RE: send and receive data over ble without character 0xDA (Enter)

user2116 — Mon, 23 May 2022 12:05:42 GMT

Hi Mohammad

If I understand you correctly you are sending data from LabView to a DK running the ble_app_uart example, which is connected to another DK over Bluetooth running the ble_app_uart_c example, and you see here that you don't get the full message that you sent from the PC side?

In this case it is the uart_event_handle function on the ble_app_uart side that is the problem, as it only transmits a packet if either the buffer fills up, or if the LF or CR character is received (0x0A or 0x0D):

/**@brief   Function for handling app_uart events.
 *
 * @details This function will receive a single character from the app_uart module and append it to
 *          a string. The string will be be sent over BLE when the last character received was a
 *          'new line' '\n' (hex 0x0A) or if the string has reached the maximum data length.
 */
/**@snippet [Handling the data received over UART] */
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)
    {
        case APP_UART_DATA_READY:
            UNUSED_VARIABLE(app_uart_get(&data_array[index]));
            index++;

            if ((data_array[index - 1] == '\n') ||
                (data_array[index - 1] == '\r') ||
                (index >= m_ble_nus_max_data_len))
            {
                if (index > 1)
                {
                    NRF_LOG_DEBUG("Ready to send data over BLE NUS");
                    NRF_LOG_HEXDUMP_DEBUG(data_array, index);

                    do
                    {
                        uint16_t length = (uint16_t)index;
                        err_code = ble_nus_data_send(&m_nus, data_array, &length, m_conn_handle);
                        if ((err_code != NRF_ERROR_INVALID_STATE) &&
                            (err_code != NRF_ERROR_RESOURCES) &&
                            (err_code != NRF_ERROR_NOT_FOUND))
                        {
                            APP_ERROR_CHECK(err_code);
                        }
                    } while (err_code == NRF_ERROR_RESOURCES);
                }

                index = 0;
            }
            break;

        case APP_UART_COMMUNICATION_ERROR:
            APP_ERROR_HANDLER(p_event->data.error_communication);
            break;

        case APP_UART_FIFO_ERROR:
            APP_ERROR_HANDLER(p_event->data.error_code);
            break;

        default:
            break;
    }
}
/**@snippet [Handling the data received over UART] */

What you could do is to add a timer in the ble_app_uart example that will check the status of the data_array buffer, and send it after some time even if the LF or CR characters aren't received.

Essentially, if the index variable is larger than 0 it means that some data has been buffered in the data_array buffer but not yet sent, and if it stays over 0 for a certain amount of time without anything happening you could just send the data_array buffer immediately and clear the index variable (similar to how it's already done in the uart_event_handle(..) function when CR or LF is received).

Best regards
Torbjørn

RE: send and receive data over ble without character 0xDA (Enter)

user103656 — Sun, 22 May 2022 05:13:58 GMT

Thanks Torbjørn.

Sorry but I can't understand correctly. for example if a frame(binary) send from LabView to Devkit, the DK won't receive this frame because The end of the frame does not have the character 0xDA and won't run ble_nus_chars_received_uart_print(..) function. This is my problem and I want to solve that.

Can you help me?

Best regards

MohammadAmin

RE: send and receive data over ble without character 0xDA (Enter)

user2116 — Wed, 18 May 2022 12:58:13 GMT

Hi Mohammad

This behavior is set by the ble_app_uart and ble_app_uart_c examples, and you should be able to change the application code in order to change the criteria's used to send or receive data.

For example, in the ble_app_uart_c example it is the ble_nus_chars_received_uart_print(..) function that is used to process the data received from the peer Bluetooth device and forward it to the UART interface, while the uart_event_handle(..) function is processing the UART data and sending it over the Bluetooth connection.

Best regards
Torbjørn