app_ble_uart uart must be hooked up?

[berkutta]

I'm facing the issue, that the app_ble_uart example just works if I hook up TX/RX of my USB - UART converter. Is this a desired behaviour? It doesn't seem to start and advertise if I don't hook up TX/RX.

[Vidar Berg]

You may get a UART framings error if the RX pin becomes floating once you disconnect the USB-UART converter. To avoid this I would suggest to enable internal pull up on the RX pin after uart init.

/**@snippet [Handling the data received over UART] */


/**@brief  Function for initializing the UART module.
 */
/**@snippet [UART Initialization] */
static void uart_init(void)
{
    uint32_t                     err_code;
    app_uart_comm_params_t const comm_params =
    {
        .rx_pin_no    = RX_PIN_NUMBER,
        .tx_pin_no    = TX_PIN_NUMBER,
        .rts_pin_no   = RTS_PIN_NUMBER,
        .cts_pin_no   = CTS_PIN_NUMBER,
        .flow_control = APP_UART_FLOW_CONTROL_DISABLED,
        .use_parity   = false,
#if defined (UART_PRESENT)
        .baud_rate    = NRF_UART_BAUDRATE_115200
#else
        .baud_rate    = NRF_UARTE_BAUDRATE_115200
#endif
    };

    APP_UART_FIFO_INIT(&comm_params,
                       UART_RX_BUF_SIZE,
                       UART_TX_BUF_SIZE,
                       uart_event_handle,
                       APP_IRQ_PRIORITY_LOWEST,
                       err_code);
    APP_ERROR_CHECK(err_code);


    NRF_P0->PIN_CNF[RX_PIN_NUMBER] |= GPIO_PIN_CNF_PULL_Msk;
}
/**@snippet [UART Initialization] */

[berkutta]

Thanks, this was the issue!