Python，evdev，USB条形码阅读器:如何解码输入数据

Question

我有Datalogic Gryphon GFS4400 2D条形码扫描仪。我已经放入树莓派，它作为USB HID设备工作。我可以读取条形码，输出转到默认TTY。

我想创建一个在读取条形码时处理输出的服务。我正在使用python和evdev。

有人可以指出如何将输出转换为正确字符的正确方向吗？

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487800017702297980000411000000000000702407088651000000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KEY_xxx转换为正确的字符。如果我只过滤下降事件，我仍然不明白什么是KEY_KPn等。Evetest给出了这个：

$ 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)

任何帮助不胜感激！谢谢。

Answer 1

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)。这有一些简洁的功能：

• 它开箱即用，
• 它适用于任何应用程序，
• 它适用于任何操作系统。

读取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，然后将文本转换为击键。您的计算机唯一看到的是USB键盘扫描代码，您的操作系统将击键转换回文本。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盘映射(在 HID 中没有通用的方式来发送文本而不是键)。

为了克服这个问题，一些条形码扫描仪可以(ab)使用Windows输入子系统的功能，用户可以直接输入ASCII代码。启用该功能后，读卡器模拟在按住左键Alt键入十进制 ASCII 代码号。 这样，就没有对当前键盘映射的依赖(但这会使另一个依赖于 Windows 输入层)。

在这里，这就是发生的事情。首先，条形码按下NumLock键，以检索 Num Lock 的当前状态(它将收到Num Lock LED状态的切换)，以确保启用它。然后它发布一系列Alt新闻+数字新闻/发布+Alt发布。如果解码的话，它是：052、056、055、050等。52是十进制ASCII码，表示4，56表示8，55表示7，50表示2等。

如果您更改了阅读器的配置，则可以禁用此功能以使用给定的键盘映射返回到通常的输入键。条形码的配置通常通过扫描手册中的特殊条形码来实现。如果没有条形码手册，则应在网络上提供。大多数情况下，配置代码在给定品牌内是可互操作的。

Answer 2

这是一个字符设备，这意味着它是面向字节的，因此每个事件都提供 1 个字节(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)，您可以使用

ev1 = ""
ev1 = event.unicode

，然后将ev1, ev2,...追加为面向块的格式。 使用数组缓冲区追加单个事件字节

有关字符(字节)或块定向，请参阅 http://en.wikipedia.org/wiki/Device_file

您还可以检查 alpha Unicodeevent.unicode.isalpha()

http://www.stackoverflow.com/questions/14111381/how-to-make-pygame-print-input-from-user