title: can write to rs232 serial instrument but can't read from it
body: <p>I have an rs232 serial device and I am trying to read and write to it using
  python with pyVISA. I am able to write my commands to it using "write" but 
  I If I try to us "read" or "ask" I get a timeout error. </p>
  
  <p>I can read and write to it easily through labview or tera term but I can't read using python.</p>
  
  <p>Here is the python code that is not working:</p>
  
  <pre><code>import visa as v
  si = v.SerialInstrument("COM1", delay = 0.1)
  si.clear()
  si.timeout = 3 
  si.baud_rate = 9600 
  si.data_bits = 8
  si.stop_bits = 1
  
  command = '0'
  while command != 'end':
      rorw = raw_input('ask, read, or write? &gt;&gt;')
      command = raw_input('enter command code &gt;&gt;')
      if rorw == 'write':
          write1 = si.write(command)
          print write1
      elif rorw == 'read':
          read1 = si.read()
          print read1
      else:
          ask1 = si.ask(command)
          print ask
  </code></pre>