In the UART interrupt, I am entering the error_isr, and the UART_RX_STOPPED state is causing me to fail to receive data.

[dcjin]

I am using nRF Connect SDK v2.1.0 in the Toolchain Manager of nRF Connect for Desktop.

The UART data is sent from PC to the board.

I am using the nRF52833 chip, and I believe it is unlikely to be a hardware issue because UART reception works fine in other versions.

The board is unable to receive all the data and only receives a portion of it. The data that is not received enters the UART_RX_STOPPED state in the error_isr.

Even after disabling both Bluetooth Beacon and ESB, when attempting to use UART, I still encounter the error_isr.

I am unable to determine the reason for entering the error_isr.

static void error_isr(const struct device *dev)
{
	if (uart0_cb.rx_timeout != SYS_FOREVER_US) {
		k_timer_stop(&uart0_cb.rx_timeout_timer);
	}
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_ERROR);

	if (!uart0_cb.rx_enabled) {
		nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPRX);
	}
	struct uart_event event = {
		.type = UART_RX_STOPPED,											// ERROR CODE OCCURED 2023 05 25
		.data.rx_stop.reason =
			UART_ERROR_FROM_MASK(
				nrf_uart_errorsrc_get_and_clear(uart0_addr)),
		.data.rx_stop.data.len = uart0_cb.rx_counter
					 - uart0_cb.rx_offset,
		.data.rx_stop.data.offset = uart0_cb.rx_offset,
		.data.rx_stop.data.buf = uart0_cb.rx_buffer
	};

	user_callback(dev, &event);
	/* Abort transfer. */
	// uart_nrfx_rx_disable(dev);
}



void uart_nrfx_isr(const struct device *uart)
{
	if (nrf_uart_int_enable_check(uart0_addr, NRF_UART_INT_MASK_ERROR) &&
	    nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_ERROR)) {
		error_isr(uart);
	} else if (nrf_uart_int_enable_check(uart0_addr,
					     NRF_UART_INT_MASK_RXDRDY) &&
		   nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXDRDY)) {
		rx_isr(uart);
	}

	if (nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_TXDRDY)
	    && nrf_uart_int_enable_check(uart0_addr,
					 NRF_UART_INT_MASK_TXDRDY)) {
		tx_isr(uart);
	}

	if (nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXTO)) {
		rxto_isr(uart);
	}
}

Do you need any more additional information?

[Håkon Alseth]

Here is the hardware wise sources for the ERRORSRC:

https://infocenter.nordicsemi.com/topic/ps_nrf52833/uarte.html?cp=5_1_0_5_31_8_20#register.ERRORSRC

 

When one of these occurs, the zephyr uart driver will automatically stop the UART peripheral (you can manually restart it afterwards). Framing error is typical is if the baudrate between the receiver and sender has a mismatch, especially over larger transfers.

It is therefore important that you use the external hfclk as the source, to ensure that the uart baudrate is as close to the ideal baudrate as possible.

 

Kind regards,

Håkon

[dcjin]

I still encounter the same error even when using hlclk.

I want to receive 21 bytes without any errors.

Is there no way?

[Håkon Alseth]

Hi,

 

Could you share how you setup the UART RX in the application space?

 

Kind regards,

Håkon

[dcjin]

In an overlay file, pin configuration is performed for setting up the pins.

Fullscreen uart_nrfx_uart.c Download

/*
 * Copyright (c) 2016-2019 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/**
 * @brief Driver for Nordic Semiconductor nRF5X UART
 */

#include <zephyr/drivers/uart.h>
#include <zephyr/pm/device.h>
#include <soc.h>
#include <hal/nrf_uart.h>

#ifdef CONFIG_PINCTRL
#include <zephyr/drivers/pinctrl.h>
#else
#include <hal/nrf_gpio.h>
#endif /* CONFIG_PINCTRL */

/*
 * Extract information from devicetree.
 *
 * This driver only supports one instance of this IP block, so the
 * instance number is always 0.
 */
#define DT_DRV_COMPAT	nordic_nrf_uart

#define PROP(prop)	DT_INST_PROP(0, prop)
#define HAS_PROP(prop)	DT_INST_NODE_HAS_PROP(0, prop)

#define BAUDRATE	PROP(current_speed)

#ifdef CONFIG_PINCTRL
#define DISABLE_RX	PROP(disable_rx)
#else
#define DISABLE_RX	!HAS_PROP(rx_pin)
#endif /* CONFIG_PINCTRL */
#define HW_FLOW_CONTROL_AVAILABLE	PROP(hw_flow_control)

#define IRQN		DT_INST_IRQN(0)
#define IRQ_PRIO	DT_INST_IRQ(0, priority)

static NRF_UART_Type *const uart0_addr = (NRF_UART_Type *)DT_INST_REG_ADDR(0);

struct uart_nrfx_config {
#ifdef CONFIG_PINCTRL
	const struct pinctrl_dev_config *pcfg;
#else
	uint32_t tx_pin;
	uint32_t rx_pin;
	uint32_t rts_pin;
	uint32_t cts_pin;
	bool rx_pull_up;
	bool cts_pull_up;
#endif /* CONFIG_PINCTRL */
};

/* Device data structure */
struct uart_nrfx_data {
	struct uart_config uart_config;
};

#ifdef CONFIG_UART_0_ASYNC
static struct {
	uart_callback_t callback;
	void *user_data;

	uint8_t *rx_buffer;
	uint8_t *rx_secondary_buffer;
	size_t rx_buffer_length;
	size_t rx_secondary_buffer_length;
	volatile size_t rx_counter;
	volatile size_t rx_offset;
	int32_t rx_timeout;
	struct k_timer rx_timeout_timer;
	bool rx_enabled;

	bool tx_abort;
	const uint8_t *volatile tx_buffer;
	/* note: this is aliased with atomic_t in uart_nrfx_poll_out() */
	unsigned long tx_buffer_length;
	volatile size_t tx_counter;
#if HW_FLOW_CONTROL_AVAILABLE
	int32_t tx_timeout;
	struct k_timer tx_timeout_timer;
#endif
} uart0_cb;
#endif /* CONFIG_UART_0_ASYNC */

