Python、evdev、usb条形码阅读器：如何解码输入数据

我有Datalogic Gryphon GFS4400二维条形码扫描仪。我已经把树莓pi和它的作品作为USB隐藏设备。我可以读取条形码，输出变为默认TTY

我想创建一个serivce，在读取条形码时处理输出。我正在使用python和evdev

有人能告诉我如何将输出转换为正确的字符吗？

Python脚本如下所示：

from evdev import InputDevice, categorize, ecodes

device = InputDevice("/dev/input/by-id/usb-Datalogic_ADC__Inc._Handheld_Barcode_Scanner_S_N_G17A58010-event-kbd") # my keyboard
for event in device.read_loop():
    if event.type == ecodes.EV_KEY:
        print(categorize(event))

当我运行脚本并读取一个条形码时，我得到以下输出：

key event at 1491586389.048072, 69 (KEY_NUMLOCK), down
key event at 1491586389.049084, 69 (KEY_NUMLOCK), up
key event at 1491586389.050085, 56 (KEY_LEFTALT), down
key event at 1491586389.051081, 82 (KEY_KP0), down
key event at 1491586389.052082, 82 (KEY_KP0), up
key event at 1491586389.052082, 76 (KEY_KP5), down
key event at 1491586389.053084, 76 (KEY_KP5), up
key event at 1491586389.053084, 80 (KEY_KP2), down
key event at 1491586389.054079, 80 (KEY_KP2), up
key event at 1491586389.055084, 56 (KEY_LEFTALT), up
key event at 1491586389.056080, 56 (KEY_LEFTALT), down
key event at 1491586389.057088, 82 (KEY_KP0), down
key event at 1491586389.058079, 82 (KEY_KP0), up
key event at 1491586389.058079, 76 (KEY_KP5), down
key event at 1491586389.059087, 76 (KEY_KP5), up
key event at 1491586389.059087, 77 (KEY_KP6), down
key event at 1491586389.060041, 77 (KEY_KP6), up
key event at 1491586389.061046, 56 (KEY_LEFTALT), up
key event at 1491586389.062036, 56 (KEY_LEFTALT), down
key event at 1491586389.063100, 82 (KEY_KP0), down
key event at 1491586389.098114, 56 (KEY_LEFTALT), up
key event at 1491586389.099104, 56 (KEY_LEFTALT), down
key event at 1491586389.100126, 82 (KEY_KP0), down
key event at 1491586389.101125, 82 (KEY_KP0), up
key event at 1491586389.101125, 76 (KEY_KP5), down
key event at 1491586389.102114, 76 (KEY_KP5), up
key event at 1491586389.103118, 76 (KEY_KP5), down
key event at 1491586389.104115, 76 (KEY_KP5), up
key event at 1491586389.105114, 56 (KEY_LEFTALT), up
key event at 1491586389.106111, 56 (KEY_LEFTALT), down
key event at 1491586389.107127, 82 (KEY_KP0), down
key event at 1491586389.108134, 82 (KEY_KP0), up
key event at 1491586389.108134, 76 (KEY_KP5), down
key event at 1491586389.109121, 76 (KEY_KP5), up
key event at 1491586389.128128, 76 (KEY_KP5), up
key event at 1491586389.128128, 82 (KEY_KP0), down
key event at 1491586389.129121, 82 (KEY_KP0), up
key event at 1491586389.130107, 56 (KEY_LEFTALT), up
key event at 1491586389.131113, 56 (KEY_LEFTALT), down
key event at 1491586389.132127, 82 (KEY_KP0), down
key event at 1491586389.133126, 82 (KEY_KP0), up
key event at 1491586389.133126, 76 (KEY_KP5), down
key event at 1491586389.134126, 76 (KEY_KP5), up
key event at 1491586389.134126, 71 (KEY_KP7), down
key event at 1491586389.135125, 71 (KEY_KP7), up
key event at 1491586389.136104, 56 (KEY_LEFTALT), up
key event at 1491586389.137125, 56 (KEY_LEFTALT), down
key event at 1491586389.138119, 82 (KEY_KP0), down
key event at 1491586389.139117, 82 (KEY_KP0), up
key event at 1491586389.139117, 76 (KEY_KP5), down
key event at 1491586389.175126, 82 (KEY_KP0), down
key event at 1491586389.176117, 82 (KEY_KP0), up
key event at 1491586389.176117, 75 (KEY_KP4), down
key event at 1491586389.177134, 75 (KEY_KP4), up
key event at 1491586389.177134, 72 (KEY_KP8), down
key event at 1491586389.178129, 72 (KEY_KP8), up
key event at 1491586389.179136, 56 (KEY_LEFTALT), up
key event at 1491586389.180126, 56 (KEY_LEFTALT), down
key event at 1491586389.181122, 82 (KEY_KP0), down
key event at 1491586389.182130, 82 (KEY_KP0), up
key event at 1491586389.182130, 76 (KEY_KP5), down
key event at 1491586389.183130, 76 (KEY_KP5), up
key event at 1491586389.183130, 80 (KEY_KP2), down
key event at 1491586389.184116, 80 (KEY_KP2), up
key event at 1491586389.185122, 56 (KEY_LEFTALT), up
key event at 1491586389.186116, 56 (KEY_LEFTALT), down
