C I2C code to read sensor data from MPU9150 not working

3
votes

I am trying to read the MPU9150 sensor data over I2C using an LPC1343 microcontroller. I have developed the following C code, however, I receive zero when reading the value of say accelerometer X low bits. Here is my code:

/////////////// MPU9150 I2C CODE /////////////////////
 #define MPU9150_SELF_TEST_X        0x0D   // R/W
#define MPU9150_SELF_TEST_Y        0x0E   // R/W
#define MPU9150_SELF_TEST_Z        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

#define MPU9150_READBIT 0x01 

// I2C address 0x69 could be 0x68 depends on your wiring. 
int MPU9150_ADDRESS = 0x68;

typedef enum
{
  MPU9150_ERROR_OK = 0,                // Everything executed normally
  MPU9150_ERROR_I2CINIT = 1,               // Unable to initialise I2C
  MPU9150_ERROR_I2CBUSY = 2,               // I2C already in use
  MPU9150_ERROR_NOCONNECTION = 3,          // Unable to read device ID during init
  MPU9150_ERROR_LAST = 4
}
MPU9150Error_t;

MPU9150Error_t MPU9150Init(void);
MPU9150Error_t MPU9150GetDeviceID(uint8_t *id);
MPU9150Error_t MPU9150GetXYZ(int16_t *accX, int16_t *accY, int16_t *accZ, int16_t *gyroX, int16_t *gyroY, int16_t *gyroZ);

extern volatile uint8_t   I2CMasterBuffer[I2C_BUFSIZE];
extern volatile uint8_t   I2CSlaveBuffer[I2C_BUFSIZE];
extern volatile uint32_t  I2CReadLength, I2CWriteLength;

static bool _MPU9150Initialised = false;

/**************************************************************************/
/*! 
    @brief  Sends a single command byte over I2C
*/
/**************************************************************************/
static MPU9150Error_t MPU9150Write8 (uint8_t reg, uint8_t value)
{
  MPU9150Error_t error = MPU9150_ERROR_OK;

  // Clear write buffers
  uint32_t i;
  for ( i = 0; i < I2C_BUFSIZE; i++ )
  {
    I2CMasterBuffer[i] = 0x00;
  }

  I2CWriteLength = 3;
  I2CReadLength = 0;
  I2CMasterBuffer[0] = MPU9150_ADDRESS;       // I2C device address
  I2CMasterBuffer[1] = reg;                   // Register
  I2CMasterBuffer[2] = value;
  i2cEngine();

  // ToDo: Add in proper I2C error-checking
  return error;
}

/**************************************************************************/
/*! 
    @brief  Reads a 16 bit values over I2C
*/
/**************************************************************************/
static MPU9150Error_t MPU9150Read8(uint8_t reg, uint8_t *value)
{
  MPU9150Error_t error = MPU9150_ERROR_OK;

  // Clear write buffers
  uint32_t i;
  for ( i = 0; i < I2C_BUFSIZE; i++ )
  {
    I2CMasterBuffer[i] = 0x00;
  }

  I2CWriteLength = 2;
  I2CReadLength = 1;
  I2CMasterBuffer[0] = MPU9150_ADDRESS;         // I2C device address
  I2CMasterBuffer[1] = reg;                     // Command register
  // Append address w/read bit
  I2CMasterBuffer[2] = MPU9150_ADDRESS | MPU9150_READBIT;  
  i2cEngine();

  // Shift values to create properly formed integer
  *value = I2CSlaveBuffer[0];

  // ToDo: Add in proper I2C error-checking
  return error;
}

/**************************************************************************/
/*! 
    @brief  Initialises the I2C block
*/
/**************************************************************************/
MPU9150Error_t MPU9150Init(void)
{

  MPU9150Error_t error = MPU9150_ERROR_OK;

  // Initialise I2C
  if (i2cInit(I2CMASTER) == false)
  {
    return MPU9150_ERROR_I2CINIT;    /* Fatal error */
  }

  error = MPU9150Write8(MPU9150_PWR_MGMT_1, 0);
  //TODO - MPU9150_setupCompass(); if we want mag

