
00277     readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging
00278     accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1]  ) ;  // Form signed 16-bit integer for each sample in FIFO
00279     accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3]  ) ;
00280     accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5]  ) ;    
00281     gyro_temp[0]  = (int16_t) (((int16_t)data[6] << 8) | data[7]  ) ;
00282     gyro_temp[1]  = (int16_t) (((int16_t)data[8] << 8) | data[9]  ) ;
00283     gyro_temp[2]  = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;
00284     
00285     accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
00286     accel_bias[1] += (int32_t) accel_temp[1];
00287     accel_bias[2] += (int32_t) accel_temp[2];
00288     gyro_bias[0]  += (int32_t) gyro_temp[0];
00289     gyro_bias[1]  += (int32_t) gyro_temp[1];
00290     gyro_bias[2]  += (int32_t) gyro_temp[2];
00291             
00292 }
00293     accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases
00294     accel_bias[1] /= (int32_t) packet_count;
00295     accel_bias[2] /= (int32_t) packet_count;
00296     gyro_bias[0]  /= (int32_t) packet_count;
00297     gyro_bias[1]  /= (int32_t) packet_count;
00298     gyro_bias[2]  /= (int32_t) packet_count;
00299     
00300   if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;}  // Remove gravity from the z-axis accelerometer bias calculation
00301   else {accel_bias[2] += (int32_t) accelsensitivity;}
00302  
00303 // Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup
00304   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
00305   data[1] = (-gyro_bias[0]/4)       & 0xFF; // Biases are additive, so change sign on calculated average gyro biases
00306   data[2] = (-gyro_bias[1]/4  >> 8) & 0xFF;
00307   data[3] = (-gyro_bias[1]/4)       & 0xFF;
00308   data[4] = (-gyro_bias[2]/4  >> 8) & 0xFF;
00309   data[5] = (-gyro_bias[2]/4)       & 0xFF;
00310 
00311 /// Push gyro biases to hardware registers
00312 /*  writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]);
00313   writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]);
00314   writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]);
00315   writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]);
00316   writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]);
00317   writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);
00318 */
00319   dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; // construct gyro bias in deg/s for later manual subtraction
00320   dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity;
00321   dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;
00322 
00323 // Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain
00324 // factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold
00325 // non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature
00326 // compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that
00327 // the accelerometer biases calculated above must be divided by 8.
00328 
00329   int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases
00330   readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values
00331   accel_bias_reg[0] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00332   readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]);
00333   accel_bias_reg[1] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00334   readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
00335   accel_bias_reg[2] = (int16_t) ((int16_t)data[0] << 8) | data[1];
00336   
00337   uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers
00338   uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis
00339   
00340   for(ii = 0; ii < 3; ii++) {
00341     if(accel_bias_reg[ii] & mask) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit
00342   }
00343 
00344   // Construct total accelerometer bias, including calculated average accelerometer bias from above
00345   accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale)
00346   accel_bias_reg[1] -= (accel_bias[1]/8);
00347   accel_bias_reg[2] -= (accel_bias[2]/8);
00348  
00349   data[0] = (accel_bias_reg[0] >> 8) & 0xFF;
00350   data[1] = (accel_bias_reg[0])      & 0xFF;
00351   data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00352   data[2] = (accel_bias_reg[1] >> 8) & 0xFF;
00353   data[3] = (accel_bias_reg[1])      & 0xFF;
00354   data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00355   data[4] = (accel_bias_reg[2] >> 8) & 0xFF;
00356   data[5] = (accel_bias_reg[2])      & 0xFF;
00357   data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers
00358 
00359 // Apparently this is not working for the acceleration biases in the MPU-9250
00360 // Are we handling the temperature correction bit properly?
00361 // Push accelerometer biases to hardware registers
00362 /*  writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]);
00363   writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]);
00364   writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]);
00365   writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]);
00366   writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]);
00367   writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);
00368 */
00369 // Output scaled accelerometer biases for manual subtraction in the main program
00370    dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; 
00371    dest2[1] = (float)accel_bias[1]/(float)accelsensitivity;
00372    dest2[2] = (float)accel_bias[2]/(float)accelsensitivity;
00373 }
00374 
00375 
00376 // Accelerometer and gyroscope self test; check calibration wrt factory settings
00377 void MPU9250::MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass
00378 {
00379    uint8_t rawData[6] = {0, 0, 0, 0, 0, 0};
00380    uint8_t selfTest[6];
00381    int16_t gAvg[3], aAvg[3], aSTAvg[3], gSTAvg[3];
00382    float factoryTrim[6];
00383    uint8_t FS = 0;
00384    
00385   writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz
00386   writeByte(MPU9250_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz
00387   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 1<<FS); // Set full scale range for the gyro to 250 dps
00388   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz
00389   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 1<<FS); // Set full scale range for the accelerometer to 2 g
00390 
00391   for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer
00392   
00393   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00394   aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00395   aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00396   aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00397   
00398     readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00399   gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00400   gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00401   gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00402   }
00403   
00404   for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average current readings
00405   aAvg[ii] /= 200;
00406   gAvg[ii] /= 200;
00407   }
00408   
00409 // Configure the accelerometer for self-test
00410    writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g
00411    writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s
00412    wait_ms(25); // Delay a while to let the device stabilize
00413 
00414   for( int ii = 0; ii < 200; ii++) { // get average self-test values of gyro and acclerometer
00415   
00416   readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
00417   aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00418   aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00419   aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00420   
00421     readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
00422   gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
00423   gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
00424   gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
00425   }
00426   
00427   for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average self-test readings
00428   aSTAvg[ii] /= 200;
00429   gSTAvg[ii] /= 200;
00430   }
00431   
00432  // Configure the gyro and accelerometer for normal operation
00433    writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00);
00434    writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);
00435    wait_ms(25); // Delay a while to let the device stabilize
00436    
00437    // Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg
00438    selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results
00439    selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results
00440    selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results
00441    selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results
00442    selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results
00443    selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results
00444 
00445   // Retrieve factory self-test value from self-test code reads
00446    factoryTrim[0] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation
00447    factoryTrim[1] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation
00448    factoryTrim[2] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation
00449    factoryTrim[3] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation
00450    factoryTrim[4] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation
00451    factoryTrim[5] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation
00452  
00453  // Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response
00454  // To get percent, must multiply by 100
00455    for (int i = 0; i < 3; i++) {
00456      destination[i] = 100.0*((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i]; // Report percent differences
00457      destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3]; // Report percent differences
00458    }
00459    
00460 }