def OnScan(self, event):
    """ OMR form timing marks and their meaning:
    Col. #      Value
    -----------------
      1        Category labels
      2        Category mark
      3        Blank line
      4        Position labels
      5        Polition mark
      6        Row labels
      7-34     Pairwise comparison votes
         A total of 69 bytes are sent in a stream; the last is '\r' for end of record
    """
      
    # scanner row translations
    DATA_MAP_BLANK = {
      chr(32)+chr(32): 0
      }
    DATA_MAP_2 = {
      chr(32)+chr(36): 'nat',
      chr(96)+chr(32): 'eco',
      chr(36)+chr(32): 'soc'
      }
    DATA_MAP_5 = {
      chr(32)+chr(36): 'pro',
      chr(96)+chr(32): 'neu',
      chr(36)+chr(32): 'con'
      }
    DATA_MAP_7 = {
      chr(32)+chr(16): 1.000,    
      chr(32)+chr(8): 2.000,
      chr(32)+chr(4): 3.000,
      chr(32)+chr(2): 4.000,
      chr(32)+chr(1): 5.000,
      chr(64)+chr(32): 6.000,
      chr(16)+chr(32): 7.000,
      chr(8)+chr(32): 8.000,
      chr(4)+chr(32): 9.000,
      chr(34)+chr(8): 0.500,
      chr(34)+chr(4): 0.333,
      chr(34)+chr(2): 0.025,
      chr(34)+chr(1): 0.200,
      chr(66)+chr(32): 0.167,     
      chr(18)+chr(32): 0.143,
      chr(10)+chr(32): 0.125,
      chr(6)+chr(32): 0.111 
      }

    # Open serial port
    
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.open()
    if ser.isOpen() != True:
      serial.SerialException
    searchString = '\r'   # end of card read
    vote_id = 0           # card number incremented at start of read loop
    newStart = 0          # only > 0 if the run is aborted by the operator

    progressMax = 500
    omrDialog = wx.ProgressDialog("Scoping Form Input",
           "Processing ...", progressMax, style=wx.PD_CAN_ABORT |
           wx.PD_APP_MODAL | wx.PD_ELAPSED_TIME)
    keepGoing = True
    
    while True:
      vote_id += 1        # vote record number; heads list row & displayed for entry on form
      if newStart > 0:    # read was aborted (card mis-read? jammed?) and restarted
        vote_id = newStart
        omrDialog.Resume()

      # read the line sent by the OMR reader; record end is '\r'.
      line = ser.readline  # get all 69 bytes in one chunk

      """

      if value == DATA_MAP_BLANK:   # skip line if blank or labels
        continue
      if value == searchString:     # we're done with that form
        vrecord[:-1]               # slice off the terminal comma
        vrecord.append('\n')       # add a newline
        break

      vrecord.extend([line, ", "]) # add the pairwise comparison value, a comma, and a space

      Now I need to add that vote record to an array, and start a new row """

      while keepGoing and vote_id < progressMax:    # increment progress dialog
          if keepGoing == False:
            newStart = vote_id
            break
          keepGoing = omrDialog.Update(vote_id)
    
    # close the dialog box and serial port
    omrDialog.Destroy()
    ser.Close()