#ifdef CONFIG_UART_0_INTERRUPT_DRIVEN

static uart_irq_callback_user_data_t irq_callback; /**< Callback function pointer */
static void *irq_cb_data; /**< Callback function arg */

/* Variable used to override the state of the TXDRDY event in the initial state
 * of the driver. This event is not set by the hardware until a first byte is
 * sent, and we want to use it as an indication if the transmitter is ready
 * to accept a new byte.
 */
static volatile uint8_t uart_sw_event_txdrdy;
static volatile bool disable_tx_irq;

#endif /* CONFIG_UART_0_INTERRUPT_DRIVEN */

#ifndef CONFIG_PINCTRL
static void uart_nrfx_pins_configure(const struct device *dev, bool sleep)
{
	const struct uart_nrfx_config *cfg = dev->config;

	if (!sleep) {
		if (cfg->tx_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_pin_write(cfg->tx_pin, 1);
			nrf_gpio_cfg_output(cfg->tx_pin);
		}

		if (cfg->rx_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_cfg_input(cfg->rx_pin,
					   (cfg->rx_pull_up ?
					    NRF_GPIO_PIN_PULLUP :
					    NRF_GPIO_PIN_NOPULL));
		}

		if (cfg->rts_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_pin_write(cfg->rts_pin, 1);
			nrf_gpio_cfg_output(cfg->rts_pin);
		}

		if (cfg->cts_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_cfg_input(cfg->cts_pin,
					   (cfg->cts_pull_up ?
					    NRF_GPIO_PIN_PULLUP :
					    NRF_GPIO_PIN_NOPULL));
		}
	} else {
		if (cfg->tx_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_cfg_default(cfg->tx_pin);
		}

		if (cfg->rx_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_cfg_default(cfg->rx_pin);
		}

		if (cfg->rts_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_cfg_default(cfg->rts_pin);
		}

		if (cfg->cts_pin != NRF_UART_PSEL_DISCONNECTED) {
			nrf_gpio_cfg_default(cfg->cts_pin);
		}
	}

	nrf_uart_txrx_pins_set(uart0_addr, cfg->tx_pin, cfg->rx_pin);
	nrf_uart_hwfc_pins_set(uart0_addr, cfg->rts_pin, cfg->cts_pin);
}
#endif /* !CONFIG_PINCTRL */

static bool event_txdrdy_check(void)
{
	return (nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_TXDRDY)
#ifdef CONFIG_UART_0_INTERRUPT_DRIVEN
		|| uart_sw_event_txdrdy
#endif
	       );
}

static void event_txdrdy_clear(void)
{
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_TXDRDY);
#ifdef CONFIG_UART_0_INTERRUPT_DRIVEN
	uart_sw_event_txdrdy = 0U;
#endif
}


/**
 * @brief Set the baud rate
 *
 * This routine set the given baud rate for the UART.
 *
 * @param dev UART device struct
 * @param baudrate Baud rate
 *
 * @retval 0 on success.
 * @retval -EINVAL for invalid baudrate.
 */

static int baudrate_set(const struct device *dev, uint32_t baudrate)
{
	nrf_uart_baudrate_t nrf_baudrate; /* calculated baudrate divisor */

	switch (baudrate) {
	case 300:
		/* value not supported by Nordic HAL */
		nrf_baudrate = 0x00014000;
		break;
	case 600:
		/* value not supported by Nordic HAL */
		nrf_baudrate = 0x00027000;
		break;
	case 1200:
		nrf_baudrate = NRF_UART_BAUDRATE_1200;
		break;
	case 2400:
		nrf_baudrate = NRF_UART_BAUDRATE_2400;
		break;
	case 4800:
		nrf_baudrate = NRF_UART_BAUDRATE_4800;
		break;
	case 9600:
		nrf_baudrate = NRF_UART_BAUDRATE_9600;
		break;
	case 14400:
		nrf_baudrate = NRF_UART_BAUDRATE_14400;
		break;
	case 19200:
		nrf_baudrate = NRF_UART_BAUDRATE_19200;
		break;
	case 28800:
		nrf_baudrate = NRF_UART_BAUDRATE_28800;
		break;
	case 31250:
		nrf_baudrate = NRF_UART_BAUDRATE_31250;
		break;
	case 38400:
		nrf_baudrate = NRF_UART_BAUDRATE_38400;
		break;
	case 56000:
		nrf_baudrate = NRF_UART_BAUDRATE_56000;
		break;
	case 57600:
		nrf_baudrate = NRF_UART_BAUDRATE_57600;
		break;
	case 76800:
		nrf_baudrate = NRF_UART_BAUDRATE_76800;
		break;
	case 115200:
		nrf_baudrate = NRF_UART_BAUDRATE_115200;
		break;
	case 230400:
		nrf_baudrate = NRF_UART_BAUDRATE_230400;
		break;
	case 250000:
		nrf_baudrate = NRF_UART_BAUDRATE_250000;
		break;
	case 460800:
		nrf_baudrate = NRF_UART_BAUDRATE_460800;
		break;
	case 921600:
		nrf_baudrate = NRF_UART_BAUDRATE_921600;
		break;
	case 1000000:
		nrf_baudrate = NRF_UART_BAUDRATE_1000000;
		break;
	default:
		return -EINVAL;
	}

	nrf_uart_baudrate_set(uart0_addr, nrf_baudrate);

	return 0;
}

/**
 * @brief Poll the device for input.
 *
 * @param dev UART device struct
 * @param c Pointer to character
 *
 * @return 0 if a character arrived, -1 if the input buffer if empty.
 */

static int uart_nrfx_poll_in(const struct device *dev, unsigned char *c)
{
	if (!nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXDRDY)) {
		return -1;
	}

