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LucasM's avatar
LucasM
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7 years ago
Solved

How to read from stdin in NIOSII with the small_c_library

whithout the small_c_library checked, i am unable to read from standard input. unless there's some sort of alt_fopen, how do i read from the standard character streams whithout gets,scanf and fopen?...
  • LucasM's avatar
    LucasM
    7 years ago

    It seems that with the small c library enabled stdin,stdou and stderr are "preopened" files, so i can interact with them as files whithout opening them, can't find right now exactly where i saw this info.

LucasM's avatar
LucasM
Icon for New Contributor rankNew Contributor
7 years ago

Yes, i am able to read incoming data (from the uart) with the full C library, using:

#include <stdio.h>
#include <stdlib.h>
 
FILE * fp;
 
char msg[255];
fp = fopen("/dev/uart_0","r");
		if(fp)
		{
			fscanf(fp,"%s",msg);
                  }

I've tried using the alt library, but it fails with:

home/user/project_name/software/nios_project_name_bsp/HAL/src/alt_getchar.c:67: undefined reference to `getc'
//source snippet
int 
alt_getchar(void)
{
#ifdef ALT_SEMIHOSTING
    char c;
    read(STDIN_FILENO,&c,1);
    return c;
#else
#ifdef ALT_USE_DIRECT_DRIVERS
    ALT_DRIVER_READ_EXTERNS(ALT_STDIN_DEV);
    char c;
 
    if (ALT_DRIVER_READ(ALT_STDIN_DEV, &c, 1, alt_fd_list[STDIN_FILENO].fd_flags) <= 0) {
        return -1;
    }
    return c;
#else
    return getchar();
#endif
#endif
}

It seems that the direct device drivers aren't available, and neither is getc.

is it some header missing or something similar?