Hardware GPIO-IRQ

ODROID-C1 supports the GPIO interrupt of Edge trigger.
The maximum number of interrupt is limited to 8 when you use the falling(Low) or rising(High) edge trigger.
If you use the Both (rising and falling together) edge triggers, the maximum number is only 4.

You must use the Linux 3.10.79-87 June or higher to use the GPIO interrupt in the user-land.

To use the GPIO Interrupt in the User space, you must export the GPIO and add the Trigger option in Edge parameter.

GPIO SYSFS node is accessible via /sys/class/aml_gpio/. The access method is exactly same as /sys/class/gpio.

echo [GPIO Number(Refer expansion_connectors )] > /sys/class/aml_gpio/export

e.g) GPIOY.BIT3 Export (Pin Number 7)

echo 83 > /sys/class/aml_gpio/export

This C example code shows the status of GPIO interrupts in the User Space.
This example uses Both(rising + falling) edges on the GPIO Pin 7.

gcc -o aml_gpio_irq_test aml_gpio_irq_test.c

sudo aml_gpio_irq_test [GPIO Number]

aml_gpio_irq.c

//[*]-------------------------------------------------------------------------[*]
//
//  GPIO IRQ Test Application for AMLogic.
//
//[*]-------------------------------------------------------------------------[*]
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>
#include <sched.h>
 
//[*]-------------------------------------------------------------------------[*]
#define SYSFS_GPIO_DIR  "/sys/class/aml_gpio"
#define POLL_TIMEOUT    (3 * 1000) /* 3 seconds */
#define MAX_BUF         64
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
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;
}
 
//[*]-------------------------------------------------------------------------[*]
int gpio_fd_close(int fd)
{
	return close(fd);
}
 
//[*]-------------------------------------------------------------------------[*]
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;
 
	if (argc < 2) {
		printf("Usage: aml_gpio_irq <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");    // High/Low Edge Trigger
	gpio_fd = gpio_fd_open(gpio);
 
	timeout = POLL_TIMEOUT;
 
    // set a high priority schedulling for the running program
    {
        struct sched_param sched ;
 
        memset (&sched, 0, sizeof(sched)) ;
 
        sched.sched_priority = 55;
 
        sched_setscheduler (0, SCHED_RR, &sched) ;
    }
 
	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("POLL Timeout!\n");
		}
 
		if (fdset[1].revents & POLLPRI) {
			len = read(fdset[1].fd, buf, MAX_BUF);
			printf("\npoll() GPIO %d interrupt occurred\n", gpio);
		}
 
		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;
}
 
//[*]-------------------------------------------------------------------------[*]
//[*]-------------------------------------------------------------------------[*]