	/* Clear the interrupt */
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXDRDY);

	/* got a character */
	*c = nrf_uart_rxd_get(uart0_addr);

	return 0;
}

#ifdef CONFIG_UART_0_ASYNC
static void uart_nrfx_isr(const struct device *dev);
#endif

/**
 * @brief Output a character in polled mode.
 *
 * @param dev UART device struct
 * @param c Character to send
 */
static void uart_nrfx_poll_out(const struct device *dev, unsigned char c)
{
	atomic_t *lock;
#ifdef CONFIG_UART_0_ASYNC
	while (uart0_cb.tx_buffer) {
		/* If there is ongoing asynchronous transmission, and we are in
		 * ISR, then call uart interrupt routine, otherwise
		 * busy wait until transmission is finished.
		 */
		if (k_is_in_isr()) {
			uart_nrfx_isr(dev);
		}
	}
	/* Use tx_buffer_length as lock, this way uart_nrfx_tx will
	 * return -EBUSY during poll_out.
	 */
	lock = &uart0_cb.tx_buffer_length;
#else
	static atomic_val_t poll_out_lock;

	lock = &poll_out_lock;
#endif

	if (!k_is_in_isr()) {
		uint8_t safety_cnt = 100;

		while (atomic_cas((atomic_t *) lock,
				  (atomic_val_t) 0,
				  (atomic_val_t) 1) == false) {
			if (IS_ENABLED(CONFIG_MULTITHREADING)) {
				/* k_sleep allows other threads to execute and finish
				 * their transactions.
				 */
				k_msleep(1);
			} else {
				k_busy_wait(1000);
			}
			if (--safety_cnt == 0) {
				break;
			}
		}
	} else {
		*lock = 1;
	}
	/* Reset the transmitter ready state. */
	event_txdrdy_clear();

	/* Activate the transmitter. */
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STARTTX);

	/* Send the provided character. */
	nrf_uart_txd_set(uart0_addr, (uint8_t)c);

	/* Wait until the transmitter is ready, i.e. the character is sent. */
	int res;

	NRFX_WAIT_FOR(event_txdrdy_check(), 1000, 1, res);

	/* Deactivate the transmitter so that it does not needlessly
	 * consume power.
	 */
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPTX);

	/* Release the lock. */
	*lock = 0;
}

/** Console I/O function */
static int uart_nrfx_err_check(const struct device *dev)
{
	/* register bitfields maps to the defines in uart.h */
	return nrf_uart_errorsrc_get_and_clear(uart0_addr);
}

static int uart_nrfx_configure(const struct device *dev,
			       const struct uart_config *cfg)
{
	struct uart_nrfx_data *data = dev->data;
	nrf_uart_config_t uart_cfg;

#if defined(UART_CONFIG_STOP_Msk)
	switch (cfg->stop_bits) {
	case UART_CFG_STOP_BITS_1:
		uart_cfg.stop = NRF_UART_STOP_ONE;
		break;
	case UART_CFG_STOP_BITS_2:
		uart_cfg.stop = NRF_UART_STOP_TWO;
		break;
	default:
		return -ENOTSUP;
	}
#else
	if (cfg->stop_bits != UART_CFG_STOP_BITS_1) {
		return -ENOTSUP;
	}
#endif

	if (cfg->data_bits != UART_CFG_DATA_BITS_8) {
		return -ENOTSUP;
	}

	switch (cfg->flow_ctrl) {
	case UART_CFG_FLOW_CTRL_NONE:
		uart_cfg.hwfc = NRF_UART_HWFC_DISABLED;
		break;
	case UART_CFG_FLOW_CTRL_RTS_CTS:
		if (HW_FLOW_CONTROL_AVAILABLE) {
			uart_cfg.hwfc = NRF_UART_HWFC_ENABLED;
		} else {
			return -ENOTSUP;
		}
		break;
	default:
		return -ENOTSUP;
	}

#if defined(UART_CONFIG_PARITYTYPE_Msk)
	uart_cfg.paritytype = NRF_UART_PARITYTYPE_EVEN;
#endif
	switch (cfg->parity) {
	case UART_CFG_PARITY_NONE:
		uart_cfg.parity = NRF_UART_PARITY_EXCLUDED;
		break;
	case UART_CFG_PARITY_EVEN:
		uart_cfg.parity = NRF_UART_PARITY_INCLUDED;
		break;
#if defined(UART_CONFIG_PARITYTYPE_Msk)
	case UART_CFG_PARITY_ODD:
		uart_cfg.parity = NRF_UART_PARITY_INCLUDED;
		uart_cfg.paritytype = NRF_UART_PARITYTYPE_ODD;
		break;
#endif
	default:
		return -ENOTSUP;
	}

	if (baudrate_set(dev, cfg->baudrate) != 0) {
		return -ENOTSUP;
	}

	nrf_uart_configure(uart0_addr, &uart_cfg);

	data->uart_config = *cfg;

	return 0;
}

#ifdef CONFIG_UART_USE_RUNTIME_CONFIGURE
static int uart_nrfx_config_get(const struct device *dev,
				struct uart_config *cfg)
{
	struct uart_nrfx_data *data = dev->data;

	*cfg = data->uart_config;
	return 0;
}
#endif /* CONFIG_UART_USE_RUNTIME_CONFIGURE */

