nRF52840 UART TX in Interrupt mode

RE: nRF52840 UART TX in Interrupt mode

Susheel Nuguru — Fri, 23 Feb 2024 07:05:22 GMT

Lukas,

This looks like a bug based on the information you have provided. But unfortunately, I did not manage to get time to dig into this. We are currently a bit under staffed this week due to winter holidays (vinterferie) in Norway. I will reserve some dedicated days to test this next week. Really sorry for delays so far.

RE: nRF52840 UART TX in Interrupt mode

zazas321 — Tue, 20 Feb 2024 11:39:19 GMT

The commit that you have linked is a different branch (only for testing/receiving messages via the UART0) and that works fine since its quite straight forward.

Please look at UART0_UART1_Interrupt which is a different branch.

I still have not yet managed to get the UART1 working properly (see the logs above, I am only able to receive part of the message). I will connect the logic analyzer to monitor RX/TX lines

UPDATE

After monitoring the RX/TX lines using logic analyzer everything seems fine:

I am currently debugging to figure out what could be the issue with the UART1 receive:

I have found a very simillar post (Limited to reading 8 bytes per transmission on uart_fifo_read() Function ) but it does not seem to be solved.

Could it be that there is an issue with using uart_fifo_read ?

I have tested it with different length data. For example, if I try to send 4 bytes:

uart_irq_tx(dev_uart1, "Hel\n", 4);

Everything seems fine:

[00:01:45.050,109] [1B][0m<inf> nrf52_learning: tx_sent: 4[1B][0m
[00:01:45.070,495] [1B][0m<inf> nrf52_learning: Data to be sent length = 4[1B][0m
[00:01:45.092,285] [1B][0m<inf> nrf52_learning: UART1 data transmitted
[1B][0m
[00:01:45.113,830] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:01:45.135,192] [1B][0m<inf> nrf52_learning: UART1 data received: H
[1B][0m
[00:01:45.156,738] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:01:45.178,131] [1B][0m<inf> nrf52_learning: UART1 data received: e
[1B][0m
[00:01:45.199,676] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:01:45.221,038] [1B][0m<inf> nrf52_learning: UART1 data received: l
[1B][0m
[00:01:45.242,584] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:01:45.263,946] [1B][0m<inf> nrf52_learning: UART1 data received: 

[1B][0m
[00:01:45.285,461] [1B][0m<inf> nrf52_learning: UART1_RX(4): Hel

However, anything above 7 bytes will not be properly received:

*** Booting nRF Connect SDK v2.5.1 ***
[00:00:05.364,227] [1B][0m<inf> nrf52_learning: tx_sent: 9[1B][0m
[00:00:05.369,720] [1B][0m<inf> nrf52_learning: Data to be sent length = 9[1B][0m
[00:00:05.376,617] [1B][0m<inf> nrf52_learning: UART1 data transmitted
[1B][0m
[00:00:05.383,270] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.389,739] [1B][0m<inf> nrf52_learning: UART1 data received: H
[1B][0m
[00:00:05.396,392] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.402,832] [1B][0m<inf> nrf52_learning: UART1 data received: e
[1B][0m
[00:00:05.409,484] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.415,954] [1B][0m<inf> nrf52_learning: UART1 data received: l
[1B][0m
[00:00:05.422,607] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.429,077] [1B][0m<inf> nrf52_learning: UART1 data received: l
[1B][0m
[00:00:05.435,729] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.442,199] [1B][0m<inf> nrf52_learning: UART1 data received: o
[1B][0m
[00:00:05.448,852] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.470,214] [1B][0m<inf> nrf52_learning: UART1 data received: 1
[1B][0m
[00:00:05.491,760] [1B][0m<inf> nrf52_learning: uart_fifo_read len: 1[1B][0m
[00:00:05.513,122] [1B][0m<inf> nrf52_learning: UART1 data received: 2
[1B][0m

I would really appreciate if you could take a look at this. Perhaps this is a bug ?

RE: nRF52840 UART TX in Interrupt mode

Susheel Nuguru — Tue, 20 Feb 2024 10:08:52 GMT

[quote user="zazas321"]As you can see from the code above, I have put tx and rx handlers into a single function (uart1_irq_handler). Previously I had 2 different interrupt handlers which is probably not correct.[/quote]

Thanks for the info. Yes having two callbacks is not the right way to do it.

