Diff: source/MPU9250.cpp

Revision:

2:1957a4985d6e

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/MPU9250.cpp	Sun Oct 28 13:45:26 2018 +0000
@@ -0,0 +1,460 @@
+#include "MPU9250.h"
+
+#define Kp 2.0f * 5.0f // these are the free parameters in the Mahony filter and fusion scheme, Kp for proportional feedback, Ki for integral
+#define Ki 0.0f
+
+//******************************************************************************
+MPU9250::MPU9250(PinName sda, PinName scl)
+{
+    i2c_ = new I2C(sda, scl);
+    i2c_->frequency(400000);
+}
+
+//******************************************************************************
+MPU9250::MPU9250(I2C *i2c):i2c_(i2c){}
+
+//******************************************************************************
+MPU9250::~MPU9250()
+{    
+   delete i2c_;
+}
+
+void MPU9250::writeByte(uint8_t address, uint8_t subAddress, uint8_t data)
+{
+   char data_write[2];
+   data_write[0] = subAddress;
+   data_write[1] = data;
+   i2c_->write(address, data_write, 2, 0);
+}
+
+char MPU9250::readByte(uint8_t address, uint8_t subAddress)
+{
+    char data[1]; // `data` will store the register data     
+    char data_write[1];
+    data_write[0] = subAddress;
+    i2c_->write(address, data_write, 1, 1); // no stop
+    i2c_->read(address, data, 1, 0); 
+    return data[0]; 
+}
+
+void MPU9250::readBytes(uint8_t address, uint8_t subAddress, uint8_t count, uint8_t * dest)
+{     
+    char data[14];
+    char data_write[1];
+    data_write[0] = subAddress;
+    i2c_->write(address, data_write, 1, 1); // no stop
+    i2c_->read(address, data, count, 0); 
+    for(int ii = 0; ii < count; ii++) {
+     dest[ii] = data[ii];
+    }
+} 
+
+void MPU9250::getMres() {
+  switch (Mscale)
+  {
+    // Possible magnetometer scales (and their register bit settings) are:
+    // 14 bit resolution (0) and 16 bit resolution (1)
+    case MFS_14BITS:
+          mRes = 10.0*4219.0/8190.0; // Proper scale to return milliGauss
+          break;
+    case MFS_16BITS:
+          mRes = 10.0*4219.0/32760.0; // Proper scale to return milliGauss
+          break;
+  }
+}
+
+
+void MPU9250::getGres() {
+  switch (Gscale)
+  {
+    // Possible gyro scales (and their register bit settings) are:
+    // 250 DPS (00), 500 DPS (01), 1000 DPS (10), and 2000 DPS  (11). 
+        // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
+    case GFS_250DPS:
+          gRes = 250.0/32768.0;
+          break;
+    case GFS_500DPS:
+          gRes = 500.0/32768.0;
+          break;
+    case GFS_1000DPS:
+          gRes = 1000.0/32768.0;
+          break;
+    case GFS_2000DPS:
+          gRes = 2000.0/32768.0;
+          break;
+  }
+}
+
+
+void MPU9250::getAres() {
+  switch (Ascale)
+  {
+    // Possible accelerometer scales (and their register bit settings) are:
+    // 2 Gs (00), 4 Gs (01), 8 Gs (10), and 16 Gs  (11). 
