MPU6050.cpp

00001 #include "MPU6050.h"
00002 
00003 MPU6050::MPU6050(PinName sda, PinName scl) : I2C_Sensor(sda, scl, MPU6050_I2C_ADDRESS)
00004 {
00005     // Turns on the MPU6050's gyro and initializes it
00006     // register datasheet: http://www.invensense.com/mems/gyro/documents/RM-MPU-6000A.pdf
00007     writeRegister(MPU6050_RA_PWR_MGMT_1, 0x01);         // wake up from sleep and chooses Gyro X-Axis as Clock source (stadard sleeping and with inacurate clock is 0x40)
00008     writeRegister(MPU6050_RA_CONFIG, 0x03);   
00009     /*
00010     last 3 Bits of   |Accelerometer(Fs=1kHz) |Gyroscope 
00011     MPU6050_RA_CONFIG|Bandwidth(Hz)|Delay(ms)|Bandwidth(Hz)|Delay(ms)|Fs(kHz)
00012     ------------------------------------------------------------------------- 
00013     0                |260          |0        |256          |0.98     |8 
00014     1                |184          |2.0      |188          |1.9      |1 
00015     2                |94           |3.0      |98           |2.8      |1 
00016     3                |44           |4.9      |42           |4.8      |1 
00017     4                |21           |8.5      |20           |8.3      |1 
00018     5                |10           |13.8     |10           |13.4     |1 
00019     6                |5            |19.0     |5            |18.6     |1 
00020     */
00021     writeRegister(MPU6050_RA_GYRO_CONFIG, 0x18);        // scales gyros range to +-2000dps
00022     writeRegister(MPU6050_RA_ACCEL_CONFIG, 0x00);       // scales accelerometers range to +-2g
00023 }
00024 
00025 void MPU6050::read()
00026 {
00027     readraw_gyro();                                          // read raw measurement data
00028     readraw_acc();
00029     
00030     for (int i = 0; i < 3; i++)
00031         data_gyro[i] = (raw_gyro[i] - offset_gyro[i])*0.07; // subtract offset from calibration and multiply unit factor to get degree per second (datasheet p.10)
00032     
00033     for (int i = 0; i < 3; i++)
00034         data_acc[i] = raw_acc[i] - offset_acc[i];           // TODO: didn't care about units because IMU-algorithm just uses vector direction
00035 
00036     // I have to swich coordinates on my board to match the ones of the other sensors (clear this part if you use the raw coordinates of the sensor)
00037     float tmp = 0;
00038     tmp = data_gyro[0];
00039     data_gyro[0] = data_gyro[1];
00040     data_gyro[1] = -tmp;
00041     data_gyro[2] = data_gyro[2];
00042     tmp = data_acc[0];
00043     data_acc[0] = data_acc[1];
00044     data_acc[1] = -tmp;
00045     data_acc[2] = data_acc[2];
00046 }
00047 
00048 int MPU6050::readTemp()
00049 {
00050     char buffer[2];                                     // 8-Bit pieces of temperature data
00051     
00052     readMultiRegister(MPU6050_RA_TEMP_OUT_H, buffer, 2);     // read the sensors register for the temperature
00053     return (short) (buffer[0] << 8 | buffer[1]);
00054 }
00055 
00056 void MPU6050::readraw_gyro()
00057 {
00058     char buffer[6];                                     // 8-Bit pieces of axis data
00059     
00060     if(readMultiRegister(MPU6050_RA_GYRO_XOUT_H | (1 << 7), buffer, 6) != 0) return; // read axis registers using I2C   // TODO: why?!   | (1 << 7)
00061     
00062     raw_gyro[0] = (short) (buffer[0] << 8 | buffer[1]);     // join 8-Bit pieces to 16-bit short integers
00063     raw_gyro[1] = (short) (buffer[2] << 8 | buffer[3]);
00064     raw_gyro[2] = (short) (buffer[4] << 8 | buffer[5]);
00065 }
00066 
00067 void MPU6050::readraw_acc()
00068 {
00069     char buffer[6];                                     // 8-Bit pieces of axis data
00070     
00071     readMultiRegister(MPU6050_RA_ACCEL_XOUT_H | (1 << 7), buffer, 6); // read axis registers using I2C   // TODO: why?!   | (1 << 7)
00072     
00073     raw_acc[0] = (short) (buffer[0] << 8 | buffer[1]);     // join 8-Bit pieces to 16-bit short integers
00074     raw_acc[1] = (short) (buffer[2] << 8 | buffer[3]);
00075     raw_acc[2] = (short) (buffer[4] << 8 | buffer[5]);
00076 }
00077 
00078 void MPU6050::calibrate(int times, float separation_time)
00079 {
00080     // calibrate sensor with an average of count samples (result of calibration stored in offset[])
00081     // Calibrate Gyroscope ----------------------------------
00082     float calib_gyro[3] = {0,0,0};                           // temporary array for the sum of calibration measurement
00083     
00084     for (int i = 0; i < times; i++) {                   // read 'times' times the data in a very short time
00085         readraw_gyro();
00086         for (int j = 0; j < 3; j++)
00087             calib_gyro[j] += raw_gyro[j];
00088         wait(separation_time);
00089     }
00090     
00091     for (int i = 0; i < 3; i++)
00092         offset_gyro[i] = calib_gyro[i]/times;                     // take the average of the calibration measurements
00093     
00094     // Calibrate Accelerometer ------------------------------- 
00095     float calib_acc[3] = {0,0,0};                           // temporary array for the sum of calibration measurement
00096     
00097     for (int i = 0; i < times; i++) {                   // read 'times' times the data in a very short time
00098         readraw_acc();
00099         for (int j = 0; j < 3; j++)
00100             calib_acc[j] += raw_acc[j];
00101         wait(separation_time);
00102     }
00103     
00104     for (int i = 0; i < 2; i++)
00105         offset_acc[i] = calib_acc[i]/times;                     // take the average of the calibration measurements
00106 }