Fixed length uart frame detect on Zephyr

RE: Fixed length uart frame detect on Zephyr

P_WE — Wed, 01 Nov 2023 07:56:14 GMT

Very usefull thread. I've got solution of my problem. Thanks.

RE: Fixed length uart frame detect on Zephyr

Einar Thorsrud — Mon, 30 Oct 2023 11:40:22 GMT

I see. The unofficial sample you have based this on is not optimal, in the sense that it does not use double buffering. You should use double buffering, and it also makes sense to use large buffers (to avoid having too swap buffers too often). The last posts in this thread describe this.

RE: Fixed length uart frame detect on Zephyr

P_WE — Sat, 28 Oct 2023 17:53:47 GMT

My mistake, of course it is 115200. I didn't notice issue when baudrate is slower. The problem is that last byte is in the buffer, but it is not read by:

k_msgq_get(&uart_rx_msgq, &incoming_message, K_FOREVER);

It is read when next frame has come.

Frame has 20B length, buffer is 16B long.

Situation is explained on screens.

UART0 is read in separate thread. There is also BLE scanner active in one time.

Regads,

P_WE

RE: Fixed length uart frame detect on Zephyr

Einar Thorsrud — Fri, 27 Oct 2023 13:54:16 GMT

Hi,

Do you mean 115200 baud? Is it so that you don't see this issue with lower baud rates?

RE: Fixed length uart frame detect on Zephyr

P_WE — Fri, 27 Oct 2023 11:43:51 GMT

I used this code: https://github.com/too1/ncs-uart-async-count-rx which is linked in another subject. It's OK, beacause I get data lenght and data in buffer but unfortunetelly it doesn't work well with 11520 baud. It's often lose one byte. I read data in seperate thread.

void thread_serial_central(void)
{
	uart0_init();
	LOG_INF("UART0 started");
	struct uart_msg_queue_item incoming_message;

	while(1)
	{
		// This function will not return until a new message is ready
		k_msgq_get(&uart_rx_msgq, &incoming_message, K_FOREVER);
		
		static uint8_t string_buffer[UART_BUF_SIZE + 1];
		memcpy(string_buffer, incoming_message.bytes, incoming_message.length);
		string_buffer[incoming_message.length] = 0;
		
		LOG_INF("RX %i: %s\n", incoming_message.length, string_buffer);
	}
}

Regards,

P_WE

RE: Fixed length uart frame detect on Zephyr

Einar Thorsrud — Mon, 23 Oct 2023 11:43:21 GMT

Hi,

It is not entierly clear to me what you receive and what you expect to receive? Can you show some examples and explain in more detail?

Generally though, if you are looking for a specific pattern, I would consider keeping a buffer where you store incoming data and search for the full "packet" there, so that it does not matter if you first receive a part of it, and subsequently the last part.