+        // Here's a bit of an algorith to calculate DPS/(ADC tick) based on that 2-bit value:
+    case AFS_2G:
+          aRes = 2.0/32768.0;
+          break;
+    case AFS_4G:
+          aRes = 4.0/32768.0;
+          break;
+    case AFS_8G:
+          aRes = 8.0/32768.0;
+          break;
+    case AFS_16G:
+          aRes = 16.0/32768.0;
+          break;
+  }
+}
+
+
+void MPU9250::readAccelData(int16_t * destination)
+{
+  uint8_t rawData[6];  // x/y/z accel register data stored here
+  readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers into data array
+  destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
+  destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
+  destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
+}
+
+void MPU9250::readGyroData(int16_t * destination)
+{
+  uint8_t rawData[6];  // x/y/z gyro register data stored here
+  readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]);  // Read the six raw data registers sequentially into data array
+  destination[0] = (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ;  // Turn the MSB and LSB into a signed 16-bit value
+  destination[1] = (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;  
+  destination[2] = (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ; 
+}
+
+void MPU9250::readMagData(int16_t * destination)
+{
+  uint8_t rawData[7];  // x/y/z gyro register data, ST2 register stored here, must read ST2 at end of data acquisition
+  if(readByte(AK8963_ADDRESS, AK8963_ST1) & 0x01) { // wait for magnetometer data ready bit to be set
+  readBytes(AK8963_ADDRESS, AK8963_XOUT_L, 7, &rawData[0]);  // Read the six raw data and ST2 registers sequentially into data array
+  uint8_t c = rawData[6]; // End data read by reading ST2 register
+    if(!(c & 0x08)) { // Check if magnetic sensor overflow set, if not then report data
+    destination[0] = (int16_t)(((int16_t)rawData[1] << 8) | rawData[0]);  // Turn the MSB and LSB into a signed 16-bit value
+    destination[1] = (int16_t)(((int16_t)rawData[3] << 8) | rawData[2]) ;  // Data stored as little Endian
+    destination[2] = (int16_t)(((int16_t)rawData[5] << 8) | rawData[4]) ; 
+   }
+  }
+}
+
+int16_t MPU9250::readTempData()
+{
+  uint8_t rawData[2];  // x/y/z gyro register data stored here
+  readBytes(MPU9250_ADDRESS, TEMP_OUT_H, 2, &rawData[0]);  // Read the two raw data registers sequentially into data array 
+  return (int16_t)(((int16_t)rawData[0]) << 8 | rawData[1]) ;  // Turn the MSB and LSB into a 16-bit value
+}
+
+
+void MPU9250::resetMPU9250() {
+  // reset device
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
+  wait(0.1);
+  }
+  
+void MPU9250::initAK8963(float * destination)
+{
+  // First extract the factory calibration for each magnetometer axis
+  uint8_t rawData[3];  // x/y/z gyro calibration data stored here
+  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
+  wait(0.01);
+  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x0F); // Enter Fuse ROM access mode
+  wait(0.01);
+  readBytes(AK8963_ADDRESS, AK8963_ASAX, 3, &rawData[0]);  // Read the x-, y-, and z-axis calibration values
+  destination[0] =  (float)(rawData[0] - 128)/256.0f + 1.0f;   // Return x-axis sensitivity adjustment values, etc.
+  destination[1] =  (float)(rawData[1] - 128)/256.0f + 1.0f;  
+  destination[2] =  (float)(rawData[2] - 128)/256.0f + 1.0f; 
+  writeByte(AK8963_ADDRESS, AK8963_CNTL, 0x00); // Power down magnetometer  
+  wait(0.01);
+  // Configure the magnetometer for continuous read and highest resolution
+  // set Mscale bit 4 to 1 (0) to enable 16 (14) bit resolution in CNTL register,
+  // and enable continuous mode data acquisition Mmode (bits [3:0]), 0010 for 8 Hz and 0110 for 100 Hz sample rates
+  writeByte(AK8963_ADDRESS, AK8963_CNTL, Mscale << 4 | Mmode); // Set magnetometer data resolution and sample ODR
+  wait(0.01);
+}
+
+
+void MPU9250::initMPU9250()
+{  
+ // Initialize MPU9250 device
+ // wake up device
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00); // Clear sleep mode bit (6), enable all sensors 
+  wait(0.1); // Delay 100 ms for PLL to get established on x-axis gyro; should check for PLL ready interrupt  
+
+ // get stable time source
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  // Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
