Linux编程控制硬件(5) ---- 操作USB手柄

时间：2010-10-09 来源：bluedrum

Andrew Haung [email protected] 转载请注明作者及联络方式学员项目需要用到JoyStick来远程控制云台。以前在用SDL在游戏中很简单的就可以控制。但是现在需要在Linux C下直接调用C来控制JoyStick。因此找了一些资料来看。象如下的USB手柄基本上插入LINUX的USB口即可运行 a

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Linux控制原理 Linux C控制JoyStick的比较简单，首先在JoyStick在Linux 安装好驱动后会在/dev/input生成js0.对其设备控制，就是读取相应的结构来判断用户输入哪一些指令. 当用户操作手柄时，驱动发送js_event的结构给应用程序以通知用户作了哪一些操作。js_event有如下定义

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

手柄按钮分布当按下1-4号键会发送type = 1 (Button),number = 0- 3的值按下 select 返回 type = 1,number = 8, 按下 start 返回 type = 1,number = 9 当按下左侧四个键.有两种情况，当按ANALOG键时（即红灯亮起）。它返回如下四个值 js_event 的type 为2.(AXIS). 上键/下键:number = 6，两者的区别在于value,上键按下value = -32767,松开等于 = 0. 下健按下value = 32767,松开等于 0 , 左/右键:number = 5两者的区别在于value,左键按下value = -32767,松开等于 = 0. 右健按下value = 32767,松开等于 0 当ANALOG键关闭时（即红灯灭时）. 上键/下键:number =1, 左/右键:number =0. 下面的转动控制杆相对比较复杂。左侧旋转杆,向上拨 type = 2,number = 1,value = -32767 向下拨 type = 2,number = 1,value = 32767 向左 type = 2,number = 2,value = -32767 向右 type = 2,number = 2,value = 32767 如果是偏于某个方向，即于返回最接近的键的值type/number，但是value有介于0到最大值之间。当选旋转时，相当于向系统传送一系列的value渐变的jse_event。右侧转动控制杆是向上type = 2,number = 2 ,value =-32767 向下拨 type = 2,number = 2,value = 32767 向左 type = 2,number = 3,value = -32767 向右 type = 2,number = 3,value = 32767 完整的控制代码这是从网上下载的演示代码，这是调整过后正确误的 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 */
};

struct wwvi_js_event {
    int button[11];
    int stick1_x;
    int stick1_y;
    int stick2_x;
    int stick2_y;
};

extern int open_joystick(char *joystick_device);
extern int read_joystick_event(struct js_event *jse);
extern void set_joystick_y_axis(int axis);
extern void set_joystick_x_axis(int axis);
extern void close_joystick();
extern int get_joystick_status(struct wwvi_js_event *wjse);

#endif

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;

    /* maybe ioctls to interrogate features here? */

    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);
}

int get_joystick_status(struct wwvi_js_event *wjse)
{
    int rc;
    struct js_event jse;
    if (joystick_fd < 0)
        return -1;

    // memset(wjse, 0, sizeof(*wjse));

    while ((rc = read_joystick_event(&jse) == 1)) {
        jse.type &= ~JS_EVENT_INIT; /* ignore synthetic events */
        if (jse.type == JS_EVENT_AXIS) {
            switch (jse.number) {
            case 0: wjse->stick1_x = jse.value;
                break;
            case 1: wjse->stick1_y = jse.value;
                break;
            case 2: wjse->stick2_x = jse.value;
                break;
            case 3: wjse->stick2_y = jse.value;
                break;
            default:
                break;
            }
        } else if (jse.type == JS_EVENT_BUTTON) {
            if (jse.number < 10) {
                switch (jse.value) {
                case 0:
                case 1: wjse->button[jse.number] = jse.value;
                    break;
                default:
                    break;
                }
            }
        }
    }
    // printf("%d\n", wjse->stick1_y);

    return 0;
}

#if 1
/* a little test program */
int main(int argc, char *argv[])
{
    int fd, rc;
    int done = 0;

    struct js_event jse;

    fd = open_joystick("/dev/js0");
    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);
        }
    }
}
#endif