MPU6050作為I2C MASTER讀取HMC5883數據，MPU6050的XDA和XCL分別與HMC5883的SDA和SCL相連。
下面引用MultiWii中配置MPU6050 I2C MASTER的代碼段： //at this stage, the MAG is configured via the original MAG init function in I2C bypass mode
//now we configure MPU as a I2C Master device to handle the MAG via the I2C AUX port (done here for HMC5883)
#if defined(MPU6050_I2C_AUX_MASTER) i2c_writeReg(MPU6050_ADDRESS, 0x6A, 0b00100000); //USER_CTRL -- DMP_EN=0 ; FIFO_EN=0 ;I2C_MST_EN=1 (I2C master mode) ; I2C_IF_DIS=0 ; FIFO_RESET=0 ; I2C_MST_RESET=0 ; SIG_COND_RESET=0
i2c_writeReg(MPU6050_ADDRESS, 0x37, 0x00); //INT_PIN_CFG -- INT_LEVEL=0 ; INT_OPEN=0 ; LATCH_INT_EN=0 ; INT_RD_CLEAR=0 ; FSYNC_INT_LEVEL=0 ; FSYNC_INT_EN=0 ; I2C_BYPASS_EN=0 ; CLKOUT_EN=0
i2c_writeReg(MPU6050_ADDRESS, 0x24, 0x0D); //I2C_MST_CTRL -- MULT_MST_EN=0 ; WAIT_FOR_ES=0 ; SLV_3_FIFO_EN=0 ; I2C_MST_P_NSR=0 ; I2C_MST_CLK=13 (I2C slave speed bus = 400kHz)
i2c_writeReg(MPU6050_ADDRESS, 0x25, 0x80|MAG_ADDRESS);//I2C_SLV0_ADDR -- I2C_SLV4_RW=1 (read operation) ; I2C_SLV4_ADDR=MAG_ADDRESS
i2c_writeReg(MPU6050_ADDRESS, 0x26, MAG_DATA_REGISTER);//I2C_SLV0_REG -- 6 data bytes of MAG are stored in 6 registers. First register address is MAG_DATA_REGISTER i2c_writeReg(MPU6050_ADDRESS, 0x27, 0x86); //I2C_SLV0_CTRL -- I2C_SLV0_EN=1 ; I2C_SLV0_BYTE_SW=0 ; I2C_SLV0_REG_DIS=0 ; I2C_SLV0_GRP=0 ; I2C_SLV0_LEN=3 (3x2 bytes)
#endif
下面是Multiwii中通過MPU6050讀取HMC5883或其他磁感應計的代碼：
//The MAG acquisition function must be replaced because we now talk to the MPU device
#if defined(MPU6050_I2C_AUX_MASTER)
void Device_Mag_getADC()
{
i2c_getSixRawADC(MPU6050_ADDRESS, 0x49); //0x49 is the first memory room for EXT_SENS_DATA
#if defined(HMC5843)
MAG_ORIENTATION( ((rawADC[0]<<8) | rawADC[1]) , ((rawADC[2]<<8) | rawADC[3]) , ((rawADC[4]<<8) | rawADC[5]) );
#endif
#if defined (HMC5883)
MAG_ORIENTATION( ((rawADC[0]<<8) | rawADC[1]) , ((rawADC[4]<<8) | rawADC[5]) , ((rawADC[2]<<8) | rawADC[3]) );
#endif
#if defined (MAG3110)
MAG_ORIENTATION( ((rawADC[0]<<8) | rawADC[1]) , ((rawADC[2]<<8) | rawADC[3]) , ((rawADC[4]<<8) | rawADC[5]) );
#endif
}
#endif
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