nRF52DK nRF52832 UART asynchronous receive

[zazas321]

I am working through the Nordic Developer Academy and got stuck at lesson 4 (UART receive)

https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/lessons/lesson-4-serial-communication-uart/topic/uart-driver/

In particular, I am confused about this part:

I have created a sample project and connected external CP2102 USB->Serial adapter to P0.06 and P0.08 pins.

The code that I use:

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/*

* Copyright (c) 2012-2014 Wind River Systems, Inc.

*

* SPDX-License-Identifier: Apache-2.0

*/

#include <zephyr/kernel.h>

#include <zephyr/drivers/gpio.h>

#include "stdio.h"

#include "zephyr/drivers/uart.h"

const struct device *uart = DEVICE_DT_GET(DT_NODELABEL(uart0));

static uint8_t tx_buf[] = {"nRF Connect SDK Fundamentals Course \n\r"};

static uint8_t rx_buf[10] = {0}; //A buffer to store incoming UART data

const struct uart_config uart_cfg = {

.baudrate = 115200,

.parity = UART_CFG_PARITY_NONE,

.stop_bits = UART_CFG_STOP_BITS_1,

.data_bits = UART_CFG_DATA_BITS_8,

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

#include <zephyr/kernel.h>
#include <zephyr/drivers/gpio.h>
#include "stdio.h"
#include "zephyr/drivers/uart.h"

const struct device *uart = DEVICE_DT_GET(DT_NODELABEL(uart0));

static uint8_t tx_buf[] =  {"nRF Connect SDK Fundamentals Course \n\r"};
static uint8_t rx_buf[10] = {0}; //A buffer to store incoming UART data 

const struct uart_config uart_cfg = {
		.baudrate = 115200,
		.parity = UART_CFG_PARITY_NONE,
		.stop_bits = UART_CFG_STOP_BITS_1,
		.data_bits = UART_CFG_DATA_BITS_8,
		.flow_ctrl = UART_CFG_FLOW_CTRL_NONE
	};

static void uart_cb(const struct device *dev, struct uart_event *evt, void *user_data)
{
	switch (evt->type) {
	
	case UART_TX_DONE:
		printf("transmission complete \n");
		break;

	case UART_TX_ABORTED:
		// do something
		break;
		
	case UART_RX_RDY:
		printf("rx rdy \n");
		if((evt->data.rx.len) != 0){
			printf("data received = %s \n", evt->data.rx.buf[evt->data.rx.offset]);
		}


		
		break;

	case UART_RX_BUF_REQUEST:
		printf("requesting buffer \n");
		// do something
		break;

	case UART_RX_BUF_RELEASED:
		printf("buffer released \n");
		// do something
		break;
		
	case UART_RX_DISABLED:
		printf("rx disabled \n");
		uart_rx_enable(dev, rx_buf, sizeof(rx_buf), 100);
		break;

	case UART_RX_STOPPED:
		// do something
		break;
		
	default:
		break;
	}
}


int main(void)
{	

	if (!device_is_ready(uart)) {
    	return;
	}

	int err;
	err = uart_callback_set(uart, uart_cb, NULL);
	if (err) {
		return err;
	}

	uart_rx_enable(uart, rx_buf, sizeof(rx_buf), 100);


	err = uart_tx(uart, tx_buf, sizeof(tx_buf), SYS_FOREVER_US);
	if (err) {
		return err;
	}



	while(1){
		k_msleep(1000);
	}
	return 0;
}

I am having issues understanding how to properly print out all the received data:

I tried to do:

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case UART_RX_RDY:

printf("rx rdy \n");

if((evt->data.rx.len) != 0){

printf("data received = %s \n", evt->data.rx.buf[evt->data.rx.offset]);

}

break;

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	case UART_RX_RDY:
		printf("rx rdy \n");
		if((evt->data.rx.len) != 0){
			printf("data received = %s \n", evt->data.rx.buf[evt->data.rx.offset]);
		}

		break;

but when I send the data via UART (using Termite) , the following is printed:

I would appreciate if someone could clarify how to correctly print out all the received data.  Thanks in advance

Just for testing, I have also tried to print:

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case UART_RX_RDY:

printf("rx rdy \n");

printf("data: %s \n", rx_buf);

break;

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    case UART_RX_RDY:
        printf("rx rdy \n");
        printf("data: %s \n", rx_buf);
        break;

 

and the logs are as following: (captured using Termite):

 

As you can see, it receives the first message (ping) correctly, but after that, the buffer overflows (rx_buf is 10 bytes size) and then it cannot print out the data correctly)