Matthias Grob
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FlyBed2
My fully self designed first stable working Quadrocopter Software.
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MPU9250.cpp
00001 #include "MPU9250.h" 00002 00003 MPU9250::MPU9250(PinName MOSI, PinName MISO, PinName SCLK, PinName CS) : spi(MOSI, MISO, SCLK), cs(CS) { 00004 deselect(); // chip must be deselected first 00005 spi.format(8,0); // setup the spi for standard 8 bit data and SPI-Mode 0 00006 spi.frequency(5e6); // with a 5MHz clock rate 00007 00008 /* 00009 last 3 Bits of|Accelerometer(Fs=1kHz) |Gyroscope 00010 MPU9250_CONFIG|Bandwidth(Hz)|Delay(ms)|Bandwidth(Hz)|Delay(ms)|Fs(kHz) 00011 ------------------------------------------------------------------------- 00012 0 |260 |0 |256 |0.98 |8 00013 1 |184 |2.0 |188 |1.9 |1 00014 2 |94 |3.0 |98 |2.8 |1 00015 3 |44 |4.9 |42 |4.8 |1 00016 4 |21 |8.5 |20 |8.3 |1 00017 5 |10 |13.8 |10 |13.4 |1 00018 6 |5 |19.0 |5 |18.6 |1 00019 */ 00020 writeRegister8(MPU9250_CONFIG, 0x06); 00021 writeRegister8(MPU9250_GYRO_CONFIG, 0x18); // scales gyros range to +-2000dps 00022 writeRegister8(MPU9250_ACCEL_CONFIG, 0x08); // scales accelerometers range to +-4g 00023 } 00024 00025 uint8_t MPU9250::getWhoami() { 00026 return readRegister8(MPU9250_WHO_AM_I); 00027 } 00028 00029 float MPU9250::getTemperature() { 00030 int16_t data = readRegister16(MPU9250_TEMP_OUT_H); 00031 return ((data - 21) / 333.87) + 21; // formula from register map p.33 00032 } 00033 00034 void MPU9250::readGyro() { 00035 int16_t rawGyro[3]; 00036 readRegister48(MPU9250_GYRO_XOUT_H, rawGyro); 00037 00038 int16_t offsetGyro[3] = {-31, -15, -11}; // TODO: make better calibration 00039 00040 for (int i = 0; i < 3; i++) 00041 Gyro[i] = (rawGyro[i] - offsetGyro[i])*0.07; // subtract offset from calibration and multiply unit factor to get degree per second (datasheet p.10) 00042 } 00043 00044 void MPU9250::readAcc() { 00045 int16_t rawAcc[3]; 00046 readRegister48(MPU9250_ACCEL_XOUT_H, rawAcc); 00047 00048 int16_t offsetAcc[3] = {-120, -48, -438}; // TODO: make better calibration 00049 00050 for (int i = 0; i < 3; i++) 00051 Acc[i] = (rawAcc[i] - offsetAcc[i])/8192.0; // TODO: didn't care about units because IMU-algorithm just uses vector direction 00052 } 00053 00054 // PRIVATE Methods ------------------------------------------------------------------------------------ 00055 00056 00057 // SPI Interface -------------------------------------------------------------------------------------- 00058 uint8_t MPU9250::readRegister8(uint8_t reg) { 00059 uint8_t result; 00060 readRegister(reg, &result, 1); 00061 return result; 00062 } 00063 00064 uint16_t MPU9250::readRegister16(uint8_t reg) { 00065 uint8_t result[2]; 00066 readRegister(reg, result, 2); 00067 return result[0]<<8 | result[1]; // join 8-Bit pieces to 16-bit short integer 00068 } 00069 00070 void MPU9250::readRegister48(uint8_t reg, int16_t *buffer) { 00071 uint8_t result[6]; 00072 readRegister(reg, result, 6); 00073 buffer[0] = (int16_t) (result[0] << 8 | result[1]); // join 8-Bit pieces to 16-bit short integers 00074 buffer[1] = (int16_t) (result[2] << 8 | result[3]); 00075 buffer[2] = (int16_t) (result[4] << 8 | result[5]); 00076 } 00077 00078 void MPU9250::writeRegister8(uint8_t reg, uint8_t buffer) { 00079 writeRegister(reg, &buffer, 1); 00080 } 00081 00082 void MPU9250::readRegister(uint8_t reg, uint8_t *buffer, int length) { 00083 select(); 00084 spi.write(reg | 0x80); // send the register address we want to read and the read flag 00085 for(int i=0; i<length; i++) // get data 00086 buffer[i] = spi.write(0x00); 00087 deselect(); 00088 } 00089 00090 void MPU9250::writeRegister(uint8_t reg, uint8_t *buffer, int length) { 00091 select(); 00092 spi.write(reg & ~0x80); // send the register address we want to write and the write flag 00093 for(int i=0; i<length; i++) // put data 00094 spi.write(buffer[i]); 00095 deselect(); 00096 } 00097 00098 void MPU9250::select() { cs = 0; } // set Cable Select pin low to start SPI transaction 00099 void MPU9250::deselect() { cs = 1; } // set Cable Select pin high to stop SPI transaction
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