+
+ // Configure Gyro and Accelerometer
+ // Disable FSYNC and set accelerometer and gyro bandwidth to 44 and 42 Hz, respectively; 
+ // DLPF_CFG = bits 2:0 = 010; this sets the sample rate at 1 kHz for both
+ // Maximum delay is 4.9 ms which is just over a 200 Hz maximum rate
+  writeByte(MPU9250_ADDRESS, CONFIG, 0x03);  
+ 
+ // Set sample rate = gyroscope output rate/(1 + SMPLRT_DIV)
+  writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x04);  // Use a 200 Hz rate; the same rate set in CONFIG above
+ 
+ // Set gyroscope full scale range
+ // Range selects FS_SEL and AFS_SEL are 0 - 3, so 2-bit values are left-shifted into positions 4:3
+  uint8_t c =  readByte(MPU9250_ADDRESS, GYRO_CONFIG);
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0xE0); // Clear self-test bits [7:5] 
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, c | Gscale << 3); // Set full scale range for the gyro
+   
+ // Set accelerometer configuration
+  c =  readByte(MPU9250_ADDRESS, ACCEL_CONFIG);
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0xE0); // Clear self-test bits [7:5] 
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c & ~0x18); // Clear AFS bits [4:3]
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, c | Ascale << 3); // Set full scale range for the accelerometer 
+
+ // Set accelerometer sample rate configuration
+ // It is possible to get a 4 kHz sample rate from the accelerometer by choosing 1 for
+ // accel_fchoice_b bit [3]; in this case the bandwidth is 1.13 kHz
+  c = readByte(MPU9250_ADDRESS, ACCEL_CONFIG2);
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c & ~0x0F); // Clear accel_fchoice_b (bit 3) and A_DLPFG (bits [2:0])  
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, c | 0x03); // Set accelerometer rate to 1 kHz and bandwidth to 41 Hz
+
+ // The accelerometer, gyro, and thermometer are set to 1 kHz sample rates, 
+ // but all these rates are further reduced by a factor of 5 to 200 Hz because of the SMPLRT_DIV setting
+
+  // Configure Interrupts and Bypass Enable
+  // Set interrupt pin active high, push-pull, and clear on read of INT_STATUS, enable I2C_BYPASS_EN so additional chips 
+  // can join the I2C bus and all can be controlled by the Arduino as master
+   writeByte(MPU9250_ADDRESS, INT_PIN_CFG, 0x22);    
+   writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x01);  // Enable data ready (bit 0) interrupt
+}
+
+// Function which accumulates gyro and accelerometer data after device initialization. It calculates the average
+// of the at-rest readings and then loads the resulting offsets into accelerometer and gyro bias registers.
+void MPU9250::calibrateMPU9250(float * dest1, float * dest2)
+{  
+  uint8_t data[12]; // data array to hold accelerometer and gyro x, y, z, data
+  uint16_t ii, packet_count, fifo_count;
+  int32_t gyro_bias[3] = {0, 0, 0}, accel_bias[3] = {0, 0, 0};
+  
+// reset device, reset all registers, clear gyro and accelerometer bias registers
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x80); // Write a one to bit 7 reset bit; toggle reset device
+  wait(0.1);  
+   
+// get stable time source
+// Set clock source to be PLL with x-axis gyroscope reference, bits 2:0 = 001
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x01);  
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_2, 0x00); 
+  wait(0.2);
+  
+// Configure device for bias calculation
+  writeByte(MPU9250_ADDRESS, INT_ENABLE, 0x00);   // Disable all interrupts
+  writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);      // Disable FIFO
+  writeByte(MPU9250_ADDRESS, PWR_MGMT_1, 0x00);   // Turn on internal clock source
+  writeByte(MPU9250_ADDRESS, I2C_MST_CTRL, 0x00); // Disable I2C master
+  writeByte(MPU9250_ADDRESS, USER_CTRL, 0x00);    // Disable FIFO and I2C master modes
+  writeByte(MPU9250_ADDRESS, USER_CTRL, 0x0C);    // Reset FIFO and DMP
+  wait(0.015);
+  
+// Configure MPU9250 gyro and accelerometer for bias calculation
+  writeByte(MPU9250_ADDRESS, CONFIG, 0x01);      // Set low-pass filter to 188 Hz
+  writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00);  // Set sample rate to 1 kHz
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);  // Set gyro full-scale to 250 degrees per second, maximum sensitivity