I have looked into the last commit you made and it looks neat and correct. Thanks for posting the code here which will be helpful to others aswell :)

RE: nRF52840 UART TX in Interrupt mode

zazas321 — Tue, 20 Feb 2024 09:24:11 GMT

Hello. I have made some progress regarding this. I have made some changes in the code and uploaded latest code to the project in the github repository I have linked previously.

The full code:

/*
 * Copyright (c) 2012-2014 Wind River Systems, Inc.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <zephyr/kernel.h>
#include "stdio.h"
#include "zephyr/drivers/uart.h"
#define LOG_LEVEL 4
#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(nrf52_learning);

static const struct device *dev_uart0;
static const struct device *dev_uart1;

static void app_uart0_init();
static void uart0_irq_handler(const struct device *dev, void *context);

static void app_uart1_init();
static void uart1_irq_handler(const struct device *dev, void *context);

static K_SEM_DEFINE(tx_sem, 0, 1); // Semaphore to signal UART data transmitted

static uint8_t *tx_data;
static size_t tx_data_length;

#define RX_BUF_SIZE 64

static void app_uart0_init()
{
	dev_uart0 = DEVICE_DT_GET(DT_NODELABEL(uart0));
	if (!device_is_ready(dev_uart0))
	{
		return;
	}

	uart_irq_callback_set(dev_uart0, uart0_irq_handler);
	uart_irq_rx_enable(dev_uart0);
}

static void uart0_irq_handler(const struct device *dev, void *context)
{
	uint8_t char_received;
	static uint8_t command_line[RX_BUF_SIZE];
	static int char_counter = 0;

	while (uart_irq_update(dev) && uart_irq_is_pending(dev))
	{
		if (uart_irq_rx_ready(dev))
		{
			int len = uart_fifo_read(dev, &char_received, 1);
			if (len)
			{
				command_line[char_counter] = char_received;
				char_counter++;
				if (char_received == '\n' || char_received == '\r')
				{
					command_line[char_counter] = '\0'; // put null at the end of the string to indicate end of message or end of string			   // reset the char counter
					LOG_INF("UART0_RX(%u): %s \n", char_counter, command_line);
					char_counter = 0;
					memset(&command_line, 0, sizeof(command_line));
				}
			}
		}
	}
}

// Initialize UART1
static void app_uart1_init()
{
	dev_uart1 = DEVICE_DT_GET(DT_NODELABEL(uart1));
	if (!device_is_ready(dev_uart1))
	{
		printk("UART1 is not ready \n");
		return;
	}
	uart_irq_rx_disable(dev_uart1);
	uart_irq_tx_disable(dev_uart1);

	uart_irq_callback_set(dev_uart1, uart1_irq_handler);
	uart_irq_rx_enable(dev_uart1);
}


static void uart1_irq_handler(const struct device *dev, void *context)
{
	uint8_t char_received;
	static uint8_t command_line[RX_BUF_SIZE];
	static int char_counter = 0;

	if (!(uart_irq_rx_ready(dev) || uart_irq_tx_ready(dev)))
	{
		LOG_DBG("spurious interrupt");
	}

	if (uart_irq_tx_ready(dev))
	{
		int tx_sent = uart_fifo_fill(dev, (uint8_t *)tx_data, tx_data_length);

		if (tx_sent <= 0)
		{
			LOG_ERR("Error %d sending data over UART1 bus\n", tx_sent);
			return;
		}

		while (uart_irq_tx_complete(dev) != 1)
		{
			LOG_INF("Wait for UART1 data transmition complete\n");
		}
		LOG_INF("UART1 data transmitted\n");
		uart_irq_tx_disable(dev);
		k_sem_give(&tx_sem);
	}

	if (uart_irq_rx_ready(dev))
	{
		int len = uart_fifo_read(dev, &char_received, 1);
		if (len)
		{
			LOG_INF("UART1 data received: %c\n", char_received);
			command_line[char_counter] = char_received;
			char_counter++;
			if (char_received == '\n' || char_received == '\r')
			{
				command_line[char_counter] = '\0'; // put null at the end of the string to indicate end of message or end of string
				LOG_INF("UART1_RX(%u): %s \n", char_counter, command_line);
				char_counter = 0; // reset the char counter

				memset(&command_line, 0, sizeof(command_line));
			}
		}
	}
}


int uart_irq_tx(const struct device *dev, const uint8_t *buf, size_t len)
{
	tx_data = buf;
	tx_data_length = len;
	uart_irq_tx_enable(dev);
	k_sem_take(&tx_sem, K_FOREVER);
	return len;
}

int main(void)
{
	app_uart0_init();
	app_uart1_init();
	while (1)
	{
		k_msleep(5000);
		uart_irq_tx(dev_uart1, "Hello from UART1\n", 17);
	}
}

As you can see from the code above, I have put tx and rx handlers into a single function (uart1_irq_handler). Previously I had 2 different interrupt handlers which is probably not correct.

