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MPU 9150 magnetometer raw data

mcprakash
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mcprakash Newbie

mcprakash

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Hi Jeff

 I am new to using MPU9150. I am using Arduino Mega to read the data. I just ran the code given here http://playground.arduino.cc/Main/MPU-9150 .  I am able to get the raw values of acc and gyros properly. However, the magnetometer data is just almost the same for all three axes. Can you help me out ?? The exact code I am using is given below :

 

#include <Wire.h>
#include <math.h>
// Math Constants
#define PI 3.142

// Address of MPU9150 memory registers
.
#define MPU9150_SELF_TEST_X        0x0D   // R/W
#define MPU9150_SELF_TEST_Y        0x0E   // R/W
#define MPU9150_SELF_TEST_X        0x0F   // R/W
#define MPU9150_SELF_TEST_A        0x10   // R/W
#define MPU9150_SMPLRT_DIV         0x19   // R/W
#define MPU9150_CONFIG             0x1A   // R/W
#define MPU9150_GYRO_CONFIG        0x1B   // R/W
#define MPU9150_ACCEL_CONFIG       0x1C   // R/W
#define MPU9150_FF_THR             0x1D   // R/W
#define MPU9150_FF_DUR             0x1E   // R/W
#define MPU9150_MOT_THR            0x1F   // R/W
#define MPU9150_MOT_DUR            0x20   // R/W
#define MPU9150_ZRMOT_THR          0x21   // R/W
#define MPU9150_ZRMOT_DUR          0x22   // R/W
#define MPU9150_FIFO_EN            0x23   // R/W
#define MPU9150_I2C_MST_CTRL       0x24   // R/W
#define MPU9150_I2C_SLV0_ADDR      0x25   // R/W
#define MPU9150_I2C_SLV0_REG       0x26   // R/W
#define MPU9150_I2C_SLV0_CTRL      0x27   // R/W
#define MPU9150_I2C_SLV1_ADDR      0x28   // R/W
#define MPU9150_I2C_SLV1_REG       0x29   // R/W
#define MPU9150_I2C_SLV1_CTRL      0x2A   // R/W
#define MPU9150_I2C_SLV2_ADDR      0x2B   // R/W
#define MPU9150_I2C_SLV2_REG       0x2C   // R/W
#define MPU9150_I2C_SLV2_CTRL      0x2D   // R/W
#define MPU9150_I2C_SLV3_ADDR      0x2E   // R/W
#define MPU9150_I2C_SLV3_REG       0x2F   // R/W
#define MPU9150_I2C_SLV3_CTRL      0x30   // R/W
#define MPU9150_I2C_SLV4_ADDR      0x31   // R/W
#define MPU9150_I2C_SLV4_REG       0x32   // R/W
#define MPU9150_I2C_SLV4_DO        0x33   // R/W
#define MPU9150_I2C_SLV4_CTRL      0x34   // R/W
#define MPU9150_I2C_SLV4_DI        0x35   // R  
#define MPU9150_I2C_MST_STATUS     0x36   // R
#define MPU9150_INT_PIN_CFG        0x37   // R/W
#define MPU9150_INT_ENABLE         0x38   // R/W
#define MPU9150_INT_STATUS         0x3A   // R  
#define MPU9150_ACCEL_XOUT_H       0x3B   // R  