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00); // Set accelerometer full-scale to 2 g, maximum sensitivity
+ 
+  uint16_t  gyrosensitivity  = 131;   // = 131 LSB/degrees/sec
+  uint16_t  accelsensitivity = 16384;  // = 16384 LSB/g
+
+// Configure FIFO to capture accelerometer and gyro data for bias calculation
+  writeByte(MPU9250_ADDRESS, USER_CTRL, 0x40);   // Enable FIFO  
+  writeByte(MPU9250_ADDRESS, FIFO_EN, 0x78);     // Enable gyro and accelerometer sensors for FIFO (max size 512 bytes in MPU-9250)
+  wait(0.04); // accumulate 40 samples in 80 milliseconds = 480 bytes
+
+// At end of sample accumulation, turn off FIFO sensor read
+  writeByte(MPU9250_ADDRESS, FIFO_EN, 0x00);        // Disable gyro and accelerometer sensors for FIFO
+  readBytes(MPU9250_ADDRESS, FIFO_COUNTH, 2, &data[0]); // read FIFO sample count
+  fifo_count = ((uint16_t)data[0] << 8) | data[1];
+  packet_count = fifo_count/12;// How many sets of full gyro and accelerometer data for averaging
+
+  for (ii = 0; ii < packet_count; ii++) {
+    int16_t accel_temp[3] = {0, 0, 0}, gyro_temp[3] = {0, 0, 0};
+    readBytes(MPU9250_ADDRESS, FIFO_R_W, 12, &data[0]); // read data for averaging
+    accel_temp[0] = (int16_t) (((int16_t)data[0] << 8) | data[1]  ) ;  // Form signed 16-bit integer for each sample in FIFO
+    accel_temp[1] = (int16_t) (((int16_t)data[2] << 8) | data[3]  ) ;
+    accel_temp[2] = (int16_t) (((int16_t)data[4] << 8) | data[5]  ) ;    
+    gyro_temp[0]  = (int16_t) (((int16_t)data[6] << 8) | data[7]  ) ;
+    gyro_temp[1]  = (int16_t) (((int16_t)data[8] << 8) | data[9]  ) ;
+    gyro_temp[2]  = (int16_t) (((int16_t)data[10] << 8) | data[11]) ;
+    
+    accel_bias[0] += (int32_t) accel_temp[0]; // Sum individual signed 16-bit biases to get accumulated signed 32-bit biases
+    accel_bias[1] += (int32_t) accel_temp[1];
+    accel_bias[2] += (int32_t) accel_temp[2];
+    gyro_bias[0]  += (int32_t) gyro_temp[0];
+    gyro_bias[1]  += (int32_t) gyro_temp[1];
+    gyro_bias[2]  += (int32_t) gyro_temp[2];
+            
+}
+    accel_bias[0] /= (int32_t) packet_count; // Normalize sums to get average count biases
+    accel_bias[1] /= (int32_t) packet_count;
+    accel_bias[2] /= (int32_t) packet_count;
+    gyro_bias[0]  /= (int32_t) packet_count;
+    gyro_bias[1]  /= (int32_t) packet_count;
+    gyro_bias[2]  /= (int32_t) packet_count;
+    
+  if(accel_bias[2] > 0L) {accel_bias[2] -= (int32_t) accelsensitivity;}  // Remove gravity from the z-axis accelerometer bias calculation
+  else {accel_bias[2] += (int32_t) accelsensitivity;}
+ 
+// Construct the gyro biases for push to the hardware gyro bias registers, which are reset to zero upon device startup
+  data[0] = (-gyro_bias[0]/4  >> 8) & 0xFF; // Divide by 4 to get 32.9 LSB per deg/s to conform to expected bias input format
+  data[1] = (-gyro_bias[0]/4)       & 0xFF; // Biases are additive, so change sign on calculated average gyro biases
+  data[2] = (-gyro_bias[1]/4  >> 8) & 0xFF;
+  data[3] = (-gyro_bias[1]/4)       & 0xFF;
+  data[4] = (-gyro_bias[2]/4  >> 8) & 0xFF;
+  data[5] = (-gyro_bias[2]/4)       & 0xFF;
+
+/// Push gyro biases to hardware registers
+/*  writeByte(MPU9250_ADDRESS, XG_OFFSET_H, data[0]);
+  writeByte(MPU9250_ADDRESS, XG_OFFSET_L, data[1]);
+  writeByte(MPU9250_ADDRESS, YG_OFFSET_H, data[2]);
+  writeByte(MPU9250_ADDRESS, YG_OFFSET_L, data[3]);
+  writeByte(MPU9250_ADDRESS, ZG_OFFSET_H, data[4]);
+  writeByte(MPU9250_ADDRESS, ZG_OFFSET_L, data[5]);
+*/
+  dest1[0] = (float) gyro_bias[0]/(float) gyrosensitivity; // construct gyro bias in deg/s for later manual subtraction
+  dest1[1] = (float) gyro_bias[1]/(float) gyrosensitivity;
+  dest1[2] = (float) gyro_bias[2]/(float) gyrosensitivity;
+
+// Construct the accelerometer biases for push to the hardware accelerometer bias registers. These registers contain
+// factory trim values which must be added to the calculated accelerometer biases; on boot up these registers will hold
+// non-zero values. In addition, bit 0 of the lower byte must be preserved since it is used for temperature
+// compensation calculations. Accelerometer bias registers expect bias input as 2048 LSB per g, so that
+// the accelerometer biases calculated above must be divided by 8.