#ifdef CONFIG_UART_0_ASYNC

static void user_callback(const struct device *dev, struct uart_event *event)
{
	if (uart0_cb.callback) {
		uart0_cb.callback(dev, event, uart0_cb.user_data);
	}
}

static int uart_nrfx_callback_set(const struct device *dev,
				  uart_callback_t callback,
				  void *user_data)
{
	uart0_cb.callback = callback;
	uart0_cb.user_data = user_data;

	return 0;
}

static int uart_nrfx_tx(const struct device *dev, const uint8_t *buf,
			size_t len,
			int32_t timeout)
{
	if (atomic_cas((atomic_t *) &uart0_cb.tx_buffer_length,
		       (atomic_val_t) 0,
		       (atomic_val_t) len) == false) {
		return -EBUSY;
	}

	uart0_cb.tx_buffer = buf;
#if	HW_FLOW_CONTROL_AVAILABLE
	uart0_cb.tx_timeout = timeout;
#endif
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_TXDRDY);
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STARTTX);
	nrf_uart_int_enable(uart0_addr, NRF_UART_INT_MASK_TXDRDY);

	uint8_t txd = uart0_cb.tx_buffer[uart0_cb.tx_counter];

	nrf_uart_txd_set(uart0_addr, txd);

	return 0;
}

static int uart_nrfx_tx_abort(const struct device *dev)
{
	if (uart0_cb.tx_buffer_length == 0) {
		return -EINVAL;
	}
#if	HW_FLOW_CONTROL_AVAILABLE
	if (uart0_cb.tx_timeout != SYS_FOREVER_US) {
		k_timer_stop(&uart0_cb.tx_timeout_timer);
	}
#endif
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPTX);

	struct uart_event evt = {
		.type = UART_TX_ABORTED,
		.data.tx.buf = uart0_cb.tx_buffer,
		.data.tx.len = uart0_cb.tx_counter
	};

	uart0_cb.tx_buffer_length = 0;
	uart0_cb.tx_counter = 0;

	user_callback(dev, &evt);

	return 0;
}

static int uart_nrfx_rx_enable(const struct device *dev, uint8_t *buf,
			       size_t len,
			       int32_t timeout)
{
	if (DISABLE_RX) {
		__ASSERT(false, "TX only UART instance");
		return -ENOTSUP;
	}

	if (uart0_cb.rx_buffer_length != 0) {
		return -EBUSY;
	}

	uart0_cb.rx_enabled = 1;
	uart0_cb.rx_buffer = buf;
	uart0_cb.rx_buffer_length = len;
	uart0_cb.rx_counter = 0;
	uart0_cb.rx_secondary_buffer_length = 0;
	uart0_cb.rx_timeout = timeout;

	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_ERROR);
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXDRDY);
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXTO);
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STARTRX);
	nrf_uart_int_enable(uart0_addr, NRF_UART_INT_MASK_RXDRDY |
					NRF_UART_INT_MASK_ERROR |
					NRF_UART_INT_MASK_RXTO);

	return 0;
}

static int uart_nrfx_rx_buf_rsp(const struct device *dev, uint8_t *buf,
				size_t len)
{
	int err;
	unsigned int key = irq_lock();

	if (!uart0_cb.rx_enabled) {
		err = -EACCES;
	} else if (uart0_cb.rx_secondary_buffer_length != 0) {
		err = -EBUSY;
	} else {
		uart0_cb.rx_secondary_buffer = buf;
		uart0_cb.rx_secondary_buffer_length = len;
		err = 0;
	}

	irq_unlock(key);

	return err;
}

static int uart_nrfx_rx_disable(const struct device *dev)
{
	if (uart0_cb.rx_buffer_length == 0) {
		return -EFAULT;
	}

	uart0_cb.rx_enabled = 0;
	if (uart0_cb.rx_timeout != SYS_FOREVER_US) {
		k_timer_stop(&uart0_cb.rx_timeout_timer);
	}
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPRX);

	return 0;
}

static void rx_rdy_evt(const struct device *dev)
{
	struct uart_event event;
	size_t rx_cnt = uart0_cb.rx_counter;

	event.type = UART_RX_RDY;
	event.data.rx.buf = uart0_cb.rx_buffer;
	event.data.rx.len = rx_cnt - uart0_cb.rx_offset;
	event.data.rx.offset = uart0_cb.rx_offset;

	uart0_cb.rx_offset = rx_cnt;

	user_callback(dev, &event);
}

static void buf_released_evt(const struct device *dev)
{
	struct uart_event event = {
		.type = UART_RX_BUF_RELEASED,
		.data.rx_buf.buf = uart0_cb.rx_buffer
	};
	user_callback(dev, &event);
}

static void rx_disabled_evt(const struct device *dev)
{
	struct uart_event event = {
		.type = UART_RX_DISABLED
	};
	user_callback(dev, &event);
}

static void rx_reset_state(void)
{
	nrf_uart_int_disable(uart0_addr,
			     NRF_UART_INT_MASK_RXDRDY |
			     NRF_UART_INT_MASK_ERROR |
			     NRF_UART_INT_MASK_RXTO);
	uart0_cb.rx_buffer_length = 0;
	uart0_cb.rx_enabled = 0;
	uart0_cb.rx_counter = 0;
	uart0_cb.rx_offset = 0;
	uart0_cb.rx_secondary_buffer_length = 0;
}

static void rx_isr(const struct device *dev)
{
	struct uart_event event;

	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXDRDY);

	if (!uart0_cb.rx_buffer_length || !uart0_cb.rx_enabled) {
		/* Byte received when receiving is disabled - data lost. */
		nrf_uart_rxd_get(uart0_addr);
	} else {
		if (uart0_cb.rx_counter == 0) {
			event.type = UART_RX_BUF_REQUEST;
			user_callback(dev, &event);
		}
		uart0_cb.rx_buffer[uart0_cb.rx_counter] =
			nrf_uart_rxd_get(uart0_addr);
		uart0_cb.rx_counter++;
		if (uart0_cb.rx_timeout == 0) {
			rx_rdy_evt(dev);
		} else if (uart0_cb.rx_timeout != SYS_FOREVER_US) {
			k_timer_start(&uart0_cb.rx_timeout_timer,
				      K_USEC(uart0_cb.rx_timeout),
				      K_NO_WAIT);
		}
	}

	if (uart0_cb.rx_buffer_length == uart0_cb.rx_counter) {
		if (uart0_cb.rx_timeout != SYS_FOREVER_US) {
			k_timer_stop(&uart0_cb.rx_timeout_timer);
		}
		rx_rdy_evt(dev);

		unsigned int key = irq_lock();