#define MPU9150_ACCEL_XOUT_L       0x3C   // R  
#define MPU9150_ACCEL_YOUT_H       0x3D   // R  
#define MPU9150_ACCEL_YOUT_L       0x3E   // R  
#define MPU9150_ACCEL_ZOUT_H       0x3F   // R  
#define MPU9150_ACCEL_ZOUT_L       0x40   // R  
#define MPU9150_TEMP_OUT_H         0x41   // R  
#define MPU9150_TEMP_OUT_L         0x42   // R  
#define MPU9150_GYRO_XOUT_H        0x43   // R  
#define MPU9150_GYRO_XOUT_L        0x44   // R  
#define MPU9150_GYRO_YOUT_H        0x45   // R  
#define MPU9150_GYRO_YOUT_L        0x46   // R  
#define MPU9150_GYRO_ZOUT_H        0x47   // R  
#define MPU9150_GYRO_ZOUT_L        0x48   // R  
#define MPU9150_EXT_SENS_DATA_00   0x49   // R  
#define MPU9150_EXT_SENS_DATA_01   0x4A   // R  
#define MPU9150_EXT_SENS_DATA_02   0x4B   // R  
#define MPU9150_EXT_SENS_DATA_03   0x4C   // R  
#define MPU9150_EXT_SENS_DATA_04   0x4D   // R  
#define MPU9150_EXT_SENS_DATA_05   0x4E   // R  
#define MPU9150_EXT_SENS_DATA_06   0x4F   // R  
#define MPU9150_EXT_SENS_DATA_07   0x50   // R  
#define MPU9150_EXT_SENS_DATA_08   0x51   // R  
#define MPU9150_EXT_SENS_DATA_09   0x52   // R  
#define MPU9150_EXT_SENS_DATA_10   0x53   // R  
#define MPU9150_EXT_SENS_DATA_11   0x54   // R  
#define MPU9150_EXT_SENS_DATA_12   0x55   // R  
#define MPU9150_EXT_SENS_DATA_13   0x56   // R  
#define MPU9150_EXT_SENS_DATA_14   0x57   // R  
#define MPU9150_EXT_SENS_DATA_15   0x58   // R  
#define MPU9150_EXT_SENS_DATA_16   0x59   // R  
#define MPU9150_EXT_SENS_DATA_17   0x5A   // R  
#define MPU9150_EXT_SENS_DATA_18   0x5B   // R  
#define MPU9150_EXT_SENS_DATA_19   0x5C   // R
#define MPU9150_EXT_SENS_DATA_20   0x5D   // R  
#define MPU9150_EXT_SENS_DATA_21   0x5E   // R  
#define MPU9150_EXT_SENS_DATA_22   0x5F   // R  
#define MPU9150_EXT_SENS_DATA_23   0x60   // R  
#define MPU9150_MOT_DETECT_STATUS  0x61   // R  
#define MPU9150_I2C_SLV0_DO        0x63   // R/W
#define MPU9150_I2C_SLV1_DO        0x64   // R/W
#define MPU9150_I2C_SLV2_DO        0x65   // R/W
#define MPU9150_I2C_SLV3_DO        0x66   // R/W
#define MPU9150_I2C_MST_DELAY_CTRL 0x67   // R/W
#define MPU9150_SIGNAL_PATH_RESET  0x68   // R/W
#define MPU9150_MOT_DETECT_CTRL    0x69   // R/W
#define MPU9150_USER_CTRL          0x6A   // R/W
#define MPU9150_PWR_MGMT_1         0x6B   // R/W
#define MPU9150_PWR_MGMT_2         0x6C   // R/W
#define MPU9150_FIFO_COUNTH        0x72   // R/W
#define MPU9150_FIFO_COUNTL        0x73   // R/W
#define MPU9150_FIFO_R_W           0x74   // R/W
#define MPU9150_WHO_AM_I           0x75   // R

