Python, evdev, usb barcode reader: 如何解码输入数据
Python, evdev, usb barcode reader: how to decode the input data
我有 Datalogic Gryphon GFS4400 二维条码扫描器。我已经输入 Raspberry pi 并且它作为 USB HID 设备工作。我可以读取条形码并且输出为默认 TTY。
我想创建一个服务来处理读取条形码时的输出。我正在使用 python 和 evdev。
谁能给我指出正确的方向如何将输出转换为正确的字符？
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。如果我只过滤向下事件，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)
感谢任何帮助！谢谢。
这是一个字符设备意味着它是字节导向的，所以每个事件提供 1 个字节（unicode UTF-8）的资讯
要从条形码扫描仪生成的每个事件中获取一个 unicode 字母（1 字节），您可以使用
ev1 = ""
ev1 = event.unicode
然后将 ev1, ev2,... 附加到面向块的格式。使用数组缓冲区附加单个事件字节
面向字符（字节）或面向块的参见http://en.wikipedia.org/wiki/Device_file
您还可以检查 alpha unicode event.unicode.isalpha()
http://www.whosebug.com/questions/14111381/how-to-make-pygame-print-input-from-user
为了实现无驱动，USB 条形码 reader 模拟 HID 设备（实际上是键盘）。这有一些简洁的功能：
- 开箱即用，
- 它适用于任何应用程序，
- 它适用于任何 OS。
readers 的默认行为只是模拟击键。他们阅读代码、对其进行解码、将其转换为文本，然后将文本转换为击键。您的计算机只能看到 USB 键盘扫描代码，您的 OS 会将击键转换回文本。这有一个主要缺点：它依赖于键盘语言映射设置，因此 reader 必须知道要使用什么键盘映射（没有通用的方式来发送文本而不是 HID 中的键）。
为了克服这个问题，一些条形码扫描器可以（ab）使用 Windows 输入子系统的一个功能，用户可以在其中直接输入 ASCII 代码。启用该功能后，reader 模拟在按住左 Alt 键的同时键入十进制 ASCII 代码。这样，就不会依赖于当前的键盘映射（但这又依赖于 Windows 输入层）。
在这里，这就是发生的事情。首先，条形码按下 NumLock 键，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。然后它发出一系列Alt press + numbers press/release + Alt release。解码的话是：052、056、055、050等。52是4的十进制ASCII码， 56 代表 8，55 代表 7，50 代表 2，等等
如果您更改 reader 的配置，您可能可以禁用此功能以使用给定的键盘映射返回 常用 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进行。如果您没有，您的条形码手册应该可以在网上找到。大多数时候，配置代码在给定品牌内是可互操作的。
我有 Datalogic Gryphon GFS4400 二维条码扫描器。我已经输入 Raspberry pi 并且它作为 USB HID 设备工作。我可以读取条形码并且输出为默认 TTY。
我想创建一个服务来处理读取条形码时的输出。我正在使用 python 和 evdev。
谁能给我指出正确的方向如何将输出转换为正确的字符？
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。如果我只过滤向下事件，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)
感谢任何帮助！谢谢。
这是一个字符设备意味着它是字节导向的，所以每个事件提供 1 个字节（unicode UTF-8）的资讯
要从条形码扫描仪生成的每个事件中获取一个 unicode 字母（1 字节），您可以使用
ev1 = ""
ev1 = event.unicode
然后将 ev1, ev2,... 附加到面向块的格式。使用数组缓冲区附加单个事件字节
面向字符（字节）或面向块的参见http://en.wikipedia.org/wiki/Device_file
您还可以检查 alpha unicode event.unicode.isalpha()
http://www.whosebug.com/questions/14111381/how-to-make-pygame-print-input-from-user
为了实现无驱动，USB 条形码 reader 模拟 HID 设备（实际上是键盘）。这有一些简洁的功能：
- 开箱即用，
- 它适用于任何应用程序，
- 它适用于任何 OS。
readers 的默认行为只是模拟击键。他们阅读代码、对其进行解码、将其转换为文本，然后将文本转换为击键。您的计算机只能看到 USB 键盘扫描代码，您的 OS 会将击键转换回文本。这有一个主要缺点：它依赖于键盘语言映射设置，因此 reader 必须知道要使用什么键盘映射（没有通用的方式来发送文本而不是 HID 中的键）。
为了克服这个问题，一些条形码扫描器可以（ab）使用 Windows 输入子系统的一个功能，用户可以在其中直接输入 ASCII 代码。启用该功能后，reader 模拟在按住左 Alt 键的同时键入十进制 ASCII 代码。这样，就不会依赖于当前的键盘映射（但这又依赖于 Windows 输入层）。
在这里，这就是发生的事情。首先，条形码按下 NumLock 键，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。然后它发出一系列Alt press + numbers press/release + Alt release。解码的话是：052、056、055、050等。52是4的十进制ASCII码， 56 代表 8，55 代表 7，50 代表 2，等等
如果您更改 reader 的配置，您可能可以禁用此功能以使用给定的键盘映射返回 常用 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进行。如果您没有，您的条形码手册应该可以在网上找到。大多数时候，配置代码在给定品牌内是可互操作的。