从/dev/input获取实时信息

Question

我不确定这是否是这个问题的正确位置。我正在尝试从系统上的操纵杆/dev/input/js0获取轴位置值。如果我运行jstest /dev/input/js0，它会给我所有按钮和轴位置的实时反馈。

我正在尝试将这些信息输入到我的C程序中来控制伺服系统。有没有这样做的函数？我在编程中没有太多使用输入设备的经验，所以这对我来说都是新的。

Answer 1

这个页面：http://scaryreasoner.wordpress.com/2008/02/22/programming-joysticks-with-linux/写了一篇关于如何从/dev/input/js0读取信息的很好的文章

您从文件中读取的事件的格式记录在这里：https://www.kernel.org/doc/Documentation/input/input.txt。它是一个简单的结构，包含时间戳、事件类型和标识符以及值：

struct input_event {
    struct timeval time;
    unsigned short type;
    unsigned short code;
    unsigned int value;
};

Answer 2

您可以运行此python code来读取事件。

您还可以使用高级模块python-evdev。

#!/usr/bin/env python

import struct

infile_path = "/dev/input/js0"
EVENT_SIZE = struct.calcsize("llHHI")
file = open(infile_path, "rb")
event = file.read(EVENT_SIZE)
while event:
    print(struct.unpack("llHHI", event))
    (tv_sec, tv_usec, type, code, value) = struct.unpack("llHHI", event)
    event = file.read(EVENT_SIZE)

示例输出：

(73324490, 8454144, 55242, 1118, 25231360)
(73324490, 42008576, 55242, 1118, 58785792)
(73324490, 75563008, 55242, 1118, 92340224)
(73324490, 109117440, 55242, 1118, 125894656)
(73324490, 142671872, 55242, 1118, 159449088)
(73324490, 176226304, 55242, 1118, 193003520)
(73324490, 209780736, 55242, 1118, 226557952)
(73324490, 243335168, 55242, 1118, 8519680)
(73324490, 25296896, 55242, 1118, 42074112)
(73324490, 58884097, 55242, 1118, 75661313)
(73324490, 92405760, 55242, 1118, 109215745)
(73324490, 125992961, 55242, 1118, 142737408)
(73324490, 159514624, 55242, 1118, 176324609)
(73327790, 84041474, 58542, 1118, 84049919)
(73328030, 84044852, 58782, 1118, 84017152)
(73331790, 33749013, 62542, 1118, 33742256)
(73331790, 33736851, 62562, 1118, 33731108)
(73331830, 33723339, 62602, 1118, 33718273)
(73332090, 33723339, 62862, 1118, 33685504)

Answer 3

在kev的帖子上构建

从linux/joytick.h文件：

struct js_event {
    __u32 time;     /* event timestamp in milliseconds */
    __s16 value;    /* value */
    __u8 type;      /* event type */
    __u8 number;    /* axis/button number */
};

所以python format应该是：“LhBB”

infile_path = "/dev/input/js0"
EVENT_SIZE = struct.calcsize("LhBB")
file = open(infile_path, "rb")
event = file.read(EVENT_SIZE)
while event:
    print(struct.unpack("LhBB", event))
    (tv_msec,  value, type, number) = struct.unpack("LhBB", event)
    event = file.read(EVENT_SIZE)

XBOX One S控制器的输出示例：

// type=button, number=button number
//msec, value, type, number
(2114530, 1, 1, 0) // A pressed
(2114670, 0, 1, 0) // A released
(2116490, 1, 1, 1) // B pressed
(2116620, 0, 1, 1) // B released
(2117370, 1, 1, 2) // X pressed
(2117520, 0, 1, 2) // X released
(2118220, 1, 1, 3) // Y pressed
(2118360, 0, 1, 3) // Y released