Andrew Haung 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
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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
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struct js_event {
unsigned int time; /* event timestamp in milliseconds */
short value; /* value */
unsigned char type; /* event type */
unsigned char number; /* axis/button number */
};
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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
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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
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/*
(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
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JoyStick.c
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#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
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