+
+  int32_t accel_bias_reg[3] = {0, 0, 0}; // A place to hold the factory accelerometer trim biases
+  readBytes(MPU9250_ADDRESS, XA_OFFSET_H, 2, &data[0]); // Read factory accelerometer trim values
+  accel_bias_reg[0] = (int16_t) ((int16_t)data[0] << 8) | data[1];
+  readBytes(MPU9250_ADDRESS, YA_OFFSET_H, 2, &data[0]);
+  accel_bias_reg[1] = (int16_t) ((int16_t)data[0] << 8) | data[1];
+  readBytes(MPU9250_ADDRESS, ZA_OFFSET_H, 2, &data[0]);
+  accel_bias_reg[2] = (int16_t) ((int16_t)data[0] << 8) | data[1];
+  
+  uint32_t mask = 1uL; // Define mask for temperature compensation bit 0 of lower byte of accelerometer bias registers
+  uint8_t mask_bit[3] = {0, 0, 0}; // Define array to hold mask bit for each accelerometer bias axis
+  
+  for(ii = 0; ii < 3; ii++) {
+    if(accel_bias_reg[ii] & mask) mask_bit[ii] = 0x01; // If temperature compensation bit is set, record that fact in mask_bit
+  }
+
+  // Construct total accelerometer bias, including calculated average accelerometer bias from above
+  accel_bias_reg[0] -= (accel_bias[0]/8); // Subtract calculated averaged accelerometer bias scaled to 2048 LSB/g (16 g full scale)
+  accel_bias_reg[1] -= (accel_bias[1]/8);
+  accel_bias_reg[2] -= (accel_bias[2]/8);
+ 
+  data[0] = (accel_bias_reg[0] >> 8) & 0xFF;
+  data[1] = (accel_bias_reg[0])      & 0xFF;
+  data[1] = data[1] | mask_bit[0]; // preserve temperature compensation bit when writing back to accelerometer bias registers
+  data[2] = (accel_bias_reg[1] >> 8) & 0xFF;
+  data[3] = (accel_bias_reg[1])      & 0xFF;
+  data[3] = data[3] | mask_bit[1]; // preserve temperature compensation bit when writing back to accelerometer bias registers
+  data[4] = (accel_bias_reg[2] >> 8) & 0xFF;
+  data[5] = (accel_bias_reg[2])      & 0xFF;
+  data[5] = data[5] | mask_bit[2]; // preserve temperature compensation bit when writing back to accelerometer bias registers
+
+// Apparently this is not working for the acceleration biases in the MPU-9250
+// Are we handling the temperature correction bit properly?
+// Push accelerometer biases to hardware registers
+/*  writeByte(MPU9250_ADDRESS, XA_OFFSET_H, data[0]);
+  writeByte(MPU9250_ADDRESS, XA_OFFSET_L, data[1]);
+  writeByte(MPU9250_ADDRESS, YA_OFFSET_H, data[2]);
+  writeByte(MPU9250_ADDRESS, YA_OFFSET_L, data[3]);
+  writeByte(MPU9250_ADDRESS, ZA_OFFSET_H, data[4]);
+  writeByte(MPU9250_ADDRESS, ZA_OFFSET_L, data[5]);
+*/
+// Output scaled accelerometer biases for manual subtraction in the main program
+   dest2[0] = (float)accel_bias[0]/(float)accelsensitivity; 
+   dest2[1] = (float)accel_bias[1]/(float)accelsensitivity;
+   dest2[2] = (float)accel_bias[2]/(float)accelsensitivity;
+}
+
+
+// Accelerometer and gyroscope self test; check calibration wrt factory settings
+void MPU9250::MPU9250SelfTest(float * destination) // Should return percent deviation from factory trim values, +/- 14 or less deviation is a pass
+{
+   uint8_t rawData[6] = {0, 0, 0, 0, 0, 0};
+   uint8_t selfTest[6];
+   int16_t gAvg[3], aAvg[3], aSTAvg[3], gSTAvg[3];
+   float factoryTrim[6];
+   uint8_t FS = 0;
+   
+  writeByte(MPU9250_ADDRESS, SMPLRT_DIV, 0x00); // Set gyro sample rate to 1 kHz
+  writeByte(MPU9250_ADDRESS, CONFIG, 0x02); // Set gyro sample rate to 1 kHz and DLPF to 92 Hz
+  writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 1<<FS); // Set full scale range for the gyro to 250 dps
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG2, 0x02); // Set accelerometer rate to 1 kHz and bandwidth to 92 Hz
+  writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 1<<FS); // Set full scale range for the accelerometer to 2 g
+
+  for( int ii = 0; ii < 200; ii++) { // get average current values of gyro and acclerometer
+  
+  readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
+  aAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
+  aAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
