Problems with TWI and NRF_LOG_DEFAULT_BACKENDS_INIT() at the same time

[Arne Laugstøl]

Hi

I discovered I strange behaviour using twi. I am using sdk-14.2.0, and Segger Studio. I started with the twi_scanner projected that I found in examples/peripherals. I have shortened it to demonstrate the problem I discovered.

The example as shown below works fine. It communicate with my digital potmeter at address 0x2f. When I look at the logic-analyzer I can see that the sda and scl lines works fine.

However, if I uncomment NRF_LOG_DEFAULT_BACKENDS_INIT(), the twi interface don't drive the SDA line any more.

Do you have any explanation of this unexpected behaviour?

Regards Arne

#define TWI_INSTANCE_ID     0
static const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(TWI_INSTANCE_ID);

void twi_init (void)
{
    ret_code_t err_code;
    const nrf_drv_twi_config_t twi_config = {
       .scl                = 7,
       .sda                = 6,
       .frequency          = NRF_TWI_FREQ_400K,
       .interrupt_priority = APP_IRQ_PRIORITY_HIGH,
       .clear_bus_init     = false,
       .hold_bus_uninit    = false
    };

    err_code = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
    APP_ERROR_CHECK(err_code);
    nrf_drv_twi_enable(&m_twi);
}

int main(void)
{
    ret_code_t err_code;
    uint8_t address;
    uint8_t sample_data;

    APP_ERROR_CHECK(NRF_LOG_INIT(NULL));
    //NRF_LOG_DEFAULT_BACKENDS_INIT();

    twi_init();

    address=0x2f; // Potmeter
    err_code = nrf_drv_twi_rx(&m_twi, address, &sample_data, sizeof(sample_data));
    if (err_code == NRF_SUCCESS)
    {
        NRF_LOG_INFO("TWI device detected at address 0x%x.", address);
    }
    NRF_LOG_FLUSH()
}

[Sigurd]

Hi,

If you want to turn off logging, you should set NRF_LOG_ENABLED to 0 in sdk_config.h.

If NRF_LOG_ENABLED is on, and with either NRF_LOG_BACKEND_RTT_ENABLED or NRF_LOG_BACKEND_UART_ENABLED also on, you will get stuck in the logging backend because you have not initialized the backend with NRF_LOG_DEFAULT_BACKENDS_INIT().