odroid-c4:application_note:gpio:irq

Hardware GPIO-IRQ

ODROID-N2 and ODROID-C4 support the GPIO interrupt with edge triggers.

Usage

Download the source code and build with gcc.

target
gcc -o gpio_irq_test gpio_irq_test.c

Basic usage is in the below. You have to put the two arguments for GPIO number and Edge type. And you can set Pull mode optionally by third parameter.

target
root@odroid:~$ ./gpio_sysfs_irq_test
usage : sudo sysfs_irq_test <gpio> <edge> [pull]

Source Code

gpio_irq_test.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <poll.h>
 
#define	SYSFS_GPIO_DIR	"/sys/class/gpio"
#define	MAX_BUF		255
 
int gpio_export(unsigned int gpio)
{
	int fd, len;
	char buf[MAX_BUF];
 
	fd = open(SYSFS_GPIO_DIR "/export", O_WRONLY);
 
	if (fd < 0) {
		fprintf(stderr, "Can't export GPIO %d pin: %s\n", gpio, strerror(errno));
		return fd;
	}
 
	len = snprintf(buf, sizeof(buf), "%d", gpio);
	write(fd, buf, len);
	close(fd);
 
	return 0;
}
 
int gpio_unexport(unsigned int gpio)
{
	int fd, len;
	char buf[MAX_BUF];
 
	fd = open(SYSFS_GPIO_DIR "/unexport", O_WRONLY);
 
	if (fd < 0) {
		fprintf(stderr, "Can't unexport GPIO %d pin: %s\n", gpio, strerror(errno));
		return fd;
	}
 
	len = snprintf(buf, sizeof(buf), "%d", gpio);
	write(fd, buf, len);
	close(fd);
 
	return 0;
}
 
int gpio_set_edge(unsigned int gpio, char *edge)
{
	int fd, len;
	char buf[MAX_BUF];
 
	len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/edge", gpio);
 
	fd = open(buf, O_WRONLY);
 
	if (fd < 0) {
		fprintf(stderr, "Can't set GPIO %d pin edge: %s\n", gpio, strerror(errno));
		return fd;
	}
 
	write(fd, edge, strlen(edge)+1);
	close(fd);
 
	return 0;
}
 
int gpio_set_pull(unsigned int gpio, char *pull)
{
	int fd, len;
	char buf[MAX_BUF];
 
	len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/pull", gpio);
 
	fd = open(buf, O_WRONLY);
 
	if (fd < 0) {
		fprintf(stderr, "Can't set GPIO %d pin pull: %s\n", gpio, strerror(errno));
		return fd;
	}
 
	write(fd, pull, strlen(pull)+1);
	close(fd);
 
	return 0;
}
 
int main(int argc, char *argv[])
{
	struct pollfd fdset[2];
	int fd, ret, gpio;
	char buf[MAX_BUF];
 
	if (argc < 3 || argc > 4)	{
		fprintf(stdout, "usage : sudo sysfs_irq_test <gpio> <edge> [pull]\n");
		fflush(stdout);
		return	-1;
	}
 
	gpio = atoi(argv[1]);
	if (gpio_export(gpio))	{
		fprintf(stdout, "error : export %d\n", gpio);
		fflush(stdout);
		return	-1;
	}
 
	if (gpio_set_edge(gpio, argv[2])) {
		fprintf(stdout, "error : edge %s\n", argv[2]);
		fflush(stdout);
		return	-1;
	}
 
	if (argv[3] && gpio_set_pull(gpio, argv[3])) { 
		fprintf(stdout, "error : pull %s\n", argv[3]);
		fflush(stdout);
		return	-1;
	}
 
	snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);
	fd = open(buf, O_RDWR);
	if (fd < 0)
		goto out;
 
	while (1) {
		memset(fdset, 0, sizeof(fdset));
		fdset[0].fd = STDIN_FILENO;
		fdset[0].events = POLLIN;
		fdset[1].fd = fd;
		fdset[1].events = POLLPRI;
		ret = poll(fdset, 2, 3*1000);
 
		if (ret < 0) {
			perror("poll");
			break;
		}
 
		fprintf(stderr, ".");
 
		if (fdset[1].revents & POLLPRI) {
			char c;
			(void)read (fd, &c, 1) ;
			lseek (fd, 0, SEEK_SET) ;
			fprintf(stderr, "\nGPIO %d interrupt occurred!\n", gpio);
		}
 
		if (fdset[0].revents & POLLIN)
			break;
 
		fflush(stdout);
	}
 
	close(fd);
out:
	if (gpio_unexport(gpio))	{
		fprintf(stdout, "error : unexport %d\n", gpio);
		fflush(stdout);
	}
 
	return 0;
 }

Here is an using example with the following parameters.

  • GPIO Number: 492
  • Edge: rising
  • Pull: up
target
odroid@odroid:~$ ./gpio_irq_test 492 rising up
.
GPIO 492 interrupt occurred!
...
GPIO 492 interrupt occurred!
.
GPIO 492 interrupt occurred!
.
GPIO 492 interrupt occurred!
.
GPIO 492 interrupt occurred!
2020/03/19 10:02 · luke.go
  • odroid-c4/application_note/gpio/irq.txt
  • Last modified: 2020/04/23 16:09
  • by luke.go