GPIO on Beaglebone Black

Question

I'm currently stuck on a problem with GPIO pins with the Beaglebone black.

I am looking for a proper way to read the values from GPIO pin p8_4 in C. I tried to use a library which used an old not supported way from the time before device tree's where introduced, if I understand this correctly.

I tried to find other solutions to my problem but I can't seem to find one. Is there anyone who can get me on the right track in C?

Answer 1

Here is a C code:

#include <stdio.h>


int main()
{
    FILE *io,*iodir,*ioval;

    io = fopen("/sys/class/gpio/export", "w");
    fseek(io,0,SEEK_SET);
    fprintf(io,"%d",39);
    fflush(io);

    iodir = fopen("/sys/class/gpio/gpio39/direction", "w");
    fseek(iodir,0,SEEK_SET);
    fprintf(iodir,"out");
    fflush(iodir);

    ioval = fopen("/sys/class/gpio/gpio39/value", "w");
    fseek(ioval,0,SEEK_SET);

    while(1)
    {
        fprintf(ioval,"%d",1);
        fflush(ioval);
        sleep(1);
        fprintf(ioval,"%d",0);
        fflush(ioval);
        sleep(1);
    }

    fclose(io);
    fclose(iodir);
    fclose(ioval);
    return 0;
}

Be sure to do proper error checking.

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