View source for Manage the GPIO lines in C with libgpiod

== Manage the GPIO lines in C with libgpiod ==

Since linux 4.8 the GPIO sysfs interface is deprecated. User space should use the character device instead. 

'''libgpiod''' encapsulates the ioctl calls and data structures behind a straightforward API.


== Manage the GPIO using the C language ==


- [https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/tree/README libgpiod documentation]

- [https://github.com/starnight/libgpiod-example libgpiod-example git repo]



== Example ==


  #include <gpiod.h>
  #include <stdio.h>
  #include <unistd.h>
  
  #ifndef	CONSUMER
  #define	CONSUMER	"Consumer"
  #endif
  
  int main(int argc, char **argv)
  {
    char *chipname = "gpiochip0";
    unsigned int line_num = 23;	// GPIO Pin #23
    unsigned int val;
    struct gpiod_chip *chip;
    struct gpiod_line *line;
    int i, ret;
  
    chip = gpiod_chip_open_by_name(chipname);
    if (!chip) {
      perror("Open chip failed\n");
      goto end;
    }
  
    line = gpiod_chip_get_line(chip, line_num);
    if (!line) {
      perror("Get line failed\n");
      goto close_chip;
    }
  
    ret = gpiod_line_request_output(line, CONSUMER, 0);
    if (ret < 0) {
      perror("Request line as output failed\n");
      goto release_line;
    }
  
    /* Blink 20 times */
    val = 0;
    for (i = 20; i > 0; i--) {
      ret = gpiod_line_set_value(line, val);
      if (ret < 0) {
        perror("Set line output failed\n");
        goto release_line;
      }
      printf("Output %u on line #%u\n", val, line_num);
      sleep(1);
      val = !val;
    }
  
  release_line:
    gpiod_line_release(line);
  close_chip:
    gpiod_chip_close(chip);
  end:
    return 0;
  }