https://developer.ridgerun.com/wiki/index.php/How_to_use_GPIO_signals
https://developer.ridgerun.com/wiki/index.php?title=Gpio-int-test.c
Gpio-int-test.c:
/* Copyright (c) 2011, RidgeRun
* All rights reserved.
*
* Contributors include:
* Todd Fischer
* Brad Lu
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the RidgeRun.
* 4. Neither the name of the RidgeRun nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY RIDGERUN ''AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL RIDGERUN BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#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;
if (argc < 2) {
printf("Usage: gpio-int <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, "rising");
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);
}
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;
}离线
可以设置 上升沿/下降沿/两个都有 触发
可以监控多个GPIO
轮询时间间隔默认3秒,可以自行调整.
离线