		if (uart0_cb.rx_secondary_buffer_length == 0) {
			uart0_cb.rx_enabled = 0;
		}
		irq_unlock(key);

		if (uart0_cb.rx_secondary_buffer_length) {
			buf_released_evt(dev);
			/* Switch to secondary buffer. */
			uart0_cb.rx_buffer_length =
				uart0_cb.rx_secondary_buffer_length;
			uart0_cb.rx_buffer = uart0_cb.rx_secondary_buffer;
			uart0_cb.rx_secondary_buffer_length = 0;
			uart0_cb.rx_counter = 0;
			uart0_cb.rx_offset = 0;

			event.type = UART_RX_BUF_REQUEST;
			user_callback(dev, &event);
		} else {
			uart_nrfx_rx_disable(dev);
		}
	}
}

static void tx_isr(const struct device *dev)
{
	uart0_cb.tx_counter++;
	if (uart0_cb.tx_counter < uart0_cb.tx_buffer_length &&
	    !uart0_cb.tx_abort) {
#if	HW_FLOW_CONTROL_AVAILABLE
		if (uart0_cb.tx_timeout != SYS_FOREVER_US) {
			k_timer_start(&uart0_cb.tx_timeout_timer,
				      K_USEC(uart0_cb.tx_timeout),
				      K_NO_WAIT);
		}
#endif
		nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_TXDRDY);

		uint8_t txd = uart0_cb.tx_buffer[uart0_cb.tx_counter];

		nrf_uart_txd_set(uart0_addr, txd);
	} else {
#if	HW_FLOW_CONTROL_AVAILABLE

		if (uart0_cb.tx_timeout != SYS_FOREVER_US) {
			k_timer_stop(&uart0_cb.tx_timeout_timer);
		}
#endif
		nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPTX);
		struct uart_event event = {
			.type = UART_TX_DONE,
			.data.tx.buf = uart0_cb.tx_buffer,
			.data.tx.len = uart0_cb.tx_counter
		};
		nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_TXDRDY);
		uart0_cb.tx_buffer_length = 0;
		uart0_cb.tx_counter = 0;
		uart0_cb.tx_buffer = NULL;

		nrf_uart_int_disable(uart0_addr, NRF_UART_INT_MASK_TXDRDY);
		user_callback(dev, &event);
	}
}

#define UART_ERROR_FROM_MASK(mask) \
	(mask & NRF_UART_ERROR_OVERRUN_MASK ? UART_ERROR_OVERRUN	\
	 : mask & NRF_UART_ERROR_PARITY_MASK ? UART_ERROR_PARITY	\
	 : mask & NRF_UART_ERROR_FRAMING_MASK ? UART_ERROR_FRAMING	\
	 : mask & NRF_UART_ERROR_BREAK_MASK ? UART_BREAK		\
	 : 0)

static void error_isr(const struct device *dev)
{
	if (uart0_cb.rx_timeout != SYS_FOREVER_US) {
		k_timer_stop(&uart0_cb.rx_timeout_timer);
	}
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_ERROR);

	if (!uart0_cb.rx_enabled) {
		nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPRX);
	}
	struct uart_event event = {
		.type = UART_RX_STOPPED,											// ERROR CODE OCCURED 2023 05 25
		.data.rx_stop.reason =
			UART_ERROR_FROM_MASK(
				nrf_uart_errorsrc_get_and_clear(uart0_addr)),
		.data.rx_stop.data.len = uart0_cb.rx_counter
					 - uart0_cb.rx_offset,
		.data.rx_stop.data.offset = uart0_cb.rx_offset,
		.data.rx_stop.data.buf = uart0_cb.rx_buffer
	};

	user_callback(dev, &event);
	/* Abort transfer. */
	// uart_nrfx_rx_disable(dev);
}

/*
 * In nRF hardware RX timeout can occur only after stopping the peripheral,
 * it is used as a sign that peripheral has finished its operation and is
 * disabled.
 */
static void rxto_isr(const struct device *dev)
{
	nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXTO);

	/* Send rxrdy if there is any data pending. */
	if (uart0_cb.rx_counter - uart0_cb.rx_offset) {
		rx_rdy_evt(dev);
	}

	buf_released_evt(dev);
	if (uart0_cb.rx_secondary_buffer_length) {
		uart0_cb.rx_buffer = uart0_cb.rx_secondary_buffer;
		buf_released_evt(dev);
	}

	rx_reset_state();
	rx_disabled_evt(dev);
}

void uart_nrfx_isr(const struct device *uart)
{
	if (nrf_uart_int_enable_check(uart0_addr, NRF_UART_INT_MASK_ERROR) &&
	    nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_ERROR)) {
		error_isr(uart);
	} else if (nrf_uart_int_enable_check(uart0_addr,
					     NRF_UART_INT_MASK_RXDRDY) &&
		   nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXDRDY)) {
		rx_isr(uart);
	}

	if (nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_TXDRDY)
	    && nrf_uart_int_enable_check(uart0_addr,
					 NRF_UART_INT_MASK_TXDRDY)) {
		tx_isr(uart);
	}

	if (nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXTO)) {
		rxto_isr(uart);
	}
}

static void rx_timeout(struct k_timer *timer)
{
	rx_rdy_evt(DEVICE_DT_INST_GET(0));
}

#if HW_FLOW_CONTROL_AVAILABLE
static void tx_timeout(struct k_timer *timer)
{
	struct uart_event evt;

	if (uart0_cb.tx_timeout != SYS_FOREVER_US) {
		k_timer_stop(&uart0_cb.tx_timeout_timer);
	}
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPTX);
	evt.type = UART_TX_ABORTED;
	evt.data.tx.buf = uart0_cb.tx_buffer;
	evt.data.tx.len = uart0_cb.tx_buffer_length;
	uart0_cb.tx_buffer_length = 0;
	uart0_cb.tx_counter = 0;
	user_callback(DEVICE_DT_INST_GET(0), &evt);
}
#endif