//MPU9150 Compass
#define MPU9150_CMPS_XOUT_L        0x4A   // R
#define MPU9150_CMPS_XOUT_H        0x4B   // R
#define MPU9150_CMPS_YOUT_L        0x4C   // R
#define MPU9150_CMPS_YOUT_H        0x4D   // R
#define MPU9150_CMPS_ZOUT_L        0x4E   // R
#define MPU9150_CMPS_ZOUT_H        0x4F   // R


// I2C address 0x69 could be 0x68 depends on your wiring.
int MPU9150_I2C_ADDRESS = 0x68;

// Variables to define gyro and accel biases
double gyro_bias[3]={0};
double acc_bias[3]={0};

// Variables where our values can be stored
double cmps[3]={0};
double acc[3]={0};
double gyro[3]={0};

// State Variables
double euler[3]={0};
double pos[3]={0};
double vel[3]={0};

// Time Variables

unsigned long time=0,time_prev=0;




// Start of Main Program
void setup()
{
    // Initialize the Serial Bus for printing data.
    Serial.begin(115200);
        
    // Initialize the 'Wire' class for the I2C-bus.
    Wire.begin();

    // Clear the 'sleep' bit to start the sensor.
    MPU9150_write(MPU9150_PWR_MGMT_1, 0);

    MPU9150_setupCompass();
        
        delay(2000);
}


void loop()
{

    // Temperature

    double dT = ((double)MPU9150_read(MPU9150_TEMP_OUT_L, MPU9150_TEMP_OUT_H) + 12412.0) / 340.0;
        
        // Magnetometer
        int mx=MPU9150_read(MPU9150_CMPS_XOUT_L, MPU9150_CMPS_XOUT_H);
        int my=MPU9150_read(MPU9150_CMPS_YOUT_L, MPU9150_CMPS_YOUT_H);
        int mz=MPU9150_read(MPU9150_CMPS_ZOUT_L, MPU9150_CMPS_ZOUT_H);
        
        // Gyro Rates
        int p= MPU9150_read(MPU9150_GYRO_XOUT_L, MPU9150_GYRO_XOUT_H);
        int q= MPU9150_read(MPU9150_GYRO_YOUT_L, MPU9150_GYRO_YOUT_H);
        int r= MPU9150_read(MPU9150_GYRO_ZOUT_L, MPU9150_GYRO_ZOUT_H);
        
        // Accelerometer
        int ax=MPU9150_read(MPU9150_ACCEL_XOUT_L, MPU9150_ACCEL_XOUT_H);
        int ay=MPU9150_read(MPU9150_ACCEL_YOUT_L, MPU9150_ACCEL_YOUT_H);
        int az=MPU9150_read(MPU9150_ACCEL_ZOUT_L, MPU9150_ACCEL_ZOUT_H);
        
        // Get floating point values
        acc[0]=(double)ax/16384*9.81-acc_bias[0];
        acc[1]=(double)ay/16384*9.81-acc_bias[1];
        acc[2]=(double)az/16384*9.81-acc_bias[2];
        double a[3]={0};
        
        gyro[0]=(double)p/131*PI/180-gyro_bias[0];
        gyro[1]=(double)q/131*PI/180-gyro_bias[1];
        gyro[2]=(double)r/131*PI/180-gyro_bias[2];
        
        cmps[0]=(double)mx*0.3;
        cmps[1]=(double)my*0.3;
        cmps[2]=(double)mz*0.3;
       
        Serial.print("T=");Serial.println(dT);
        Serial.print("ax=");Serial.println(acc[0],4);
        Serial.print("ay=");Serial.println(acc[1],4);
        Serial.print("az=");Serial.println(acc[2],4);
        Serial.print("p=");Serial.println(gyro[0],4);
        Serial.print("q=");Serial.println(gyro[1],4);
        Serial.print("r=");Serial.println(gyro[2],4);
        Serial.print("mx=");Serial.println(cmps[0],4);
        Serial.print("my=");Serial.println(cmps[1],4);
        Serial.print("mz=");Serial.println(cmps[2],4);
       
        Serial.println("%%%%%%%%%% End of Time Step%%%%%%%%%%");
        Serial.println("");
        
    delay(10);
}
 
// Set up Compass only once
void MPU9150_setupCompass(){
    
        int tempAddress = MPU9150_I2C_ADDRESS; //temporarily store mpu9150 i2c address as it will later be modified

    MPU9150_I2C_ADDRESS = 0x0C;      //change Address to Compass    

    MPU9150_write(0x0A, 0x00); //PowerDownMode
    MPU9150_write(0x0A, 0x0F); //SelfTest
    MPU9150_write(0x0A, 0x00); //PowerDownMode