key event at 1491586389.187134, 82 (KEY_KP0), down
key event at 1491586389.188125, 82 (KEY_KP0), up
key event at 1491586389.188125, 75 (KEY_KP4), down
key event at 1491586389.189137, 75 (KEY_KP4), up
key event at 1491586389.189137, 73 (KEY_KP9), down
key event at 1491586389.190129, 73 (KEY_KP9), up
key event at 1491586389.191129, 56 (KEY_LEFTALT), up
key event at 1491586389.192116, 56 (KEY_LEFTALT), down
key event at 1491586389.193122, 82 (KEY_KP0), down
key event at 1491586389.194118, 82 (KEY_KP0), up
key event at 1491586389.194118, 75 (KEY_KP4), down
key event at 1491586389.195127, 75 (KEY_KP4), up
key event at 1491586389.195127, 73 (KEY_KP9), down
key event at 1491586389.248120, 82 (KEY_KP0), up
key event at 1491586389.248120, 75 (KEY_KP4), down
key event at 1491586389.249143, 75 (KEY_KP4), up
key event at 1491586389.249143, 72 (KEY_KP8), down
key event at 1491586389.250109, 72 (KEY_KP8), up
key event at 1491586389.251147, 56 (KEY_LEFTALT), up
key event at 1491586389.252130, 56 (KEY_LEFTALT), down
key event at 1491586389.253137, 82 (KEY_KP0), down
key event at 1491586389.254141, 82 (KEY_KP0), up
key event at 1491586389.254141, 75 (KEY_KP4), down
key event at 1491586389.255155, 75 (KEY_KP4), up
key event at 1491586389.255155, 72 (KEY_KP8), down
key event at 1491586389.256129, 72 (KEY_KP8), up
key event at 1491586389.257119, 56 (KEY_LEFTALT), up
key event at 1491586389.258122, 56 (KEY_LEFTALT), down
key event at 1491586389.259125, 82 (KEY_KP0), down
key event at 1491586389.260129, 82 (KEY_KP0), up
key event at 1491586389.260129, 75 (KEY_KP4), down
key event at 1491586389.261136, 75 (KEY_KP4), up
key event at 1491586389.261136, 72 (KEY_KP8), down
key event at 1491586389.262124, 72 (KEY_KP8), up
key event at 1491586389.263140, 56 (KEY_LEFTALT), up
key event at 1491586389.264135, 56 (KEY_LEFTALT), down
key event at 1491586389.265133, 82 (KEY_KP0), down
key event at 1491586389.266125, 82 (KEY_KP0), up
key event at 1491586389.266125, 75 (KEY_KP4), down
key event at 1491586389.267131, 75 (KEY_KP4), up
key event at 1491586389.267131, 72 (KEY_KP8), down
key event at 1491586389.303143, 76 (KEY_KP5), down
key event at 1491586389.304127, 76 (KEY_KP5), up
key event at 1491586389.305146, 76 (KEY_KP5), down
key event at 1491586389.306139, 76 (KEY_KP5), up
key event at 1491586389.307145, 56 (KEY_LEFTALT), up
key event at 1491586389.308130, 56 (KEY_LEFTALT), down
key event at 1491586389.309137, 82 (KEY_KP0), down
key event at 1491586389.310127, 82 (KEY_KP0), up
key event at 1491586389.310127, 75 (KEY_KP4), down
key event at 1491586389.311131, 75 (KEY_KP4), up
key event at 1491586389.311131, 72 (KEY_KP8), down
key event at 1491586389.312144, 72 (KEY_KP8), up
key event at 1491586389.313135, 56 (KEY_LEFTALT), up
key event at 1491586389.349137, 72 (KEY_KP8), up
key event at 1491586389.350136, 56 (KEY_LEFTALT), up
key event at 1491586389.351123, 56 (KEY_LEFTALT), down
key event at 1491586389.352150, 82 (KEY_KP0), down
key event at 1491586389.370200, 82 (KEY_KP0), down
key event at 1491586389.371148, 82 (KEY_KP0), up
key event at 1491586389.371148, 75 (KEY_KP4), down
key event at 1491586389.372156, 75 (KEY_KP4), up
key event at 1491586389.372156, 72 (KEY_KP8), down
key event at 1491586389.373147, 72 (KEY_KP8), up
key event at 1491586389.374121, 56 (KEY_LEFTALT), up
key event at 1491586389.375140, 56 (KEY_LEFTALT), down
key event at 1491586389.376138, 82 (KEY_KP0), down
key event at 1491586389.377147, 82 (KEY_KP0), up
key event at 1491586389.377147, 75 (KEY_KP4), down
key event at 1491586389.378058, 75 (KEY_KP4), up
key event at 1491586389.378058, 72 (KEY_KP8), down
key event at 1491586389.379141, 72 (KEY_KP8), up
key event at 1491586389.380119, 56 (KEY_LEFTALT), up
key event at 1491586389.381159, 28 (KEY_ENTER), down
key event at 1491586389.382118, 28 (KEY_ENTER), up
key event at 1491586389.384121, 69 (KEY_NUMLOCK), down
key event at 1491586389.385115, 69 (KEY_NUMLOCK), up