  _MPU9150Initialised = true;
  return error;
}

/**************************************************************************/
/*! 
    @brief  Gets the latest X/Y/Z values
*/
/**************************************************************************/
MPU9150Error_t MPU9150GetXYZ(int16_t *accX, int16_t *accY, int16_t *accZ, int16_t *gyroX, int16_t *gyroY, int16_t *gyroZ )
{
  MPU9150Error_t error = MPU9150_ERROR_OK;

  uint8_t L = 0; uint8_t H = 0;

  error += MPU9150Read8(MPU9150_ACCEL_XOUT_L, &L);
  error += MPU9150Read8(MPU9150_ACCEL_XOUT_H, &H);
  *accX = (H<<8)+L; 

  error += MPU9150Read8(MPU9150_ACCEL_YOUT_L, &L);
  error += MPU9150Read8(MPU9150_ACCEL_YOUT_H, &H);
  *accY = (H<<8)+L;

  error += MPU9150Read8(MPU9150_ACCEL_ZOUT_L, &L);
  error += MPU9150Read8(MPU9150_ACCEL_ZOUT_H, &H);
  *accZ = (H<<8)+L;

  error += MPU9150Read8(MPU9150_GYRO_XOUT_L, &L);
  error += MPU9150Read8(MPU9150_GYRO_XOUT_H, &H);
  *gyroX = (H<<8)+L;

  error += MPU9150Read8(MPU9150_GYRO_YOUT_L, &L);
  error += MPU9150Read8(MPU9150_GYRO_YOUT_H, &H);
  *gyroY = (H<<8)+L;

  error += MPU9150Read8(MPU9150_GYRO_ZOUT_L, &L);
  error += MPU9150Read8(MPU9150_GYRO_ZOUT_H, &H);
  *gyroZ = (H<<8)+L;

  return error;
}

And in my main function I am testing it as follows:

I2Cerr = MPU9150Init(); 

//now in my while(1) loop:

I2Cerr = MPU9150GetXYZ(&aX, &aY, &aZ, &gX, &gY, &gZ);
uint8_t test = 55;
I2Cerr =  MPU9150Read8(MPU9150_ACCEL_XOUT_L, &test); //always reads 0 into &arg???

For reference, the code base I started from is https://github.com/microbuilder/LPC1343CodeBase

I am modifying an example I2C driver from an LPC example using the ADXL345 accelerometer: https://github.com/microbuilder/LPC1343CodeBase/blob/master/drivers/sensors/adxl345/adxl345.c as well as using MPU9150 specifics from this example Arduino code: http://playground.arduino.cc/Main/MPU-9150

This is a rather involved firmware question, so many thanks for any help on what could be going wrong.

EDIT - adding in the code for the i2cEngine() function:

uint32_t i2cEngine( void ) 
{
  I2CMasterState = I2CSTATE_IDLE;
  RdIndex = 0;
  WrIndex = 0;
  if ( I2CStart() != TRUE )
  {
    I2CStop();
    return ( FALSE );
  }

  /* wait until the state is a terminal state */
  while (I2CMasterState < 0x100);

  return ( I2CMasterState );
}
1
cembeddedsensorsi2cfirmware
Can you post the code for i2cEngine()? It seems suspicious to me that in MPU9150Read8() you set I2CWriteLength = 2 but then you load I2CMasterBuffer[] with three bytes. Does i2cEngine() send that third byte for the read operation? – kkrambo
i2cEngine() code is posted now. To me the function doesn't look that insightful but hopefully it helps. If you think digging into the i2c.c file will help, it's available here: github.com/microbuilder/LPC1343CodeBase/blob/master/core/i2c/… – JDS
Are you able to successfully read credible values for any I2C register? Have you been able to personally verify the I2C code and I/O setup against any other target? Can you check for activity on the lines with a scope or even audible logic probe? – Chris Stratton
@ChrisStratton No not yet. Unfortunately this is on a hand-soldered board using an LPC1343 breakout board and the MPU9150 breakout board. I am using a logic probe to check values on SDA/SCL, will report back soon. – JDS
Yikes. Those mass storage solutions look cute, but probably aren't the most efficient. Can you find a cheap SWD solution? For the comparable ST cortex-M chips I use, any of their $10-20 eval boards functions as a low pint count JTAG debug interface. I'd at the least try to get my debug output channel to a wired one, with a TTL USB-serial cable or something. – Chris Stratton

1 Answers

2
votes

Looking at the datasheet (http://www.invensense.com/mems/gyro/documents/PS-MPU-9150A-00v4_3.pdf, p35) it looks like you need to be sending repeat starts, ie start->dev_address->register_to_read->start->dev_address->read_data->stop. Many I2C implementations don't support repeated start (ie a stop must always be matched with a start) but the hardware itself almost always does. This may be the case for your implementation, but it's hard to well what i2cEngine() is doing without more context (eg i2cStart, i2cStop, and ISRs involved in i2c).