    //MPU9150_I2C_ADDRESS = 0x68;      //change Address to MPU
    MPU9150_I2C_ADDRESS = tempAddress; //new version to revert to original address

    MPU9150_write(0x24, 0x40); //Wait for Data at Slave0
    MPU9150_write(0x25, 0x8C); //Set i2c address at slave0 at 0x0C
    MPU9150_write(0x26, 0x02); //Set where reading at slave 0 starts
    MPU9150_write(0x27, 0x88); //set offset at start reading and enable
    MPU9150_write(0x28, 0x0C); //set i2c address at slv1 at 0x0C
    MPU9150_write(0x29, 0x0A); //Set where reading at slave 1 starts
    MPU9150_write(0x2A, 0x81); //Enable at set length to 1
    MPU9150_write(0x64, 0x01); //overvride register
    MPU9150_write(0x67, 0x03); //set delay rate
    MPU9150_write(0x01, 0x80);

    MPU9150_write(0x34, 0x04); //set i2c slv4 delay
    MPU9150_write(0x64, 0x00); //override register
    MPU9150_write(0x6A, 0x00); //clear usr setting
    MPU9150_write(0x64, 0x01); //override register
    MPU9150_write(0x6A, 0x20); //enable master i2c mode
    MPU9150_write(0x34, 0x13); //disable slv4
}

////////////////////////////////////////////////////////////
///////// I2C functions to get easier all values ///////////
////////////////////////////////////////////////////////////

int MPU9150_read(int addrL, int addrH){
    Wire.beginTransmission(MPU9150_I2C_ADDRESS);
    Wire.write(addrL);
    Wire.endTransmission(false);

    Wire.requestFrom(MPU9150_I2C_ADDRESS, 1, true);
    byte L = Wire.read();

    Wire.beginTransmission(MPU9150_I2C_ADDRESS);
    Wire.write(addrH);
    Wire.endTransmission(false);

    Wire.requestFrom(MPU9150_I2C_ADDRESS, 1, true);
    byte H = Wire.read();

    return (H << 8) + L;
}


int MPU9150_write(int addr, int data){
    Wire.beginTransmission(MPU9150_I2C_ADDRESS);
    Wire.write(addr);
    Wire.write(data);
    Wire.endTransmission(true);

    return 1;
}

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  • 1 month later...
WVCFreelancer Newbie

WVCFreelancer

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Do you ever enable single read mode? You have to do that once before every time you take a reading from the six registers for values (I found, not in between every single register read).

 

My problem at the moment is spastic raw output that sure looks unusable to me, despite that it DOES respond to the way it's oriented or how I move a magnet around the device.

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Smolaie Newbie

Smolaie

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Hi Jeff

 I am new to using MPU9150. I am using Arduino Mega to read the data. I just ran the code given here http://playground.arduino.cc/Main/MPU-9150 .  I am able to get the raw values of acc and gyros properly. However, the magnetometer data is just almost the same for all three axes. Can you help me out ?? The exact code I am using is given below :

 

#include <Wire.h>

#include <math.h>

// Math Constants

#define PI 3.142

// Address of MPU9150 memory registers

.