我不明白如何将密钥转换成正确的字符。如果我只过滤事件，我仍然不了解什么是关键的，等等。Evetest给出了以下信息：

$ evtest /dev/input/event0
Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x5f9 product 0x2216 version 0x110
Input device name: "Datalogic ADC, Inc. Handheld Barcode Scanner"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 1 (KEY_ESC)
    Event code 2 (KEY_1)
    Event code 3 (KEY_2)
    Event code 4 (KEY_3)
    Event code 5 (KEY_4)
    Event code 6 (KEY_5)
    Event code 7 (KEY_6)
    Event code 8 (KEY_7)
    Event code 9 (KEY_8)
    Event code 10 (KEY_9)
    Event code 11 (KEY_0)
    Event code 12 (KEY_MINUS)
    Event code 13 (KEY_EQUAL)
    Event code 14 (KEY_BACKSPACE)
    Event code 15 (KEY_TAB)
    Event code 16 (KEY_Q)
    Event code 17 (KEY_W)
    Event code 18 (KEY_E)
    Event code 19 (KEY_R)
    Event code 20 (KEY_T)
    Event code 21 (KEY_Y)
    Event code 22 (KEY_U)
    Event code 23 (KEY_I)
    Event code 24 (KEY_O)
    Event code 25 (KEY_P)
    Event code 26 (KEY_LEFTBRACE)
    Event code 27 (KEY_RIGHTBRACE)
    Event code 28 (KEY_ENTER)
    Event code 29 (KEY_LEFTCTRL)
    Event code 30 (KEY_A)
    Event code 31 (KEY_S)
    Event code 32 (KEY_D)
    Event code 33 (KEY_F)
    Event code 34 (KEY_G)
    Event code 35 (KEY_H)
    Event code 36 (KEY_J)
    Event code 37 (KEY_K)
    Event code 38 (KEY_L)
    Event code 39 (KEY_SEMICOLON)
    Event code 40 (KEY_APOSTROPHE)
    Event code 41 (KEY_GRAVE)
    Event code 42 (KEY_LEFTSHIFT)
    Event code 43 (KEY_BACKSLASH)
    Event code 44 (KEY_Z)
    Event code 45 (KEY_X)
    Event code 46 (KEY_C)
    Event code 47 (KEY_V)
    Event code 48 (KEY_B)
    Event code 49 (KEY_N)
    Event code 50 (KEY_M)
    Event code 51 (KEY_COMMA)
    Event code 52 (KEY_DOT)
    Event code 53 (KEY_SLASH)
    Event code 54 (KEY_RIGHTSHIFT)
    Event code 55 (KEY_KPASTERISK)
    Event code 56 (KEY_LEFTALT)
    Event code 57 (KEY_SPACE)
    Event code 58 (KEY_CAPSLOCK)
    Event code 59 (KEY_F1)
    Event code 60 (KEY_F2)
    Event code 61 (KEY_F3)
    Event code 62 (KEY_F4)
    Event code 63 (KEY_F5)
    Event code 64 (KEY_F6)
    Event code 65 (KEY_F7)
    Event code 66 (KEY_F8)
    Event code 67 (KEY_F9)
    Event code 68 (KEY_F10)
    Event code 69 (KEY_NUMLOCK)
    Event code 70 (KEY_SCROLLLOCK)
    Event code 71 (KEY_KP7)
    Event code 72 (KEY_KP8)
    Event code 73 (KEY_KP9)
    Event code 74 (KEY_KPMINUS)
    Event code 75 (KEY_KP4)
    Event code 76 (KEY_KP5)
    Event code 77 (KEY_KP6)
    Event code 78 (KEY_KPPLUS)
    Event code 79 (KEY_KP1)
    Event code 80 (KEY_KP2)
    Event code 81 (KEY_KP3)
    Event code 82 (KEY_KP0)
    Event code 83 (KEY_KPDOT)
    Event code 85 (KEY_ZENKAKUHANKAKU)
    Event code 86 (KEY_102ND)
    Event code 87 (KEY_F11)
