BLE UART losing packets

[kian79]

Hi all,

I am using PCA10040 with nRF5_SDK_13.0.0 and using the ble_perpheral -> ble_app_uart example.

I am trying to stream data from UART to an android phone and the data is coming from an external MCU with its TX/RX pin connected to the RX/TX pin on the NRF52DK. Every 40ms, I am sending a line of characters up to 49 bytes (max), terminating with a new line character.

Somehow, the android app is not able to receive the data and it only able to receive 1 out of every 3 lines of characters, and this is very consistent. Here is the log file from the app:

10:12:52.531 "4 111 222 333 211564 212372 212076 999999 0" received I 10:12:52.550 Notification received from 6e400003-b5a3-f393-e0a9-e50e24dcca9e, value: (0x) 37-09-31-31-31-09-32-32-32-09-33-33-33-09-32-31-31-35-30-37-09-32-31-32-34-30-33-09-32-31-32-30-36-34-09-33-32-36-34-35-09-30-0D-0A

10:12:52.572 "7 111 222 333 211507 212403 212064 32645 0" received I 10:12:52.596 Notification received from 6e400003-b5a3-f393-e0a9-e50e24dcca9e, value: (0x) 31-30-09-31-31-31-09-32-32-32-09-33-33-33-09-32-31-31-35-31-35-09-32-31-32-33-33-31-09-32-31-32-30-38-31-09-33-32-33-30-30-09-30-0D-0A

10:12:52.621 "10 111 222 333 211515 212331 212081 32300 0" received I 10:12:52.643 Notification received from 6e400003-b5a3-f393-e0a9-e50e24dcca9e, value: (0x) 31-33-09-31-31-31-09-32-32-32-09-33-33-33-09-32-31-31-35-32-30-09-32-31-32-33-36-36-09-32-31-32-30-34-34-09-33-32-33-31-31-09-30-0D-0A
A 10:12:52.662 "13 111 222 333 211520 212366 212044 32311 0

It basically receiving the 4th, 7th, 10th line etc, and losing the 5th, 6th, 8th, 9th etc lines. Can anyone advise on how this problem can be solved?

Thanks in advance!

[Petter Myhre]

Are you checking the returned error code of ble_nus_string_send()? Is it always NRF_SUCCESS (0x00000000)?

[kian79]

Hi Petter,

The default codes does the following:

        case APP_UART_DATA_READY:
            UNUSED_VARIABLE(app_uart_get(&data_array[index]));
            index++;

            if ((data_array[index - 1] == '\n') || (index >= (m_ble_nus_max_data_len)))
            {
                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;

The do-while loop is constantly checking for NRF_ERROR_BUSY. I presume its constantly trying to send the string until successful then it breaks out of the do-while loop. Perhaps this is taking too much time and hence its losing packets inbetween?

If so, is there anyway to rectify the problem? I think it should be able to transfer much faster than that!