NUCLEO L496ZG SWO not able to make it work

[RPG]

Hi

I am trying to enable the SWO to debug with printf. I have a NUCLEO L496ZG board. The ITM_SendChar function seems to get called but no data on the ITM console. What am I doing wrong?

This is the main.c code:

/**
 ******************************************************************************
 * @file      syscalls.c
 * @author    Auto-generated by STM32CubeIDE
 * @brief     STM32CubeIDE Minimal System calls file
 *
 *            For more information about which c-functions
 *            need which of these lowlevel functions
 *            please consult the Newlib libc-manual
 ******************************************************************************
 * @attention
 *
 * Copyright (c) 2022 STMicroelectronics.
 * All rights reserved.
 *
 * This software is licensed under terms that can be found in the LICENSE file
 * in the root directory of this software component.
 * If no LICENSE file comes with this software, it is provided AS-IS.
 *
 ******************************************************************************
 */
 
/* Includes */
#include <sys/stat.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#include <time.h>
#include <sys/time.h>
#include <sys/times.h>
 
/////////////////////////////////////////////////////////////////////////////////////////////////////////
//					Implementation of printf like feature using ARM Cortex M3/M4/ ITM functionality
//					This function will not work for ARM Cortex M0/M0+
//					If you are using Cortex M0, then you can use semihosting feature of openOCD
/////////////////////////////////////////////////////////////////////////////////////////////////////////
 
 
//Debug Exception and Monitor Control Register base address
#define DEMCR        			*((volatile uint32_t*) 0xE000EDFCU )
 
/* ITM register addresses */
#define ITM_STIMULUS_PORT0   	*((volatile uint32_t*) 0xE0000000 )
#define ITM_TRACE_EN          	*((volatile uint32_t*) 0xE0000E00 )
 
void ITM_SendChar(uint8_t ch)
{
 
	//Enable TRCENA
	DEMCR |= ( 1 << 24);
 
	//enable stimulus port 0
	ITM_TRACE_EN |= ( 1 << 0);
 
	// read FIFO status in bit [0]:
	while(!(ITM_STIMULUS_PORT0 & 1));
 
	//Write to ITM stimulus port0
	ITM_STIMULUS_PORT0 = ch;
}
 
 
/* Variables */
extern int __io_putchar(int ch) __attribute__((weak));
extern int __io_getchar(void) __attribute__((weak));
 
 
char *__env[1] = { 0 };
char **environ = __env;
 
 
/* Functions */
void initialise_monitor_handles()
{
}
 
int _getpid(void)
{
	return 1;
}
 
int _kill(int pid, int sig)
{
	errno = EINVAL;
	return -1;
}
 
void _exit (int status)
{
	_kill(status, -1);
	while (1) {}		/* Make sure we hang here */
}
 
__attribute__((weak)) int _read(int file, char *ptr, int len)
{
	int DataIdx;
 
	for (DataIdx = 0; DataIdx < len; DataIdx++)
	{
		*ptr++ = __io_getchar();
	}
 
return len;
}
 
__attribute__((weak)) int _write(int file, char *ptr, int len)
{
	int DataIdx;
 
	for (DataIdx = 0; DataIdx < len; DataIdx++)
	{
		//__io_putchar(*ptr++);
		ITM_SendChar(*ptr++);
	}
	return len;
}
 
int _close(int file)
{
	return -1;
}
 
 
int _fstat(int file, struct stat *st)
{
	st->st_mode = S_IFCHR;
	return 0;
}
 
int _isatty(int file)
{
	return 1;
}
 
int _lseek(int file, int ptr, int dir)
{
	return 0;
}
 
int _open(char *path, int flags, ...)
{
	/* Pretend like we always fail */
	return -1;
}
 
int _wait(int *status)
{
	errno = ECHILD;
	return -1;
}
 
int _unlink(char *name)
{
	errno = ENOENT;
	return -1;
}
 
int _times(struct tms *buf)
{
	return -1;
}
 
int _stat(char *file, struct stat *st)
{
	st->st_mode = S_IFCHR;
	return 0;
}
 
int _link(char *old, char *new)
{
	errno = EMLINK;
	return -1;
}
 
int _fork(void)
{
	errno = EAGAIN;
	return -1;
}
 
int _execve(char *name, char **argv, char **env)
{
	errno = ENOMEM;
	return -1;
}

In syscalls.c file I have replaced the _write function:

__attribute__((weak)) int _write(int file, char *ptr, int len)
{
	int DataIdx;
 
	for (DataIdx = 0; DataIdx < len; DataIdx++)
	{
		//__io_putchar(*ptr++);
		ITM_SendChar(*ptr++);
	}
	return len;
}

This are the settings on the ioc project file:

 

And this are the settings on Debug configuration:

 

And the ITM settings:

This is my board:

 

PB3 is connected to SWO.

Thanks in advance.

[Tesla DeLorean · Accepted solution]

And you're clocking the MCU at 16 or 80 MHz?​

[RPG]

That was the issue. Thank you. Didn't set correctly the clock on IOC settings. Now is 16 MHz and it works.

 

Thank you very much!

[FBL]

Hi @Raúl Pérez Gómez​, 

For more information, please refer to AN4989 STM32 microcontroller debug toolbox section 7.3 describes the Printf via SWO/SWV. Also, this article How to use semihosting with STM32CubeIDE and STM32 may be useful.

Firas