#define MPU9150_SELF_TEST_X        0x0D   // R/W

#define MPU9150_SELF_TEST_Y        0x0E   // R/W

#define MPU9150_SELF_TEST_X        0x0F   // R/W

#define MPU9150_SELF_TEST_A        0x10   // R/W

#define MPU9150_SMPLRT_DIV         0x19   // R/W

#define MPU9150_CONFIG             0x1A   // R/W

#define MPU9150_GYRO_CONFIG        0x1B   // R/W

#define MPU9150_ACCEL_CONFIG       0x1C   // R/W

#define MPU9150_FF_THR             0x1D   // R/W

#define MPU9150_FF_DUR             0x1E   // R/W

#define MPU9150_MOT_THR            0x1F   // R/W

#define MPU9150_MOT_DUR            0x20   // R/W

#define MPU9150_ZRMOT_THR          0x21   // R/W

#define MPU9150_ZRMOT_DUR          0x22   // R/W

#define MPU9150_FIFO_EN            0x23   // R/W

#define MPU9150_I2C_MST_CTRL       0x24   // R/W

#define MPU9150_I2C_SLV0_ADDR      0x25   // R/W

#define MPU9150_I2C_SLV0_REG       0x26   // R/W

#define MPU9150_I2C_SLV0_CTRL      0x27   // R/W

#define MPU9150_I2C_SLV1_ADDR      0x28   // R/W

#define MPU9150_I2C_SLV1_REG       0x29   // R/W

#define MPU9150_I2C_SLV1_CTRL      0x2A   // R/W

#define MPU9150_I2C_SLV2_ADDR      0x2B   // R/W

#define MPU9150_I2C_SLV2_REG       0x2C   // R/W

#define MPU9150_I2C_SLV2_CTRL      0x2D   // R/W

#define MPU9150_I2C_SLV3_ADDR      0x2E   // R/W

#define MPU9150_I2C_SLV3_REG       0x2F   // R/W

#define MPU9150_I2C_SLV3_CTRL      0x30   // R/W

#define MPU9150_I2C_SLV4_ADDR      0x31   // R/W

#define MPU9150_I2C_SLV4_REG       0x32   // R/W

#define MPU9150_I2C_SLV4_DO        0x33   // R/W

#define MPU9150_I2C_SLV4_CTRL      0x34   // R/W

#define MPU9150_I2C_SLV4_DI        0x35   // R  

#define MPU9150_I2C_MST_STATUS     0x36   // R

#define MPU9150_INT_PIN_CFG        0x37   // R/W

#define MPU9150_INT_ENABLE         0x38   // R/W

#define MPU9150_INT_STATUS         0x3A   // R  

#define MPU9150_ACCEL_XOUT_H       0x3B   // R  

#define MPU9150_ACCEL_XOUT_L       0x3C   // R  

#define MPU9150_ACCEL_YOUT_H       0x3D   // R  

#define MPU9150_ACCEL_YOUT_L       0x3E   // R  

#define MPU9150_ACCEL_ZOUT_H       0x3F   // R  

#define MPU9150_ACCEL_ZOUT_L       0x40   // R  

#define MPU9150_TEMP_OUT_H         0x41   // R  

#define MPU9150_TEMP_OUT_L         0x42   // R  

#define MPU9150_GYRO_XOUT_H        0x43   // R  

#define MPU9150_GYRO_XOUT_L        0x44   // R  

#define MPU9150_GYRO_YOUT_H        0x45   // R  

#define MPU9150_GYRO_YOUT_L        0x46   // R  

#define MPU9150_GYRO_ZOUT_H        0x47   // R  

#define MPU9150_GYRO_ZOUT_L        0x48   // R  

#define MPU9150_EXT_SENS_DATA_00   0x49   // R  

#define MPU9150_EXT_SENS_DATA_01   0x4A   // R  

#define MPU9150_EXT_SENS_DATA_02   0x4B   // R  

#define MPU9150_EXT_SENS_DATA_03   0x4C   // R  

#define MPU9150_EXT_SENS_DATA_04   0x4D   // R  

#define MPU9150_EXT_SENS_DATA_05   0x4E   // R  

#define MPU9150_EXT_SENS_DATA_06   0x4F   // R  

#define MPU9150_EXT_SENS_DATA_07   0x50   // R  

#define MPU9150_EXT_SENS_DATA_08   0x51   // R  

