SimpleGPIO.c

/*
 * * SimpleGPIO.c
 * *
 * * Modifications by Derek Molloy, School of Electronic Engineering, DCU
 * * www.derekmolloy.ie
 * * Almost entirely based on Software by RidgeRun:
 * *
 * * Copyright (c) 2011, RidgeRun
 * * All rights reserved.
 * *
 * * 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 "header_files/SimpleGPIO.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>

/****************************************************************
 * * 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, PIN_DIRECTION out_flag)
{
	int fd;
	char buf[MAX_BUF];

	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 == OUTPUT_PIN)
		write(fd, "out", 4);
	else
		write(fd, "in", 3);

	close(fd);
	return 0;
}

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

	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==LOW)
		write(fd, "0", 2);
	else
		write(fd, "1", 2);

	close(fd);
	return 0;
}

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

	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;
	char buf[MAX_BUF];

	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;
	char buf[MAX_BUF];

	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);
}