RE: async UART coming in broken packets

Nathan45 — Wed, 08 Nov 2023 19:55:24 GMT

Glad I could help!

God bless,

Nathan

RE: async UART coming in broken packets

Mike Austin (LPI) — Wed, 08 Nov 2023 05:05:55 GMT

Nathan45 - awesome! This is exactly what I've been trying to understand how to do, having stumbled across the same Github example. You've saved me heaps of time/hassle.

Not sure I fully understand what I'm doing, but I've got something working and so now I can play around with it and make sure I do

Cheers,

Mike

RE: async UART coming in broken packets

Nathan45 — Thu, 18 May 2023 16:27:35 GMT

For anyone with a similar issue, I found that working through the linked github example made UART work a LOT better and helped me to understand it better. In a nutshell:

- Double buffering is important! don't leave it out!

- You don't have to understand double buffering to implement it, as shown in the linked example it's just a single line of code in the UART callback, and a few lines of setting up the buffer at the top of the file.

- Message queues are important too! Those are worth understanding a bit more. I don't think they are required, but they work really well in tandem with async UART, and thats what the linked example uses.

- The linked example prints everything right away, but if you want the data in memory so you can perform operations on it you can start a thread that checks the message queue for new messages using the "k_msgq_get(...)" function. If this function returns true, it means that there is uart data ready to save to memory and you just save it and repeat basically. I added a basic snippet that I use (I modified the snippet from what we exactly use for intellectual property reasons, code may/maynot be broken but it should at least work as a starting point).

https://github.com/too1/ncs-uart-async-count-rx

#define UART0_INTERPRETER_STACKSIZE 512 //thread stuff
#define UART0_INTERPRETER_PRIORITY 7    //thread stuff

#define UART_BUF_SIZE 64

/ .
/ .
/ .

void uart_printer() {
	printk("STARTING UART GRABBER THREAD"); 
	app_uart_send("START\r\n", strlen("START\r\n"));
	int data_length;
	struct uart_msg_queue_item incoming_message;

	while (1) {
		//app_uart_send("C", 1);
		// This function will not return until a new message is ready
		if (k_msgq_get(&uart_rx_msgq, &incoming_message, K_NO_WAIT) == 0) {
			printk("message detected\n");
			uint8_t string_buffer[UART_BUF_SIZE] = "0";
			uint8_t read_value[UART_BUF_SIZE] = "0";
			uint8_t new_buffer[UART_BUF_SIZE] = "0";
			data_length = 0;

			memcpy(string_buffer, incoming_message.bytes, incoming_message.length);
			data_length += incoming_message.length;
			string_buffer[data_length] = '\0';
			// Read remaining bytes after initial read is started. append them to final string
			while (k_msgq_get(&uart_rx_msgq, &incoming_message, K_MSEC(50)) == 0) { //K_MSEC(x) time value = uart timeout sort of
				memcpy(new_buffer, incoming_message.bytes, incoming_message.length);
				//memcpy(new_buffer, "x", 1);
				data_length += incoming_message.length;
				strcat(string_buffer, new_buffer);
				string_buffer[data_length] = '\0';
			}
			printk("message grabbed\n");
			
			strncpy(read_value, string_buffer, strlen(string_buffer));
			//LOG_INF("message = %s", read_value);
			// HOORAY!! read value is now store in memory as read_value. Also as string_buffer.
			/////////////// PROCESS/HANDLE DATA BELOW //////////////////////
			
			/ .
			/ .
			/ .

			////////////////////////////////////////////////////////////////////////
		}
		k_msleep(10); //give other threads time
	}
}

/ .
/ .
/ .

K_THREAD_DEFINE(t_uart0_interpreter_id, UART0_INTERPRETER_STACKSIZE, uart_printer, NULL, NULL, NULL, UART0_INTERPRETER_PRIORITY, 0, 0);

RE: async UART coming in broken packets

Kenneth — Mon, 08 May 2023 12:42:48 GMT

Hello,

I think this for most part is "just" something you need to work through. The first I would have looked at is examples and driver test projects that use uart, but also check the documentation. For instance you are not feeding a buffer as recommended:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/hardware/peripherals/uart.html#c.uart_event_type.UART_RX_BUF_REQUEST

Here is description of handling of events:
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/hardware/peripherals/uart.html#c.uart_event_type

Kenneth