title: Python reading from serial
body: <p>I'm trying to read data from an RFID (RMD6300) to Raspberry Pi 1 in python but after reading for 30-40 secs whitout interruptions it crashes with the following error message: </p>
  
  <blockquote>
    <p>Traceback (most recent call last):   File "tmp.py", line 7, in
    
        string = ser.read(20)   File "/usr/local/lib/python2.7/dist-packages/serial/serialposix.py", line
    501, in read
        'device reports readiness to read but returned no data ' serial.serialutil.SerialException: device reports readiness to read
    but returned no data (device disconnected or multiple access on port?)</p>
  </blockquote>
  
  <p>this is my code: </p>
  
  <pre><code>import serial
  ser = serial.Serial('/dev/ttyAMA0',9600, timeout=1)
  IDs = ["xxxxxxxxxx","xxxxxxxxxx"]
  while True:
      bool = False;
      string = ser.read(20)
      if len(string) == 0:
          print "Insert tag"
          continue
      else:
          for i in range(len(IDs)):
              for l in range(len(string)):
                  if IDs[i] in string:
                      print IDs[i]
                      bool = True
                      break
                   else:
                       string = string[1:]+string[0]
               if bool:
                   break
      if not bool:
          print "Not found"
  </code></pre>