How to disable buffer in Nordic Uart Service?

[hermann]

I'm trying to replace a RS232 cable with a BLE bridge with the Nordic Uart Service.

One nRF52832 configured as central (app_uart_example_central) and an other one as peripheral. The connection is working well with putty or the nRF connect app on the phone. But there is a 60 character buffer and I can't find the code to change it.

Does someone know how to disable that buffer to send incoming data as it comes?

Details: Chip: nRF52832 IDE: Keil5.23 Softdevice: s132

[hermann]

Hi Torbjørn,

thanks for your tip with the timer.

I created a app_timer (single_shot) which is (re-)started after a recieved byte on the UART. So the last bytes in the buffer are send after a few ticks. But sometimes there are delays which are a lot longer than the timer should be.

void uart_event_handle(app_uart_evt_t * p_event)
{
static uint8_t data_array[BLE_NUS_MAX_DATA_LEN];
static uint8_t index = 0;
uint32_t       err_code;

switch (p_event->evt_type)
{
  // event is called when timer expiers
		  case APP_CLEAR_BUFFER:
				  //copy of APP_UART_DATA_READY without getting byte from UART --> no new byte there...
        if (index != 0)
        {
            NRF_LOG_DEBUG("Ready to send data over BLE NUS\r\n");
            NRF_LOG_HEXDUMP_DEBUG(data_array, index);

            do
            {
                err_code = ble_nus_string_send(&m_nus, data_array, index);
                if ( (err_code != NRF_ERROR_INVALID_STATE) && (err_code != NRF_ERROR_BUSY) )
                {
                    APP_ERROR_CHECK(err_code);
                }
            } while (err_code == NRF_ERROR_BUSY);

            index = 0;
        }
        break;				
		
		case APP_UART_DATA_READY:
                    // ...
   }

Any idea what causes this delay?

[ovrebekk]

Hi Hermann

Have you modified the UART driver to do the timeout internally?

It's hard to say why the problem occurs, but I assume it is related to how the app_timer callback is reset if you receive more data before the timeout should occur.

I think it would be simpler from a logical standpoint to use a repeated timer instead, and check the state of the buffer in the timer, sending a packet if the buffer contains more than 0 bytes.

Best regards
Torbjørn

[lm]

Hello, do you have news fr this post? thank you

[ovrebekk]

Hi

Is that a question for me or Hermann?

Since he hasn't responded to the case I consider it resolved. 

If you have a related UART issue I recommend opening a new ticket. 

Best regards
Torbjørn

[lm]

Hello, yes that was a question for you actually I would like to have your help about how to clear the buffer after all the info is transmitted. Thank you 

[ovrebekk]

Hi 

The UART buffers can be cleared using the app_uart_flush() function, if that is what you mean. 

Best regards
Torbjørn

[lm]

thank you so much