    Event code 88 (KEY_F12)
    Event code 89 (KEY_RO)
    Event code 90 (KEY_KATAKANA)
    Event code 91 (KEY_HIRAGANA)
    Event code 92 (KEY_HENKAN)
    Event code 93 (KEY_KATAKANAHIRAGANA)
    Event code 94 (KEY_MUHENKAN)
    Event code 95 (KEY_KPJPCOMMA)
    Event code 96 (KEY_KPENTER)
    Event code 97 (KEY_RIGHTCTRL)
    Event code 98 (KEY_KPSLASH)
    Event code 99 (KEY_SYSRQ)
    Event code 100 (KEY_RIGHTALT)
    Event code 102 (KEY_HOME)
    Event code 103 (KEY_UP)
    Event code 104 (KEY_PAGEUP)
    Event code 105 (KEY_LEFT)
    Event code 106 (KEY_RIGHT)
    Event code 107 (KEY_END)
    Event code 108 (KEY_DOWN)
    Event code 109 (KEY_PAGEDOWN)
    Event code 110 (KEY_INSERT)
    Event code 111 (KEY_DELETE)
    Event code 113 (KEY_MUTE)
    Event code 114 (KEY_VOLUMEDOWN)
    Event code 115 (KEY_VOLUMEUP)
    Event code 116 (KEY_POWER)
    Event code 117 (KEY_KPEQUAL)
    Event code 119 (KEY_PAUSE)
    Event code 121 (KEY_KPCOMMA)
    Event code 122 (KEY_HANGUEL)
    Event code 123 (KEY_HANJA)
    Event code 124 (KEY_YEN)
    Event code 125 (KEY_LEFTMETA)
    Event code 126 (KEY_RIGHTMETA)
    Event code 127 (KEY_COMPOSE)
    Event code 128 (KEY_STOP)
    Event code 129 (KEY_AGAIN)
    Event code 130 (KEY_PROPS)
    Event code 131 (KEY_UNDO)
    Event code 132 (KEY_FRONT)
    Event code 133 (KEY_COPY)
    Event code 134 (KEY_OPEN)
    Event code 135 (KEY_PASTE)
    Event code 136 (KEY_FIND)
    Event code 137 (KEY_CUT)
    Event code 138 (KEY_HELP)
    Event code 140 (KEY_CALC)
    Event code 142 (KEY_SLEEP)
    Event code 150 (KEY_WWW)
    Event code 152 (KEY_SCREENLOCK)
    Event code 158 (KEY_BACK)
    Event code 159 (KEY_FORWARD)
    Event code 161 (KEY_EJECTCD)
    Event code 163 (KEY_NEXTSONG)
    Event code 164 (KEY_PLAYPAUSE)
    Event code 165 (KEY_PREVIOUSSONG)
    Event code 166 (KEY_STOPCD)
    Event code 173 (KEY_REFRESH)
    Event code 176 (KEY_EDIT)
    Event code 177 (KEY_SCROLLUP)
    Event code 178 (KEY_SCROLLDOWN)
    Event code 179 (KEY_KPLEFTPAREN)
    Event code 180 (KEY_KPRIGHTPAREN)
    Event code 183 (KEY_F13)
    Event code 184 (KEY_F14)
    Event code 185 (KEY_F15)
    Event code 186 (KEY_F16)
    Event code 187 (KEY_F17)
    Event code 188 (KEY_F18)
    Event code 189 (KEY_F19)
    Event code 190 (KEY_F20)
    Event code 191 (KEY_F21)
    Event code 192 (KEY_F22)
    Event code 193 (KEY_F23)
    Event code 194 (KEY_F24)
    Event code 240 (KEY_UNKNOWN)
  Event type 4 (EV_MSC)
    Event code 4 (MSC_SCAN)
  Event type 17 (EV_LED)
    Event code 0 (LED_NUML)
    Event code 1 (LED_CAPSL)
    Event code 2 (LED_SCROLLL)
    Event code 3 (LED_COMPOSE)
    Event code 4 (LED_KANA)
  Event type 20 (EV_REP)
Properties:
Testing ... (interrupt to exit)

