122 lines
2.4 KiB
C
122 lines
2.4 KiB
C
/*
|
|
SYSFS gpio interrupt example for Raspberry Pi
|
|
*/
|
|
#define _GNU_SOURCE
|
|
#include <stddef.h>
|
|
#include <unistd.h>
|
|
#include <string.h>
|
|
#include <stdio.h>
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <fcntl.h>
|
|
#include <poll.h>
|
|
#include "interrupt.h"
|
|
|
|
|
|
static int write_file(const char *path, const char *str) {
|
|
int fd = 0;
|
|
|
|
if ((fd = open(path, O_WRONLY)) == 0) {
|
|
fprintf(stderr, "unable to open %s\n", path);
|
|
return 1;
|
|
}
|
|
|
|
if (write(fd, str, strlen(str)) < 1) {
|
|
fprintf(stderr, "unable to write to %s\n", path);
|
|
close(fd);
|
|
return 1;
|
|
}
|
|
|
|
close(fd);
|
|
return 0;
|
|
}
|
|
|
|
/* Register a sysfs GPIO pin to be interruptable
|
|
similar to:
|
|
$ echo 12 > /sys/class/gpio/export
|
|
$ echo both > /sys/class/gpio12/edge
|
|
$ echo in > /sys/class/gpio12/direction
|
|
|
|
*/
|
|
int int_register(int pin) {
|
|
|
|
char path[256];
|
|
char buffer[64];
|
|
|
|
/* begin by unregistering supplied pin, just in case */
|
|
(void) int_unregister(pin);
|
|
|
|
memset(buffer, 0, 64);
|
|
sprintf(buffer, "%d", pin);
|
|
if (write_file("/sys/class/gpio/export", buffer) != 0) {
|
|
return 1;
|
|
}
|
|
|
|
/* sleep 500 ms to let linux set up the dir .. */
|
|
usleep(500000);
|
|
|
|
memset(path, 0, 256);
|
|
sprintf(path, "%s%d/%s", "/sys/class/gpio/gpio", pin, "edge");
|
|
if (write_file(path, "both") != 0) {
|
|
return 1;
|
|
}
|
|
|
|
memset(path, 0, 256);
|
|
sprintf(path, "%s%d/%s", "/sys/class/gpio/gpio", pin, "direction");
|
|
if (write_file(path, "in") != 0) {
|
|
return 1;
|
|
}
|
|
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* unregister an interrupt gpio config
|
|
similar to:
|
|
$ echo 12 > /sys/class/gpio/unexport
|
|
*/
|
|
int int_unregister(int pin) {
|
|
char buffer[64];
|
|
|
|
memset(buffer, 0, 64);
|
|
sprintf(buffer, "%d", pin);
|
|
if (write_file("/sys/class/gpio/unexport", buffer) != 0) {
|
|
return 1;
|
|
}
|
|
|
|
usleep(50000); /* sleep 50 ms */
|
|
|
|
return 0;
|
|
}
|
|
|
|
/* poll a gpio pin for interrupt event
|
|
blocking
|
|
*/
|
|
int int_poll(int pin) {
|
|
int fd;
|
|
struct pollfd pfd;
|
|
char path[256];
|
|
char buf[16];
|
|
|
|
memset(path, 0, 256);
|
|
sprintf(path, "%s%d/%s", "/sys/class/gpio/gpio", pin, "value");
|
|
|
|
if ((fd = open(path, O_RDONLY)) == 0) {
|
|
fprintf(stderr, "unable to open %s\n", path);
|
|
return 1;
|
|
}
|
|
|
|
pfd.fd = fd;
|
|
pfd.events = POLLPRI | POLLERR;
|
|
|
|
lseek(fd, 0, SEEK_SET);
|
|
read(fd, buf, sizeof buf);
|
|
|
|
poll(&pfd, 1, -1);
|
|
|
|
lseek(fd, 0, SEEK_SET);
|
|
read(fd, buf, sizeof buf);
|
|
|
|
return 0;
|
|
}
|