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STM32F7 GCC printf

Question asked by PeterLup2 on Jul 17, 2015
Latest reply on Feb 5, 2016 by Amel N
Hello.
I'm trying, for the first time in my life, to implement the printf/scanf functions on GCC.

I managed to get the UART working in interrupt mode but somehow I can not do the easiest part. That is, I can not retarget the printf.

I read that I needed to change the _write and _read function on syscalls.c so I did it. As a result, I can print only one character and then, the printf goes to HARD_FAULT.

I also tried to use the retarget.c file that I used on keil and it compiled exept from the ferror fuction. But it did nothing.

Below, I show my syscalls.c file.

I'm using System Worbench for stm32 with gcc.

thanks

/* 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>
#include "serialport.h"
 
 
/* Variables */
//#undef errno
extern int errno;
extern int __io_putchar(int ch) __attribute__((weak));
extern int __io_getchar(void) __attribute__((weak));
 
register char * stack_ptr asm("sp");
 
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 */
}
 
int _read (int file, char *ptr, int len)
{
    int DataIdx;
 
    for (DataIdx = 0; DataIdx < len; DataIdx++)
    {
        //*ptr++ = __io_getchar();
        *ptr++ = GetKey();
    }
 
return len;
}
 
int _write(int file, char *ptr, int len)
{
    int DataIdx;
 
    for (DataIdx = 0; DataIdx < len; DataIdx++)
    {
        //__io_putchar(*ptr++);
        SendChar((*ptr++));
    }
    return len;
}
 
caddr_t _sbrk(int incr)
{
    extern char end asm("end");
    static char *heap_end;
    char *prev_heap_end;
 
    if (heap_end == 0)
        heap_end = &end;
 
    prev_heap_end = heap_end;
    if (heap_end + incr > stack_ptr)
    {
//      write(1, "Heap and stack collision\n", 25);
//      abort();
        errno = ENOMEM;
        return (caddr_t) -1;
    }
 
    heap_end += incr;
 
    return (caddr_t) prev_heap_end;
}
 
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;
}

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