I can now short 2 UART1 pins together and I will be able to receive part of the message. See the serial temrinal logs below:

I have send 17 bytes as shown below:

	while (1)
	{
		k_msleep(5000);
		uart_irq_tx(dev_uart1, "Hello from UART1\n", 17);
	}

But only received 7 bytes. I am happy that I have managed and currently working on solving this issue. Perhaps you will have some insights :)

RE: nRF52840 UART TX in Interrupt mode

zazas321 — Mon, 19 Feb 2024 13:21:30 GMT

Thanks for looking at this.

I would suggest you try this project. This is the project that I work on and thats where I posted the code snippets from
https://github.com/krupis/nrf52_learning/tree/uart0_uart1_interrupt

You can easily flash this to nRF52540DK to check UART0 and UART1 yourself and it will become clear to you what is the problem that I am trying to solve.

What I want to achieve is very simple:

I want to get the UART1 and UART0 working properly (receive and transmit) in interrupt mode.

UART0 I use for logging and sending custom commands the device

UART1 I plan to connect to an external device and I need to be able to receive/transmit various length messages but as I shown above currently I cannot get the transmit/receive to work properly on UART1 :)

For some reason, I am convinced that the issue lies within incorrect implementation of uart1_irq_transmit_handler becuase I could not find any proper sample projects where it has been shown how to correctly transmit data over the UART in interrupt mode.

RE: nRF52840 UART TX in Interrupt mode

Susheel Nuguru — Mon, 19 Feb 2024 06:21:10 GMT

Hi Lukas,

I tried your code snippet with some changes. I also do not know what is the use of tx_data_idx.The code does not look very optimal. This does not seem to be production quality. Unfortunately we do not seem to have any dedicated sample that is using the peripheral in interrupt mode apart from what is being used with other features like ble_hci_uart.Most of them are using UART0 as the interrupt driven port and they seems to be working. I have not tested changing them to use uart1 port instead of uart0.

There is some issue in the code and shorting the TX/RX pin like you said break the flow like you mentioned.

I need to find more time to test this as the code you mentioned is not official from us (hence I cannot create any internal ticket to allocate time immediately)

RE: nRF52840 UART TX in Interrupt mode

zazas321 — Mon, 12 Feb 2024 08:44:30 GMT

Any updates regarding interrupt UART yet?

RE: nRF52840 UART TX in Interrupt mode

zazas321 — Thu, 08 Feb 2024 14:07:10 GMT

Im not that interested in the code snippet from that post I linked.

I simply want to know what is the best/most optimal way to setup uart interrupt mode to be able to send and receive data.

That post just happen to be somewhat I can use as a starting point. Since I could not find any other official nordic samples for interrupt uart data reception

If that would be easier for you, we can simply ignore that post and look at it from scratch - how to setup uart interrupt transmit and receive handlers

RE: nRF52840 UART TX in Interrupt mode

Susheel Nuguru — Thu, 08 Feb 2024 13:52:42 GMT

Hi Lukas,

Vidar does not remember specifics of the case that you linked in your initial question. And I do not know the context of those threads. I cannot answer specifically why those code snippets have that logic when it comes from outside Nordic solutions. I was hoping that Vidar who was looking at the other thread have some context but he does not.

Where did you get this code snippet from? Can't you ask these questions in that same post as this is relevant to those threads?

RE: nRF52840 UART TX in Interrupt mode

zazas321 — Wed, 07 Feb 2024 08:23:36 GMT

Hey :) Any feedback available as I still have not yet managed to figure out

RE: nRF52840 UART TX in Interrupt mode

Susheel Nuguru — Fri, 02 Feb 2024 13:04:37 GMT

Hei Lukas,

I did not manage to look into this today, but I will ask my colleague Vidar who is an expert in such things to see if he has any insights for this.