感谢您的帮助！谢谢。

这是一个字符设备，意味着它是面向字节的，因此每个事件提供1字节（unicode UTF-8）的信息

要从条形码扫描仪生成的每个事件中获取unicode字母（1字节），可以使用

ev1 = ""
ev1 = event.unicode

然后将

ev1，ev2，…

附加到面向块的格式。使用数组缓冲区追加单个事件字节

有关字符（字节）或面向块的信息，请参见

您还可以检查alpha-unicode

event.unicode.isalpha（）

---

为了实现无人驾驶，USB条形码阅读器模拟HID设备（实际上是键盘）。这有一些简洁的特点：

• 它是开箱即用的
• 它适用于任何应用程序
• 它适用于任何操作系统

阅读器的默认行为只是模拟击键。他们读取代码，解码，将其转换为文本，然后将文本转换为按键。你的电脑只能看到USB键盘扫描码，你的操作系统会将按键转换回文本。这有一个主要缺点：它依赖于键盘语言映射设置，因此读者必须知道要使用什么键映射（没有通用的方式发送文本而不是HID中的键）

为了克服这个问题，一些条形码扫描仪可以（ab）使用Windows输入子系统的一个功能，用户可以直接输入ASCII码。当该功能启用时，读取器在按住左键的同时模拟键入十进制ASCII码。这样，就不依赖于当前的键盘映射（但这使得另一个依赖于Windows输入层）

这里，这就是发生的事情。首先，条形码发出一个按下

NumLock

键，以检索Num Lock的当前状态（它将收到一个打开

Num Lock LED

状态的开关），以确保启用它。然后它发出一系列的

Alt

press+numbers-press/release+

Alt

release。如果你解码它，它是：

052

，

056

，

055

，

050

，等等。

52

是十进制ASCII码，表示

4

，

56

表示

8

，

55

表示

7

，

50

表示

2

，等等

---

若您更改了阅读器的配置，您可能会禁用此功能，以便使用给定的键映射返回到常用的输入键。条形码的配置通常通过扫描手册中的特殊条形码进行。如果您没有条形码手册，则应在web上提供该手册。大多数情况下，配置代码在给定品牌内是可互操作的。

这对我有点帮助！现在我明白了，首先它说numlock打开，然后左alt向下，然后使用数字键盘0，5，2，也就是u+052=4。谢谢：）