How to disable buffer in Nordic Uart Service?

RE: How to disable buffer in Nordic Uart Service?

lm — Fri, 18 Feb 2022 07:56:12 GMT

thank you so much

RE: How to disable buffer in Nordic Uart Service?

ovrebekk — Fri, 18 Feb 2022 07:53:09 GMT

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

Best regards
Torbjørn

RE: How to disable buffer in Nordic Uart Service?

lm — Wed, 16 Feb 2022 07:23:03 GMT

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

RE: How to disable buffer in Nordic Uart Service?

ovrebekk — Tue, 15 Feb 2022 19:07:10 GMT

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

RE: How to disable buffer in Nordic Uart Service?

lm — Tue, 15 Feb 2022 14:58:29 GMT

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

RE: How to disable buffer in Nordic Uart Service?

ovrebekk — Mon, 31 Jul 2017 13:12:06 GMT

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

RE: How to disable buffer in Nordic Uart Service?

hermann — Mon, 10 Jul 2017 11:07:22 GMT

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?

RE: How to disable buffer in Nordic Uart Service?

ovrebekk — Mon, 26 Jun 2017 11:51:45 GMT

Hi Hermann

I don't think removing the buffer is the best option, since having the buffer is a good way to ensure you can send larger chunks of data at once, but what you can do is to add some code to empty the buffer more aggressively.

For instance you can set up an app_timer callback that checks the buffer every N milliseconds, and sends whatever is in the buffer as long as it is not empty. Then you know that your data will be sent on certain intervals, even if you haven't filled the buffer first.

Best regards
Torbjørn