+  aAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
+  
+    readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
+  gAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
+  gAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
+  gAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
+  }
+  
+  for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average current readings
+  aAvg[ii] /= 200;
+  gAvg[ii] /= 200;
+  }
+  
+// Configure the accelerometer for self-test
+   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0xE0); // Enable self test on all three axes and set accelerometer range to +/- 2 g
+   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0xE0); // Enable self test on all three axes and set gyro range to +/- 250 degrees/s
+   wait_ms(25); // Delay a while to let the device stabilize
+
+  for( int ii = 0; ii < 200; ii++) { // get average self-test values of gyro and acclerometer
+  
+  readBytes(MPU9250_ADDRESS, ACCEL_XOUT_H, 6, &rawData[0]); // Read the six raw data registers into data array
+  aSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
+  aSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
+  aSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
+  
+    readBytes(MPU9250_ADDRESS, GYRO_XOUT_H, 6, &rawData[0]); // Read the six raw data registers sequentially into data array
+  gSTAvg[0] += (int16_t)(((int16_t)rawData[0] << 8) | rawData[1]) ; // Turn the MSB and LSB into a signed 16-bit value
+  gSTAvg[1] += (int16_t)(((int16_t)rawData[2] << 8) | rawData[3]) ;
+  gSTAvg[2] += (int16_t)(((int16_t)rawData[4] << 8) | rawData[5]) ;
+  }
+  
+  for (int ii =0; ii < 3; ii++) { // Get average of 200 values and store as average self-test readings
+  aSTAvg[ii] /= 200;
+  gSTAvg[ii] /= 200;
+  }
+  
+ // Configure the gyro and accelerometer for normal operation
+   writeByte(MPU9250_ADDRESS, ACCEL_CONFIG, 0x00);
+   writeByte(MPU9250_ADDRESS, GYRO_CONFIG, 0x00);
+   wait_ms(25); // Delay a while to let the device stabilize
+   
+   // Retrieve accelerometer and gyro factory Self-Test Code from USR_Reg
+   selfTest[0] = readByte(MPU9250_ADDRESS, SELF_TEST_X_ACCEL); // X-axis accel self-test results
+   selfTest[1] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_ACCEL); // Y-axis accel self-test results
+   selfTest[2] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_ACCEL); // Z-axis accel self-test results
+   selfTest[3] = readByte(MPU9250_ADDRESS, SELF_TEST_X_GYRO); // X-axis gyro self-test results
+   selfTest[4] = readByte(MPU9250_ADDRESS, SELF_TEST_Y_GYRO); // Y-axis gyro self-test results
+   selfTest[5] = readByte(MPU9250_ADDRESS, SELF_TEST_Z_GYRO); // Z-axis gyro self-test results
+
+  // Retrieve factory self-test value from self-test code reads
+   factoryTrim[0] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[0] - 1.0) )); // FT[Xa] factory trim calculation
+   factoryTrim[1] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[1] - 1.0) )); // FT[Ya] factory trim calculation
+   factoryTrim[2] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[2] - 1.0) )); // FT[Za] factory trim calculation
+   factoryTrim[3] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[3] - 1.0) )); // FT[Xg] factory trim calculation
+   factoryTrim[4] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[4] - 1.0) )); // FT[Yg] factory trim calculation
+   factoryTrim[5] = (float)(2620/1<<FS)*(pow( 1.01 , ((float)selfTest[5] - 1.0) )); // FT[Zg] factory trim calculation
+ 
+ // Report results as a ratio of (STR - FT)/FT; the change from Factory Trim of the Self-Test Response
+ // To get percent, must multiply by 100
+   for (int i = 0; i < 3; i++) {
+     destination[i] = 100.0*((float)(aSTAvg[i] - aAvg[i]))/factoryTrim[i]; // Report percent differences
+     destination[i+3] = 100.0*((float)(gSTAvg[i] - gAvg[i]))/factoryTrim[i+3]; // Report percent differences
+   }
+   
+}
\ No newline at end of file