Kontron KTAM3874-pITX - Manual (Page 66)

KTD-S0057-I Page 62 Linux® Programming Examples (DebianTM)
KTAM3874/pITX Software Guide
The program below generates a square wave (ratio of 1:1) as an output demonstration and subsequently it
reads the voltage level from the same pin as an input example (compiled on Ubuntu
TM distribution, needs
root rights).
/* GPIO test program
* Copyright (c) 2013 Kontron Technology A/S
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License.
*/
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#define MAX_GPIO 136
#define GPIO_IN 0
#define GPIO_OUT 1
#define DIR_OUT "out"
#define DIR_IN "in"
#define GP2_17 81 /* J2105 Pin 38 */
#define MAX_CNT 1000
#define SLP_TIME 100
static const char *dev_export = "/sys/class/gpio/export";
static const char *dev_unexport = "/sys/class/gpio/unexport";
static const char *dev_dir = "/sys/class/gpio/gpio%d/direction";
static const char *dev_val = "/sys/class/gpio/gpio%d/value";
static int fd [MAX_GPIO];
int gpio_export (int gpio_pin)
{
int
fd_tmp;
char str[8];
fd_tmp = open (dev_export, O_WRONLY);
if (fd_tmp < 0)
return -1;
sprintf (str, "%d", gpio_pin);
if (write (fd_tmp, str, strlen (str)) != strlen (str))
{
close (fd_tmp);
return -1;
}
close (fd_tmp);
return 0;
}