Read MPU 9250 magnetometer

[Swapnil]

Hello,

I want to read the values from MPU9250 magnetometer i.e. from AK8963 I wrote a function just like accelerometer and gyroscope shown below:

uint32_t mpu_read_mag(mag_values_t * mag_values)

  {

    uint32_t err_code;
    uint8_t raw_values[6];
    err_code = mpu_read_registers1(REG_ST1, raw_values, 6);
    if(err_code != NRF_SUCCESS) return err_code;
    uint8_t *data;
    data = (uint8_t*)mag_values;
    for(uint8_t i = 0; i<6; i++)
    {
        *data = raw_values[5-i];
        data++;
    }
    return NRF_SUCCESS;
}

and then wrote separate function for mpu_read_register for giving separate AK8963 address shown below:

uint32_t mpu_read_registers1(uint8_t reg, uint8_t * p_data, uint32_t length)
{

    uint32_t err_code;
    uint32_t timeout = MPU_TWI_TIMEOUT;

    err_code = nrf_drv_twi_tx(&m_twi_instance, AK8963_ADDR, &reg, 1, false);
    if(err_code != NRF_SUCCESS) return err_code;

    while((!twi_tx_done) && --timeout);
    if(!timeout) return NRF_ERROR_TIMEOUT;
    twi_tx_done = false;

    err_code = nrf_drv_twi_rx(&m_twi_instance, AK8963_ADDR, p_data, length);
    if(err_code != NRF_SUCCESS) return err_code;

    timeout = MPU_TWI_TIMEOUT;
    while((!twi_rx_done) && --timeout);
    if(!timeout) return NRF_ERROR_TIMEOUT;
    twi_rx_done = false;

    return err_code;
}

Program gets compiled but doesn't show any output.

[robert]

Think you need to head over to the invensense forums for help on the MPU9250.

[Petter Myhre]

What doesn't show any output? Have you tried to debug? Are you able to communicate with the sensor at all? Have you connected a logic analyzer to see what is happening on the lines?

[Swapnil]

I got the output correctly at CSR board, and I know how this sensor works. I am not getting any output for magnetometer on Nordic Dev. board. I am getting values of accelerometer and gyroscope but when i give the address of AK8963 then i am not able to communicate

[MartinBL]

I have never tried to use the magnetometer. What is the AK8963_ADDR value? Do you get error codes returned from the twi transfer functions? I haven't had the time to look into the datasheets, but I think you might have to enable the magnetometer in the configuration registers before you can use it.

[Swapnil]

The AK8963_ADDR value is 0x0C. I don't get any error codes. I also configured the control register of AK8963:

err_code = mpu_write_register(REG_CNTL_1, 0x00);
if(err_code != NRF_SUCCESS) return err_code;
err_code = mpu_write_register(REG_CNTL_1, 0x04);
if(err_code != NRF_SUCCESS) return err_code;