#endif /* CONFIG_UART_0_ASYNC */


#ifdef CONFIG_UART_0_INTERRUPT_DRIVEN

/** Interrupt driven FIFO fill function */
static int uart_nrfx_fifo_fill(const struct device *dev,
			       const uint8_t *tx_data,
			       int len)
{
	uint8_t num_tx = 0U;

	while ((len - num_tx > 0) &&
	       event_txdrdy_check()) {

		/* Clear the interrupt */
		event_txdrdy_clear();

		/* Send a character */
		nrf_uart_txd_set(uart0_addr, (uint8_t)tx_data[num_tx++]);
	}

	return (int)num_tx;
}

/** Interrupt driven FIFO read function */
static int uart_nrfx_fifo_read(const struct device *dev,
			       uint8_t *rx_data,
			       const int size)
{
	uint8_t num_rx = 0U;

	while ((size - num_rx > 0) &&
	       nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXDRDY)) {
		/* Clear the interrupt */
		nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXDRDY);

		/* Receive a character */
		rx_data[num_rx++] = (uint8_t)nrf_uart_rxd_get(uart0_addr);
	}

	return num_rx;
}

/** Interrupt driven transfer enabling function */
static void uart_nrfx_irq_tx_enable(const struct device *dev)
{
	uint32_t key;

	disable_tx_irq = false;

	/* Indicate that this device started a transaction that should not be
	 * interrupted by putting the SoC into the deep sleep mode.
	 */
	pm_device_busy_set(dev);

	/* Activate the transmitter. */
	nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STARTTX);

	nrf_uart_int_enable(uart0_addr, NRF_UART_INT_MASK_TXDRDY);

	/* Critical section is used to avoid any UART related interrupt which
	 * can occur after the if statement and before call of the function
	 * forcing an interrupt.
	 */
	key = irq_lock();
	if (uart_sw_event_txdrdy) {
		/* Due to HW limitation first TXDRDY interrupt shall be
		 * triggered by the software.
		 */
		NVIC_SetPendingIRQ(IRQN);
	}
	irq_unlock(key);
}

/** Interrupt driven transfer disabling function */
static void uart_nrfx_irq_tx_disable(const struct device *dev)
{
	/* Disable TX interrupt in uart_nrfx_isr() when transmission is done. */
	disable_tx_irq = true;
}

/** Interrupt driven receiver enabling function */
static void uart_nrfx_irq_rx_enable(const struct device *dev)
{
	nrf_uart_int_enable(uart0_addr, NRF_UART_INT_MASK_RXDRDY);
}

/** Interrupt driven receiver disabling function */
static void uart_nrfx_irq_rx_disable(const struct device *dev)
{
	nrf_uart_int_disable(uart0_addr, NRF_UART_INT_MASK_RXDRDY);
}

/** Interrupt driven transfer empty function */
static int uart_nrfx_irq_tx_ready_complete(const struct device *dev)
{
	/* Signal TX readiness only when the TX interrupt is enabled and there
	 * is no pending request to disable it. Note that this function may get
	 * called after the TX interrupt is requested to be disabled but before
	 * the disabling is actually performed (in the IRQ handler).
	 */
	return nrf_uart_int_enable_check(uart0_addr,
					 NRF_UART_INT_MASK_TXDRDY) &&
	       !disable_tx_irq &&
	       event_txdrdy_check();
}

/** Interrupt driven receiver ready function */
static int uart_nrfx_irq_rx_ready(const struct device *dev)
{
	return nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_RXDRDY);
}

/** Interrupt driven error enabling function */
static void uart_nrfx_irq_err_enable(const struct device *dev)
{
	nrf_uart_int_enable(uart0_addr, NRF_UART_INT_MASK_ERROR);
}

/** Interrupt driven error disabling function */
static void uart_nrfx_irq_err_disable(const struct device *dev)
{
	nrf_uart_int_disable(uart0_addr, NRF_UART_INT_MASK_ERROR);
}

/** Interrupt driven pending status function */
static int uart_nrfx_irq_is_pending(const struct device *dev)
{
	return ((nrf_uart_int_enable_check(uart0_addr,
					   NRF_UART_INT_MASK_TXDRDY) &&
		 uart_nrfx_irq_tx_ready_complete(dev))
		||
		(nrf_uart_int_enable_check(uart0_addr,
					   NRF_UART_INT_MASK_RXDRDY) &&
		 uart_nrfx_irq_rx_ready(dev)));
}

/** Interrupt driven interrupt update function */
static int uart_nrfx_irq_update(const struct device *dev)
{
	return 1;
}

/** Set the callback function */
static void uart_nrfx_irq_callback_set(const struct device *dev,
				       uart_irq_callback_user_data_t cb,
				       void *cb_data)
{
	(void)dev;
	irq_callback = cb;
	irq_cb_data = cb_data;
}

/**
 * @brief Interrupt service routine.
 *
 * This simply calls the callback function, if one exists.
 *
 * @param arg Argument to ISR.
 */
static void uart_nrfx_isr(const struct device *dev)
{
	if (disable_tx_irq &&
	    nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_TXDRDY)) {
		nrf_uart_int_disable(uart0_addr, NRF_UART_INT_MASK_TXDRDY);

		/* Deactivate the transmitter so that it does not needlessly
		 * consume power.
		 */
		nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STOPTX);

		/* The transaction is over. It is okay to enter the deep sleep
		 * mode if needed.
		 */
		pm_device_busy_clear(dev);

		disable_tx_irq = false;

		return;
	}

	if (nrf_uart_event_check(uart0_addr, NRF_UART_EVENT_ERROR)) {
		nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_ERROR);
	}

	if (irq_callback) {
		irq_callback(dev, irq_cb_data);
	}
}
#endif /* CONFIG_UART_0_INTERRUPT_DRIVEN */

