Missing APP_UART_TX_EMPTY event

[Mattias]

Hi!

I am working with an application were two nRF52832 shall communicate over UART in half-duplex 1-wire mode (similar to what is described here but I use different pins for Tx/Rx: devzone.nordicsemi.com/.../). The FIFO version of app_uart (app_uart_fifo.c) and SDK 13.0.0 is used.

APP_UART_TX_EMTY is used to check that data been sent before Tx pin is switched to input mode. The problem I am facing is that I don't get the event if I just use app_uart_put() to transmit single data bytes from unit 1 to unit 2. But if I add printf("\r\n") the event occur as expected. I have verified with oscilloscope that first data byte is sent. Code snippets are shown below.

    void uart_event_handler(app_uart_evt_t * p_event)
    {
        if (p_event->evt_type == APP_UART_COMMUNICATION_ERROR)
        {
            APP_ERROR_HANDLER(p_event->data.error_communication);
        }
        else if (p_event->evt_type == APP_UART_FIFO_ERROR)
        {
            APP_ERROR_HANDLER(p_event->data.error_code);
        }
        else if (p_event->evt_type == APP_UART_TX_EMPTY)
        {
            tx_empty_flag = true;
        }
        else if (p_event->evt_type == APP_UART_DATA_READY)
        {
            data_ready_flag = true;
        }
    }
    
    
    
    while (true)
    {
       while (app_uart_put('A') != NRF_SUCCESS);
       printf("\r\n");  // no APP_UART_TX_EMPTY is received in uart_event_handler if line deleted 
    
       while (tx_empty_flag != true );
       tx_empty_flag = false;
       disable_tx();  
    
    }

Could anyone explain this?

Thanks in advance, Mattias

[Mattias]

Thanks Martin

Your right about APP_UART_TX_EVENT, it should of course be APP_UART_TX_EMPTY. I have corrected that now.

1. UART initialization:

   int main(void) { uint32_t err_code; bsp_board_leds_init();

    const app_uart_comm_params_t comm_params =
     {
          RX_PIN_NUMBER,
          TX_PIN_NUMBER,
          RTS_PIN_NUMBER,
          CTS_PIN_NUMBER,
          APP_UART_FLOW_CONTROL_DISABLED,
          false,
          UART_BAUDRATE_BAUDRATE_Baud115200
      };
   
      APP_UART_FIFO_INIT(&comm_params,
      UART_RX_BUF_SIZE,
      UART_TX_BUF_SIZE,
      uart_event_handler,
      APP_IRQ_PRIORITY_HIGH,
      err_code);
   
    APP_ERROR_CHECK(err_code);