[nRF51 to nRF52 Migration] TWI issues

[pmantri0412]

Hi,

I am currently migrating my controller from nRF51 to nRF52832 . I am facing an issue where in when I try to do an TWI communication with MPU9250 on nRF52 the code gets stuck in the TWI commands. 

I am using SDK12.3. 

The code that I am using to access the Sensor through nRF52 is same as the one used for accessing the sensor through nRF51. Can you let me know if I need to make any change to the TWI access instruction to allow for communication between nRF52 and MPU9250.

Thanks

[Kenneth]

Hi,

Can you first confirm that the twi example in SDKv12.3 works "as-is", just to rule out hardware issues (pins, pull-ups, address etc). 

Best regards,
Kenneth

[pmantri0412]

Hi Kenneth,

I used used the twi example in SDKv12.3 and modified the code to read the who am I register in MPU9250 .

I am getting an "NRF_ERROR_BUSY" error when I try to read the register. 

So the code progress all the way till line 44 and gets stuck there.

Here is the code snippet.

/**
 * @brief TWI initialization.
 */
void twi_init (void)
{
    ret_code_t err_code;

    const nrf_drv_twi_config_t twi_lm75b_config = {
       .scl                = SCL_PIN_NUMBER,
       .sda                = SDA_PIN_NUMBER,
       .frequency          = NRF_TWI_FREQ_400K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false
    };

    err_code = nrf_drv_twi_init(&m_twi, &twi_lm75b_config, twi_handler, NULL);
    APP_ERROR_CHECK(err_code);

    nrf_drv_twi_enable(&m_twi);
}

/**
 * @brief Function for reading data from MPU9250 sensor.
 */
static void read_whi_data()
{
    m_xfer_done = false;
    ret_code_t err_code;
    uint8_t data[2] ={0,0};

   
    err_code= nrf_drv_twi_tx(&m_twi,0x68,&who_am_i_reg,1,1);
    if (err_code!=NRF_SUCCESS)
    {
        CYAN_ON();
        while(1){}
    }

    BLUE_ON();
    
    err_code = nrf_drv_twi_rx(&m_twi,0x68,data,1);
    if (err_code == NRF_ERROR_BUSY)
    {
        WHITE_ON();
        while(1){}
    }

    if (data[0] == 0x71)
    {
        PURPLE_ON();
    }
    else
    {
        GREEN_ON();
    }

}

/**
 * @brief Function for main application entry.
 */
int main(void)
{
    LED_init();
    
    twi_init();
    
    RED_ON();
    nrf_delay_ms(1000);
    read_whi_data();
    while (true)
    {
        nrf_delay_ms(500);

        do
        {
            __WFE();
        }while (m_xfer_done == false);
    }
}

[pmantri0412]

I have 10K resistors pulling up my SCL and SDA lines to VDD. But when I check the voltage (without enabling TWI) my SDA is not pulled up to VDD.

I have connected SDA to pin 9 which is the NFC1 input. Does this cause any issues ? My SCL is connected to Pin 8 and that is pulled up to VDD.

[pmantri0412]

Ok, I believe the issue was that I was using the NCF 1 pin with disabling the NFC. Once I added the preprocessor directive CONFIG_NFCT_PINS_AS_GPIOS.

I was able to get the Sensor working.