joystick.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>

#include "joystick.h"

static int joystick_fd = -1;

int open_joystick(char *joystick_device)
{
        joystick_fd = open(joystick_device, O_RDONLY | O_NONBLOCK); /* read write for force feedback? */

        if (joystick_fd < 0)
                return joystick_fd;

        return joystick_fd;
}

int read_joystick_event(struct js_event *jse)
{
        int bytes;

        bytes = read(joystick_fd, jse, sizeof(*jse));

        if (bytes == -1)
                return 0;

        if (bytes == sizeof(*jse))
                return 1;

        printf("Unexpected bytes from joystick:%d\n", bytes);

        return -1;
}

void close_joystick()
{
        close(joystick_fd);
}

/* a little test program */
int main(int argc, char *argv[])
{
    if (argc != 2) {
        exit(1);
    }

        int fd, rc;
        int done = 0;

        struct js_event jse;

        fd = open_joystick(argv[1]);

        if (fd < 0) {
                printf("open failed.\n");
                exit(1);
        }

        while (!done) {
                rc = read_joystick_event(&jse);
                usleep(1000);
                if (rc == 1) {
                        printf("Event: time %8u, value %8hd, type: %3u, axis/button: %u\n",
                                jse.time, jse.value, jse.type, jse.number);
                }
        }

    return 0;
}

joystick.h

/*
    (C) Copyright 2007,2008, Stephen M. Cameron.

    This file is part of wordwarvi.

    wordwarvi 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, or
    (at your option) any later version.

    wordwarvi is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with wordwarvi; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

 */
#include <stdio.h>
#ifndef __JOYSTICK_H__
#define __JOYSTICK_H__

#define JOYSTICK_DEVNAME "/dev/input/js0"

#define JS_EVENT_BUTTON         0x01    /* button pressed/released */
#define JS_EVENT_AXIS           0x02    /* joystick moved */
#define JS_EVENT_INIT           0x80    /* initial state of device */


struct js_event {
        unsigned int time;      /* event timestamp in milliseconds */
        short value;   /* value */
        unsigned char type;     /* event type */
        unsigned char number;   /* axis/button number */
};

extern int open_joystick(char *joystick_device);
extern int read_joystick_event(struct js_event *jse);
extern void close_joystick();

#endif