#define MPU9150_EXT_SENS_DATA_09   0x52   // R  

#define MPU9150_EXT_SENS_DATA_10   0x53   // R  

#define MPU9150_EXT_SENS_DATA_11   0x54   // R  

#define MPU9150_EXT_SENS_DATA_12   0x55   // R  

#define MPU9150_EXT_SENS_DATA_13   0x56   // R  

#define MPU9150_EXT_SENS_DATA_14   0x57   // R  

#define MPU9150_EXT_SENS_DATA_15   0x58   // R  

#define MPU9150_EXT_SENS_DATA_16   0x59   // R  

#define MPU9150_EXT_SENS_DATA_17   0x5A   // R  

#define MPU9150_EXT_SENS_DATA_18   0x5B   // R  

#define MPU9150_EXT_SENS_DATA_19   0x5C   // R

#define MPU9150_EXT_SENS_DATA_20   0x5D   // R  

#define MPU9150_EXT_SENS_DATA_21   0x5E   // R  

#define MPU9150_EXT_SENS_DATA_22   0x5F   // R  

#define MPU9150_EXT_SENS_DATA_23   0x60   // R  

#define MPU9150_MOT_DETECT_STATUS  0x61   // R  

#define MPU9150_I2C_SLV0_DO        0x63   // R/W

#define MPU9150_I2C_SLV1_DO        0x64   // R/W

#define MPU9150_I2C_SLV2_DO        0x65   // R/W

#define MPU9150_I2C_SLV3_DO        0x66   // R/W

#define MPU9150_I2C_MST_DELAY_CTRL 0x67   // R/W

#define MPU9150_SIGNAL_PATH_RESET  0x68   // R/W

#define MPU9150_MOT_DETECT_CTRL    0x69   // R/W

#define MPU9150_USER_CTRL          0x6A   // R/W

#define MPU9150_PWR_MGMT_1         0x6B   // R/W

#define MPU9150_PWR_MGMT_2         0x6C   // R/W

#define MPU9150_FIFO_COUNTH        0x72   // R/W

#define MPU9150_FIFO_COUNTL        0x73   // R/W

#define MPU9150_FIFO_R_W           0x74   // R/W

#define MPU9150_WHO_AM_I           0x75   // R

//MPU9150 Compass

#define MPU9150_CMPS_XOUT_L        0x4A   // R

#define MPU9150_CMPS_XOUT_H        0x4B   // R

#define MPU9150_CMPS_YOUT_L        0x4C   // R

#define MPU9150_CMPS_YOUT_H        0x4D   // R

#define MPU9150_CMPS_ZOUT_L        0x4E   // R

#define MPU9150_CMPS_ZOUT_H        0x4F   // R

// I2C address 0x69 could be 0x68 depends on your wiring.

int MPU9150_I2C_ADDRESS = 0x68;

// Variables to define gyro and accel biases

double gyro_bias[3]={0};

double acc_bias[3]={0};

// Variables where our values can be stored

double cmps[3]={0};

double acc[3]={0};

double gyro[3]={0};

// State Variables

double euler[3]={0};

double pos[3]={0};

double vel[3]={0};

// Time Variables

unsigned long time=0,time_prev=0;

// Start of Main Program

void setup()

{

    // Initialize the Serial Bus for printing data.

    Serial.begin(115200);

        

    // Initialize the 'Wire' class for the I2C-bus.

    Wire.begin();

    // Clear the 'sleep' bit to start the sensor.

    MPU9150_write(MPU9150_PWR_MGMT_1, 0);

    MPU9150_setupCompass();

        

        delay(2000);

}

void loop()

{

    // Temperature

    double dT = ((double)MPU9150_read(MPU9150_TEMP_OUT_L, MPU9150_TEMP_OUT_H) + 12412.0) / 340.0;

        

        // Magnetometer

        int mx=MPU9150_read(MPU9150_CMPS_XOUT_L, MPU9150_CMPS_XOUT_H);

        int my=MPU9150_read(MPU9150_CMPS_YOUT_L, MPU9150_CMPS_YOUT_H);

        int mz=MPU9150_read(MPU9150_CMPS_ZOUT_L, MPU9150_CMPS_ZOUT_H);

        

