raspberry pi + usb rfid card reader

ScanCardReader.py

# ScanCardReader.py
# -*- coding: utf-8 -*-
# scanning usb rfid card reader.

import evdev
from evdev import InputDevice, categorize, ecodes
from select import select

input = evdev.InputDevice('/dev/input/event0')

scancodes = {
    # Scancode: ASCIICode
    0: None, 1: u'ESC', 2: u'1', 3: u'2', 4: u'3', 5: u'4', 6: u'5', 7: u'6', 8: u'7', 9: u'8',
    10: u'9', 11: u'0', 12: u'-', 13: u'=', 14: u'BKSP', 15: u'TAB', 16: u'Q', 17: u'W', 18: u'E', 19: u'R',
    20: u'T', 21: u'Y', 22: u'U', 23: u'I', 24: u'O', 25: u'P', 26: u'[', 27: u']', 28: u'CRLF', 29: u'LCTRL',
    30: u'A', 31: u'S', 32: u'D', 33: u'F', 34: u'G', 35: u'H', 36: u'J', 37: u'K', 38: u'L', 39: u';',
    40: u'"', 41: u'`', 42: u'LSHFT', 43: u'\\', 44: u'Z', 45: u'X', 46: u'C', 47: u'V', 48: u'B', 49: u'N',
    50: u'M', 51: u',', 52: u'.', 53: u'/', 54: u'RSHFT', 56: u'LALT', 100: u'RALT'
}

# not working...
# issue: 一段時間沒使用，再次感應時，第一次會沒有反應
# https://github.com/gvalkov/python-evdev/issues/32
# https://github.com/gvalkov/python-evdev/issues/15      
buf = ''
while True:
  r, w, x = select([input], [], [], 0.1)
  if r:
    for event in input.read():
      if event.type == evdev.ecodes.EV_KEY and event.value == 1:
        data = evdev.categorize(event)
        key_lookup = scancodes.get(data.scancode) or 'UNKNOWN:{}'.format(data.scancode)
        if (key_lookup == 'CRLF'):
          print('scan:{}'.format(buf))
          buf = ''
        else:
          buf = buf + key_lookup