gpioIrq.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>

 /****************************************************************
 * Constants
 ****************************************************************/

#define SYSFS_GPIO_DIR "/sys/class/gpio"
#define POLL_TIMEOUT (3 * 1000) /* 3 seconds */
#define MAX_BUF 64

/****************************************************************
 * gpio_export
 ****************************************************************/
int gpio_export(unsigned int gpio)
{
	int fd, len;
	char buf[MAX_BUF];

	fd = open(SYSFS_GPIO_DIR "/export", O_WRONLY);
	if (fd < 0) {
		perror("gpio/export");
		return fd;
	}

	len = snprintf(buf, sizeof(buf), "%d", gpio);
	write(fd, buf, len);
	close(fd);

	return 0;
}

/****************************************************************
 * gpio_unexport
 ****************************************************************/
int gpio_unexport(unsigned int gpio)
{
	int fd, len;
	char buf[MAX_BUF];

	fd = open(SYSFS_GPIO_DIR "/unexport", O_WRONLY);
	if (fd < 0) {
		perror("gpio/export");
		return fd;
	}

	len = snprintf(buf, sizeof(buf), "%d", gpio);
	write(fd, buf, len);
	close(fd);
	return 0;
}

/****************************************************************
 * gpio_set_dir
 ****************************************************************/
int gpio_set_dir(unsigned int gpio, unsigned int out_flag)
{
	int fd, len;
	char buf[MAX_BUF];

	len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR  "/gpio%d/direction", gpio);

	fd = open(buf, O_WRONLY);
	if (fd < 0) {
		perror("gpio/direction");
		return fd;
	}

	if (out_flag)
		write(fd, "out", 4);
	else
		write(fd, "in", 3);

	close(fd);
	return 0;
}

/****************************************************************
 * gpio_set_value
 ****************************************************************/
int gpio_set_value(unsigned int gpio, unsigned int value)
{
	int fd, len;
	char buf[MAX_BUF];

	len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);

	fd = open(buf, O_WRONLY);
	if (fd < 0) {
		perror("gpio/set-value");
		return fd;
	}

	if (value)
		write(fd, "1", 2);
	else
		write(fd, "0", 2);

	close(fd);
	return 0;
}

/****************************************************************
 * gpio_get_value
 ****************************************************************/
int gpio_get_value(unsigned int gpio, unsigned int *value)
{
	int fd, len;
	char buf[MAX_BUF];
	char ch;

	len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);

	fd = open(buf, O_RDONLY);
	if (fd < 0) {
		perror("gpio/get-value");
		return fd;
	}

	read(fd, &ch, 1);

	if (ch != '0') {
		*value = 1;
	} else {
		*value = 0;
	}

	close(fd);
	return 0;
}


/****************************************************************
 * gpio_set_edge
 ****************************************************************/

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) {
		perror("gpio/set-edge");
		return fd;
	}

	write(fd, edge, strlen(edge) + 1);
	close(fd);
	return 0;
}

/****************************************************************
 * gpio_fd_open
 ****************************************************************/

int gpio_fd_open(unsigned int gpio)
{
	int fd, len;
	char buf[MAX_BUF];

	len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);

	fd = open(buf, O_RDONLY | O_NONBLOCK );
	if (fd < 0) {
		perror("gpio/fd_open");
	}
	return fd;
}

/****************************************************************
 * gpio_fd_close
 ****************************************************************/

int gpio_fd_close(int fd)
{
	return close(fd);
}

/****************************************************************
 * Main
 ****************************************************************/
int main(int argc, char **argv, char **envp)
{
	struct pollfd fdset[2];
	int nfds = 2;
	int gpio_fd, timeout, rc;
	char *buf[MAX_BUF];
	unsigned int gpio;
	int len;
	int val;



	if (argc < 2) {
		printf("Usage: gpioIrq <gpio-pin>\n\n");
		printf("Waits for a change in the GPIO pin voltage level or input on stdin\n");
		exit(-1);
	}

	gpio = atoi(argv[1]);

	gpio_export(gpio);
	gpio_set_dir(gpio, 0);
	gpio_set_edge(gpio, "both");
	gpio_fd = gpio_fd_open(gpio);

	timeout = POLL_TIMEOUT;

	while (1) {
		memset((void*)fdset, 0, sizeof(fdset));

		fdset[0].fd = STDIN_FILENO;
		fdset[0].events = POLLIN;

		fdset[1].fd = gpio_fd;
		fdset[1].events = POLLPRI;

		rc = poll(fdset, nfds, timeout);

		if (rc < 0) {
			printf("\npoll() failed!\n");
			return -1;
		}

		if (rc == 0) {
			printf(".");
		}

		if (fdset[1].revents & POLLPRI) {
			lseek(fdset[1].fd, 0, SEEK_SET);
			len = read(fdset[1].fd, buf, MAX_BUF);
			printf("\npoll() GPIO %d interrupt occurred\n", gpio);
			printf("\tread value: '%c'\n", buf[0]);
		}

		if (fdset[0].revents & POLLIN) {
			(void)read(fdset[0].fd, buf, 1);
			printf("\npoll() stdin read 0x%2.2X\n", (unsigned int) buf[0]);
		}

		fflush(stdout);
	}

	gpio_fd_close(gpio_fd);
	return 0;
}