        // Gyro Rates

        int p= MPU9150_read(MPU9150_GYRO_XOUT_L, MPU9150_GYRO_XOUT_H);

        int q= MPU9150_read(MPU9150_GYRO_YOUT_L, MPU9150_GYRO_YOUT_H);

        int r= MPU9150_read(MPU9150_GYRO_ZOUT_L, MPU9150_GYRO_ZOUT_H);

        

        // Accelerometer

        int ax=MPU9150_read(MPU9150_ACCEL_XOUT_L, MPU9150_ACCEL_XOUT_H);

        int ay=MPU9150_read(MPU9150_ACCEL_YOUT_L, MPU9150_ACCEL_YOUT_H);

        int az=MPU9150_read(MPU9150_ACCEL_ZOUT_L, MPU9150_ACCEL_ZOUT_H);

        

        // Get floating point values

        acc[0]=(double)ax/16384*9.81-acc_bias[0];

        acc[1]=(double)ay/16384*9.81-acc_bias[1];

        acc[2]=(double)az/16384*9.81-acc_bias[2];

        double a[3]={0};

        

        gyro[0]=(double)p/131*PI/180-gyro_bias[0];

        gyro[1]=(double)q/131*PI/180-gyro_bias[1];

        gyro[2]=(double)r/131*PI/180-gyro_bias[2];

        

        cmps[0]=(double)mx*0.3;

        cmps[1]=(double)my*0.3;

        cmps[2]=(double)mz*0.3;

       

        Serial.print("T=");Serial.println(dT);

        Serial.print("ax=");Serial.println(acc[0],4);

        Serial.print("ay=");Serial.println(acc[1],4);

        Serial.print("az=");Serial.println(acc[2],4);

        Serial.print("p=");Serial.println(gyro[0],4);

        Serial.print("q=");Serial.println(gyro[1],4);

        Serial.print("r=");Serial.println(gyro[2],4);

        Serial.print("mx=");Serial.println(cmps[0],4);

        Serial.print("my=");Serial.println(cmps[1],4);

        Serial.print("mz=");Serial.println(cmps[2],4);

       

        Serial.println("%%%%%%%%%% End of Time Step%%%%%%%%%%");

        Serial.println("");

        

    delay(10);

}

 

// Set up Compass only once

void MPU9150_setupCompass(){

    

        int tempAddress = MPU9150_I2C_ADDRESS; //temporarily store mpu9150 i2c address as it will later be modified

    MPU9150_I2C_ADDRESS = 0x0C;      //change Address to Compass    

    MPU9150_write(0x0A, 0x00); //PowerDownMode

    MPU9150_write(0x0A, 0x0F); //SelfTest

    MPU9150_write(0x0A, 0x00); //PowerDownMode

    //MPU9150_I2C_ADDRESS = 0x68;      //change Address to MPU

    MPU9150_I2C_ADDRESS = tempAddress; //new version to revert to original address

    MPU9150_write(0x24, 0x40); //Wait for Data at Slave0

    MPU9150_write(0x25, 0x8C); //Set i2c address at slave0 at 0x0C

    MPU9150_write(0x26, 0x02); //Set where reading at slave 0 starts

    MPU9150_write(0x27, 0x88); //set offset at start reading and enable

    MPU9150_write(0x28, 0x0C); //set i2c address at slv1 at 0x0C

    MPU9150_write(0x29, 0x0A); //Set where reading at slave 1 starts

    MPU9150_write(0x2A, 0x81); //Enable at set length to 1

    MPU9150_write(0x64, 0x01); //overvride register

    MPU9150_write(0x67, 0x03); //set delay rate

    MPU9150_write(0x01, 0x80);

    MPU9150_write(0x34, 0x04); //set i2c slv4 delay

    MPU9150_write(0x64, 0x00); //override register

    MPU9150_write(0x6A, 0x00); //clear usr setting

    MPU9150_write(0x64, 0x01); //override register

    MPU9150_write(0x6A, 0x20); //enable master i2c mode

    MPU9150_write(0x34, 0x13); //disable slv4

}

////////////////////////////////////////////////////////////

///////// I2C functions to get easier all values ///////////

////////////////////////////////////////////////////////////

int MPU9150_read(int addrL, int addrH){

    Wire.beginTransmission(MPU9150_I2C_ADDRESS);

