Problems with the length of GATT Charactersitic in BLE_p2pServer_ota example

[ledi001]

Hello,

here in my code I want to send the received values of the payload directly to USART2. This works fine if I send less than 20 characters. If I send more, the program chrashed.

case P2P_SERVER_UART_C_WRITE_NO_RESP_EVT:
      /* USER CODE BEGIN Service1Char3_WRITE_NO_RESP_EVT */
    	uint16_t payload_Length = p_Notification->DataTransfered.Length;	// conversion uint8 Length to uint16 payload_Length
    	if(HAL_UART_Transmit_DMA(&huart2, p_Notification->DataTransfered.p_Payload, payload_Length) != HAL_OK)
		{
			Error_Handler();
		}

When I set a breakpoint and check the value of the length, a maximum value of 20 is displayed although the variable SizeUart_C = 50 (in file p2p_server.c).

Why is this the case?
What can I do to transfer more characters?

[ledi001]

I would like to provide more information on this topic here.

In cubeMX i have set the length of the value to 30 and the length of the "Value length" to Variable because i also want to send less than 30 characters.

Then I checked the variable "SizeUart_C" in the file p2p_server_app.c , which has the value 30.

In my opinion, the problem must lie in this program line:

uint16_t payload_Length = p_Notification->DataTransfered.Length;

However, I cannot understand why the value of “Length” does not become > 20. If I send 19 characters, the value in "payload_Length" is 19, but if I send 22 characters or more, the value here is 20.

[STTwo-32]

Hello @ledi001 

I suggest you take a look at the chapter 8.6.9 of the AN5289. It explains how you can maximize the data throughput.

Best Regards.

STTwo-32