mspdebug/util/gpio.c

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/*
* C Implementation: gpio
*
* Description:
*
*
* Author: Paolo Zebelloni <p.zebelloni@c-labs-wt.com>, (C) 2014
*
* Copyright: See COPYING file that comes with this distribution
*
*/
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#include "gpio.h"
#include "output.h"
#ifdef __Windows__
/* Added for building on Windows
*
* Daniel Beer <dlbeer@gmail.com>, 3 Mar 2015
*/
int gpio_is_exported ( unsigned int gpio )
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
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int gpio_export ( unsigned int gpio )
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
int gpio_unexport ( unsigned int gpio )
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
int gpio_set_dir ( unsigned int gpio, unsigned int out_flag )
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
int gpio_set_value ( unsigned int gpio, unsigned int value )
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
int gpio_set_value_fd (int fd, int value)
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
int gpio_get_value ( unsigned int gpio )
{
return 0;
}
int gpio_get_value_fd (int fd, unsigned int gpio)
{
return 0;
}
int gpio_open_fd (unsigned int gpio)
{
printc_err("gpio: GPIO interface not supported on Windows\n");
return -1;
}
#else
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define SYSFS_GPIO_DIR "/sys/class/gpio"
#define MAX_BUF 64
/**
* @return 1 if the gpio is already exported, 0 otherwise, -1 on error
*/
int gpio_is_exported ( unsigned int gpio )
{
char dir_name[100] = {};
snprintf(dir_name, sizeof(dir_name) - 1, SYSFS_GPIO_DIR "/gpio%d", gpio);
struct stat s;
int err = stat(dir_name, &s);
if(-1 == err)
{
if(errno == ENOENT)
{
return 0;
} else {
return -1;
}
} else {
if(S_ISDIR(s.st_mode))
{
return 1;
} else {
return -1;
}
}
return -1;
}
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/**
* Before a Linux application can configure and use a GPIO, the GPIO first has to be exported to user.
* Each GPIO is not accessible from user space until the GPIO has been exported.
* You can only export a GPIO that isn't owned by a Linux kernel driver
* @param gpio GPIO number
* @return 0 if OK, -1 if fails
*/
int gpio_export ( unsigned int gpio )
{
int fd, len;
char buf[MAX_BUF];
fd = open ( SYSFS_GPIO_DIR "/export", O_WRONLY );
if ( fd < 0 )
{
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pr_error ( "gpio/export" );
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return -1;
}
len = snprintf ( buf, sizeof ( buf ), "%d", gpio );
write ( fd, buf, len );
close ( fd );
return 0;
}
/**
* Complement of gpio_export().
* @param gpio GPIO number
* @return 0 if OK, -1 if fails
*/
int gpio_unexport ( unsigned int gpio )
{
int fd, len;
char buf[MAX_BUF];
fd = open ( SYSFS_GPIO_DIR "/unexport", O_WRONLY );
if ( fd < 0 )
{
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pr_error ( "gpio/unexport" );
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return -1;
}
len = snprintf ( buf, sizeof ( buf ), "%d", gpio );
write ( fd, buf, len );
close ( fd );
return 0;
}
/**
* To avoid hardware issues where two devices are driving the same signal, GPIOs default to be configured as an input.
* If you want to use the GPIO as an output, you need to change the configuration
* @param gpio GPIO number
* @param out_flag TRUE means OUT, FALSE means IN
* @return 0 if OK, -1 if fails
*/
int gpio_set_dir ( unsigned int gpio, unsigned int out_flag )
{
int fd;
char buf[MAX_BUF];
snprintf ( buf, MAX_BUF, SYSFS_GPIO_DIR "/gpio%d/direction", gpio );
fd = open ( buf, O_WRONLY );
if ( fd < 0 )
{
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pr_error ( "gpio/direction" );
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return -1;
}
if ( out_flag )
write ( fd, "out", 4 );
else
write ( fd, "in", 3 );
close ( fd );
return 0;
}
/**
* Set HI or LO state to GPIO (output) pin.
* @param gpio GPIO number
* @param value TRUE means HI, FALSE means LO
* @return 0 if OK, -1 if fails
*/
int gpio_set_value ( unsigned int gpio, unsigned int value )
{
int fd;
char buf[MAX_BUF];
snprintf ( buf, MAX_BUF, SYSFS_GPIO_DIR "/gpio%d/value", gpio );
fd = open ( buf, O_WRONLY );
if ( fd < 0 )
{
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pr_error ( "gpio/set-value" );
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return -1;
}
write ( fd, value ? "1" : "0", 2 );
close ( fd );
return 0;
}
/**
* Read state of GPIO (input) pin.
* @param gpio GPIO number
* @return 0 if LO, 1 if HI, -1 if fails
*/
int gpio_get_value ( unsigned int gpio )
{
int fd;
char buf[MAX_BUF];
char ch;
snprintf ( buf, MAX_BUF, SYSFS_GPIO_DIR "/gpio%d/value", gpio );
fd = open ( buf, O_RDONLY );
if ( fd < 0 )
{
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pr_error ( "gpio/get-value" );
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return -1;
}
read ( fd, &ch, 1 );
close ( fd );
return ( ch != '0' );
}
/**
* Opens GPIO (input/output) pin file descriptor
* @param gpio GPIO number
* @return file descriptor, -1 if fails
*/
int gpio_open_fd ( unsigned int gpio ) {
int fd;
char buf[MAX_BUF];
snprintf ( buf, MAX_BUF, SYSFS_GPIO_DIR "/gpio%d/value", gpio );
fd = open ( buf, O_RDWR );
if ( fd < 0 )
{
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pr_error ( "gpio/get-value" );
return -1;
}
return fd;
}
/**
* Sets GPIO (output) value with given file descriptor
* @param file descriptor
* @param gpio GPIO number
* @return 0 if OK, -1 if fails
*/
int gpio_set_value_fd (int fd, int value)
{
ssize_t ret;
char gpio_value = value + '0';
ret = write (fd, &gpio_value, 1);
if (ret != 1)
{
printf("Error setting value gpio\n");
return -1;
}
return 0;
}
/**
* Read state of GPIO (input) pin, with file descriptor
* @param file descriptor
* @param gpio GPIO number
* @return 0 if LO, 1 if HI, -1 if fails
*/
int gpio_get_value_fd (int fd, unsigned int gpio)
{
ssize_t ret;
char value;
ret = pread (fd, &value, 1, 0);
if (ret != 1)
{
printf("Error getting value of gpio %u\n", gpio);
return -1;
}
return value == '1';
}
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#endif