title: arduino read in pyfirmata gives output as none
body: <p>I wrote a basic code for reading values from analog pin 0(I have a light sensor attached to it and the output is coming at analog pin 0) in python3 using pyfirmata, but it is giving the output as none no matter what. I tried the same code in arduino IDE and that is  giving the right answer. Please help.</p>
  
  <p>Code is :</p>
  
  <pre><code>from pyfirmata import Arduino, util
  import time
  board = Arduino('/dev/cu.usbmodem1411')
  
  it = util.Iterator(board)
  it.start()
  
  board.analog[0].enable_reporting()
  
  while True : 
              print (board.analog[0].read())
              time.sleep(1)    
  </code></pre>
  
  <p>Even when it gives an output after few seconds, it gives 0.29 which isn't actually the sensor value that comes on serial monitor. That value varies between 0 and 1023 and is relatively quite larger than this.</p>