RE: Send data with BLE

Neantr — Wed, 11 Apr 2018 09:52:19 GMT

Thanks a lot for your answer, i'll try to do like this !

RE: Send data with BLE

Sigurd — Wed, 11 Apr 2018 08:11:44 GMT

Hi,

The maximum length of data (in bytes) that can be transmitted, is limited by ATT MTU - 3(header). This is by default 20, but can be negotiated higher if the phone support it. The desired ATT MTU is set to 64 in the gatt_init() function in main.c. The maximum length will therefore be 61 bytes(if the phone support it).

If you want to send more data than this, you will need to split the data up, and call ble_nus_string_send() several times. This is how it is done in the uart_event_handle() function in main.c, where the data is sent when it exceed the maximum length(m_ble_nus_max_data_len), or if a new-line character is received.

Snippet from uart_event_handle() :

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");
		NRF_LOG_HEXDUMP_DEBUG(data_array, index);

		do
		{
			uint16_t length = (uint16_t)index;
			err_code = ble_nus_string_send(&m_nus, data_array, &length);
			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;