    Wire.write(addrL);

    Wire.endTransmission(false);

    Wire.requestFrom(MPU9150_I2C_ADDRESS, 1, true);

    byte L = Wire.read();

    Wire.beginTransmission(MPU9150_I2C_ADDRESS);

    Wire.write(addrH);

    Wire.endTransmission(false);

    Wire.requestFrom(MPU9150_I2C_ADDRESS, 1, true);

    byte H = Wire.read();

    return (H << 8) + L;

}

int MPU9150_write(int addr, int data){

    Wire.beginTransmission(MPU9150_I2C_ADDRESS);

    Wire.write(addr);

    Wire.write(data);

    Wire.endTransmission(true);

    return 1;

}

Im also trying to access the magnetometer data from the mpu9150 but Im not too sure why they used external data registers for the compass. For example the mpu9150 register map says the data register are addressed from 0x03 to 0x08 (outputs x,y,z components) but the this arduino example says the data register are " 0x4A ,  0x4B,  0x4AC,  ...etc"

 

Is there a separate slave address for the magnetometer? Looking at the datasheet for the MPU9150, I can only find a "Device ID" given as 0x48 not the 0x0C shown in this particular example; I am so confused. 

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  • 10 months later...
tdg_engimusing Newbie

tdg_engimusing

Posted
Posted

I was unable to get any of the examples (including the one in this thread) I found online to work either. In the end I ended up using the I2C bypass to access the magnetometer raw data.

First change the compass defines to point at the registers for the Compass instead of the MPU9150's registers: 

//MPU9150 Compass
#define MPU9150_CMPS_XOUT_L        0x03   // R
#define MPU9150_CMPS_XOUT_H        0x04   // R
#define MPU9150_CMPS_YOUT_L        0x05   // R
#define MPU9150_CMPS_YOUT_H        0x06   // R
#define MPU9150_CMPS_ZOUT_L        0x07   // R
#define MPU9150_CMPS_ZOUT_H        0x08   // R
#define MPU9150_CMPS_CNTL       0x0A   // R

Then setupCompass() gets simplified down to just: 

void MPU9150_setupCompass(){ 
  MPU9150_write(MPU9150_USER_CTRL, 0x00); //Disable Master Aux I2C mode

  MPU9150_write(MPU9150_INT_PIN_CFG, 0x02); //Enable I2C Aux Bypass mode

  MPU9150_I2C_ADDRESS = 0x0C;      //change Address to Compass    

  writeSensor(MPU9150_CMPS_CNTL, 0x01); //Single Read Mode
  delay(10);

  MPU9150_I2C_ADDRESS = tempAddress; //new version to revert to original address
}

That sets up the Aux I2C to be connected directly to the main I2C. Then to read the values from the compass just do something along these lines: 

void MPU9150Device::readCompassData(int &compassX, int &compassY, int &compassZ)
{
  MPU9150_I2C_ADDRESS = MPU9150_CMPS_ADDRESS;      //change Adress to Compass

  writeSensor(MPU9150_CMPS_CNTL, 0x01); //trigger single read
  delay(10);

  compassX = MPU9150_read(MPU9150_CMPS_XOUT_L,MPU9150_CMPS_XOUT_H);
  compassY = MPU9150_read(MPU9150_CMPS_YOUT_L,MPU9150_CMPS_YOUT_H);
  compassZ = MPU9150_read(MPU9150_CMPS_ZOUT_L,MPU9150_CMPS_ZOUT_H);

  MPU9150_I2C_ADDRESS = MPU9150_I2C_ADDRESS;      //change Adress to MPU
}

The datasheet and register map documents here: https://www.invensense.com/products/motion-tracking/9-axis/mpu-9150/ Helped out a lot. 

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