Corrupted TX data when using libuarte_async library

[rchaudet]

Hi everyone,

Because of experiencing stability issues using the app_uart implementation for UART communication, I recently switched to the libuarte_async lib which works like a charm when dealing with reception of data. I started from the libuarte example from SDK 17.0.2 with dev board pca10040. 

receiving data is always consistent, but whenever I want to send data, it actually sends random bytes instead (but the correct number of bytes).

 Here is my main function:

int main(void)
{
    bsp_board_init(BSP_INIT_LEDS);
    
    ret_code_t ret = nrf_drv_clock_init();
    APP_ERROR_CHECK(ret);
  
    nrf_drv_clock_lfclk_request(NULL);

    ret_code_t err_code = NRF_LOG_INIT(app_timer_cnt_get);
    APP_ERROR_CHECK(err_code);

    NRF_LOG_DEFAULT_BACKENDS_INIT();

    nrf_libuarte_async_config_t nrf_libuarte_async_config = {
            .tx_pin     = TX_PIN_NUMBER,
            .rx_pin     = RX_PIN_NUMBER,
            .baudrate   = NRF_UARTE_BAUDRATE_115200,
            .parity     = NRF_UARTE_PARITY_EXCLUDED,
            .hwfc       = NRF_UARTE_HWFC_DISABLED,
            .timeout_us = 100,
            .int_prio   = APP_IRQ_PRIORITY_LOW
    };

    err_code = nrf_libuarte_async_init(&libuarte, &nrf_libuarte_async_config, uart_event_handler, (void *)&libuarte);

    APP_ERROR_CHECK(err_code);

    nrf_libuarte_async_enable(&libuarte);

    uint8_t data[] = {0x41,0x54,0x2B,0x51,0x43,0x43,0x49,0x44,0x0D};
    ret = nrf_libuarte_async_tx(&libuarte, data, sizeof(data));
    APP_ERROR_CHECK(ret);

    while (true)
    {
        NRF_LOG_FLUSH();
    }
}

And uart instance is created this way:

NRF_LIBUARTE_ASYNC_DEFINE(libuarte, 0, 0, 0, NRF_LIBUARTE_PERIPHERAL_NOT_USED, 255, 3);

Any idea what could be the issue?

Best regards

[Jørgen Holmefjord]

Hi,

Do you have the UART backend enabled for NRF_LOG? The UART TX pin (P0.06) is used by default for the UART logger backend, which may interfere with the transfer if used at the same time. Although, this should give an error code if both are configured to use the same UART instance-

I would also try to declare the data-variable globally, although it seems to be in scope from your code snippet.

Can you post a logic trace from the UART pins, or an example of the data being output?

Best regards,
Jørgen

[Jørgen Holmefjord]

I integrated your code int the LibUARTE example from the SDK, and I get "AT+QCCID" on the terminal when I run it on a nRF52 DK (PCA10040). Is this the only code you have in your application?

Could there be something else in the application that overwrites the data buffer?

[rchaudet]

I found the issue: it was coming from the device dev board is connected to. RX line was held high by another serial component :(

Libuarte is working just as expected in TX & RX.

Thank you for taking the time to check.