/**
 * @brief Initialize UART channel
 *
 * This routine is called to reset the chip in a quiescent state.
 * It is assumed that this function is called only once per UART.
 *
 * @param dev UART device struct
 *
 * @return 0 on success
 */
static int uart_nrfx_init(const struct device *dev)
{
	struct uart_nrfx_data *data = dev->data;
	int err;
#ifdef CONFIG_PINCTRL
	const struct uart_nrfx_config *config = dev->config;
#endif /* CONFIG_PINCTRL */

	nrf_uart_disable(uart0_addr);

#ifdef CONFIG_PINCTRL
	err = pinctrl_apply_state(config->pcfg, PINCTRL_STATE_DEFAULT);
	if (err < 0) {
		return err;
	}
#else
	uart_nrfx_pins_configure(dev, false);
#endif /* CONFIG_PINCTRL */

	/* Set initial configuration */
	err = uart_nrfx_configure(dev, &data->uart_config);
	if (err) {
		return err;
	}

	/* Enable the UART and activate its receiver. With the current API
	 * the receiver needs to be active all the time. The transmitter
	 * will be activated when there is something to send.
	 */
	nrf_uart_enable(uart0_addr);

	if (!DISABLE_RX) {
		nrf_uart_event_clear(uart0_addr, NRF_UART_EVENT_RXDRDY);

		nrf_uart_task_trigger(uart0_addr, NRF_UART_TASK_STARTRX);
	}

#ifdef CONFIG_UART_0_INTERRUPT_DRIVEN
	/* Simulate that the TXDRDY event is set, so that the transmitter status
	 * is indicated correctly.
	 */
	uart_sw_event_txdrdy = 1U;
#endif

#if defined(CONFIG_UART_0_ASYNC) || defined(CONFIG_UART_0_INTERRUPT_DRIVEN)

	IRQ_CONNECT(IRQN,
		    IRQ_PRIO,
		    uart_nrfx_isr,
		    DEVICE_DT_INST_GET(0),
		    0);
	irq_enable(IRQN);
#endif

#ifdef CONFIG_UART_0_ASYNC
	k_timer_init(&uart0_cb.rx_timeout_timer, rx_timeout, NULL);
#if HW_FLOW_CONTROL_AVAILABLE
	k_timer_init(&uart0_cb.tx_timeout_timer, tx_timeout, NULL);
#endif
#endif
	return 0;
}

/* Common function: uart_nrfx_irq_tx_ready_complete is used for two API entries
 * because Nordic hardware does not distinguish between them.
 */
static const struct uart_driver_api uart_nrfx_uart_driver_api = {
#ifdef CONFIG_UART_0_ASYNC
	.callback_set	  = uart_nrfx_callback_set,
	.tx		  = uart_nrfx_tx,
	.tx_abort	  = uart_nrfx_tx_abort,
	.rx_enable	  = uart_nrfx_rx_enable,
	.rx_buf_rsp	  = uart_nrfx_rx_buf_rsp,
	.rx_disable	  = uart_nrfx_rx_disable,
#endif /* CONFIG_UART_0_ASYNC */
	.poll_in          = uart_nrfx_poll_in,
	.poll_out         = uart_nrfx_poll_out,
	.err_check        = uart_nrfx_err_check,
#ifdef CONFIG_UART_USE_RUNTIME_CONFIGURE
	.configure        = uart_nrfx_configure,
	.config_get       = uart_nrfx_config_get,
#endif
#ifdef CONFIG_UART_0_INTERRUPT_DRIVEN
	.fifo_fill        = uart_nrfx_fifo_fill,
	.fifo_read        = uart_nrfx_fifo_read,
	.irq_tx_enable    = uart_nrfx_irq_tx_enable,
	.irq_tx_disable   = uart_nrfx_irq_tx_disable,
	.irq_tx_ready     = uart_nrfx_irq_tx_ready_complete,
	.irq_rx_enable    = uart_nrfx_irq_rx_enable,
	.irq_rx_disable   = uart_nrfx_irq_rx_disable,
	.irq_tx_complete  = uart_nrfx_irq_tx_ready_complete,
	.irq_rx_ready     = uart_nrfx_irq_rx_ready,
	.irq_err_enable   = uart_nrfx_irq_err_enable,
	.irq_err_disable  = uart_nrfx_irq_err_disable,
	.irq_is_pending   = uart_nrfx_irq_is_pending,
	.irq_update       = uart_nrfx_irq_update,
	.irq_callback_set = uart_nrfx_irq_callback_set,
#endif /* CONFIG_UART_0_INTERRUPT_DRIVEN */
};

#ifdef CONFIG_PM_DEVICE
static int uart_nrfx_pm_action(const struct device *dev,
			       enum pm_device_action action)
{
#ifdef CONFIG_PINCTRL
	const struct uart_nrfx_config *config = dev->config;
	int ret;
#endif

	switch (action) {
	case PM_DEVICE_ACTION_RESUME:
		if (IS_ENABLED(CONFIG_UART_0_GPIO_MANAGEMENT)) {
#ifdef CONFIG_PINCTRL
			ret = pinctrl_apply_state(config->pcfg,
						  PINCTRL_STATE_DEFAULT);
			if (ret < 0) {
				return ret;
			}
#else
			uart_nrfx_pins_configure(dev, false);
#endif /* CONFIG_PINCTRL */
		}

		nrf_uart_enable(uart0_addr);
		if (!DISABLE_RX) {
			nrf_uart_task_trigger(uart0_addr,
					      NRF_UART_TASK_STARTRX);
		}
		break;
	case PM_DEVICE_ACTION_SUSPEND:
		nrf_uart_disable(uart0_addr);

		if (IS_ENABLED(CONFIG_UART_0_GPIO_MANAGEMENT)) {
#ifdef CONFIG_PINCTRL
			ret = pinctrl_apply_state(config->pcfg,
						  PINCTRL_STATE_SLEEP);
			if (ret < 0) {
				return ret;
			}
#else
			uart_nrfx_pins_configure(dev, true);
#endif /* CONFIG_PINCTRL */
		}
		break;
	default:
		return -ENOTSUP;
	}

	return 0;
}
#endif /* CONFIG_PM_DEVICE */

#ifdef CONFIG_PINCTRL
PINCTRL_DT_INST_DEFINE(0);
#endif /* CONFIG_PINCTRL */

NRF_DT_CHECK_PIN_ASSIGNMENTS(DT_DRV_INST(0), 1,
			     tx_pin, rx_pin, rts_pin, cts_pin);

static const struct uart_nrfx_config uart_nrfx_uart0_config = {
#ifdef CONFIG_PINCTRL
	.pcfg = PINCTRL_DT_INST_DEV_CONFIG_GET(0),
#else
	.tx_pin = DT_INST_PROP_OR(0, tx_pin, NRF_UART_PSEL_DISCONNECTED),
	.rx_pin = DT_INST_PROP_OR(0, rx_pin, NRF_UART_PSEL_DISCONNECTED),
	.rts_pin = DT_INST_PROP_OR(0, rts_pin, NRF_UART_PSEL_DISCONNECTED),
	.cts_pin = DT_INST_PROP_OR(0, cts_pin, NRF_UART_PSEL_DISCONNECTED),
	.rx_pull_up = DT_INST_PROP(0, rx_pull_up),
	.cts_pull_up = DT_INST_PROP(0, cts_pull_up)
#endif /* CONFIG_PINCTRL */
};

static struct uart_nrfx_data uart_nrfx_uart0_data = {
	.uart_config = {
		.stop_bits = UART_CFG_STOP_BITS_1,
		.data_bits = UART_CFG_DATA_BITS_8,
		.baudrate  = BAUDRATE,
#ifdef CONFIG_UART_0_NRF_PARITY_BIT
		.parity    = UART_CFG_PARITY_EVEN,
#else
		.parity    = UART_CFG_PARITY_NONE,
#endif /* CONFIG_UART_0_NRF_PARITY_BIT */
		.flow_ctrl = PROP(hw_flow_control) ?
			UART_CFG_FLOW_CTRL_RTS_CTS : UART_CFG_FLOW_CTRL_NONE,
	}
};

PM_DEVICE_DT_INST_DEFINE(0, uart_nrfx_pm_action);

DEVICE_DT_INST_DEFINE(0,
	      uart_nrfx_init,
	      PM_DEVICE_DT_INST_GET(0),
	      &uart_nrfx_uart0_data,
	      &uart_nrfx_uart0_config,
	      /* Initialize UART device before UART console. */
	      PRE_KERNEL_1,
	      CONFIG_SERIAL_INIT_PRIORITY,
	      &uart_nrfx_uart_driver_api);

static void uartCallback(const struct device *dev, struct uart_event *evt, void *user_data)
{
    int err;
    static uint16_t pos;

    ARG_UNUSED(user_data);

    switch (evt->type) {
        case UART_TX_DONE:
            sendData(0x01);
            break;
        case UART_TX_ABORTED:
            sendData(0x02);
            break;
        case UART_RX_RDY:
            for (int i = pos; i < (pos + evt->data.rx.len); i++) 
            {
                if( ++UART_BUF->head == MAX_UART_BUF_SIZE )
                {
                    UART_BUF->head = 0;
                }
                sendData(evt->data.rx.buf[i]);
                UART_BUF->queue[UART_BUF->head] = evt->data.rx.buf[i];                   // data save
                if( UART_BUF->head == UART_BUF->tail )
                {
                    UART_BUF->overflow = 1;
                }
            }
            pos += evt->data.rx.len;
            break;
        case UART_RX_BUF_REQUEST:
            pos = 0;
            err = uart_rx_buf_rsp(pUartDev, pNextUartBuf, sizeof(uartRxBuf[0]));
            if (err) {
                LOG_ERR("UART RX buf rsp: %d", err);
            }
            sendData(0x03);
            break;
        case UART_RX_BUF_RELEASED:
            sendData(0x04);
            pNextUartBuf = evt->data.rx_buf.buf;
            break;
        case UART_RX_STOPPED:
            sendData(0x05);
            uartErr = evt->data.rx_stop.reason;
            break;
        case UART_RX_DISABLED:
            sendData(0x06);
            break;
        default:
            break;
    }
}

When sending 21 bytes, the output is functioning correctly for about 12 to 13 bytes. However, after that, when it transitions to the UART_RX_STOPPED state, the output becomes 0x05.

I would be grateful if you could provide me with the details of the problem you're facing so that I can assist you in finding a solution.

Additionally, there was no applicable error source for the explanation provided earlier.

Here is a captured picture of entering the error ISR (Interrupt Service Routine) in debug mode.

[Håkon Alseth]

Hi,

 

You are currently selecting NRF_UART, and not the DMA capable NRF_UARTE peripheral.

Could you try with the NRF_UARTE peripheral instead? This is done by selecting nrf-uarte in device tree:

compatible = "nordic,nrf-uarte";

 

Kind regards,

Håkon

[dcjin]

I don't know how to modify it to use UARTE.

Do I need to use a different driver?

[dcjin]

I was using nRF Connect SDK v1.5.0 in the Toolchain Manager of nRF Connect for Desktop, but I changed it to nRF Connect SDK v2.1.0.

I didn't encounter this issue with nRF Connect SDK v1.5.0, even though the source code remains the same.

Why is this happening?

I tried using UARTE in Kconfig, but it failed to build due to an error.

[Håkon Alseth]

Hi,

 

In order to use the UARTE peripheral, you set this in your overlay file.

That should be in my_project/boards/my_board.overlay

 

If you are using nRF52833 DK board, replace "my_board.overlay" with "nrf52833dk_nrf52833.overlay".

 

And contain something like this:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.3.99-ncs1/boards/arm/nrf52dk_nrf52832/nrf52dk_nrf52832.dts#L146

 

Ie.

&uart0 
{
    compatible = "nordic,nrf-uarte";
};

 

Kind regards,

Håkon