title: Python pyVISA GPIB connection issue
body: <p>I'm trying to connect to a GPIB instrument using pyVISA but I get an error.  I'm following the simple example on the pyVISA website: <a href="http://pyvisa.readthedocs.org/en/master/" rel="nofollow">http://pyvisa.readthedocs.org/en/master/</a> </p>
  
  <p>I type the following code into the IPython console:</p>
  
  <pre><code>import visa
  rm = visa.ResourceManager()
  rm.list_resources()
  
  Out[4]:
  (u'USB0::0x0957::0x0D0B::MY49431510::INSTR',
   u'USB0::0x0957::0x17BC::MY52400338::INSTR',
   u'ASRL1::INSTR',
   u'ASRL2::INSTR',
   u'ASRL5::INSTR',
   u'ASRL6::INSTR',
   u'ASRL7::INSTR',
   u'ASRL8::INSTR',
   u'ASRL9::INSTR',
   u'ASRL10::INSTR')
  </code></pre>
  
  <p>However, my GPIB instruments do not show up, just the serial ports and my USB instruments.  When I launch the Agilent Connection Expert (or NI MAX) I can see all my GPIB instruments and can communicate with them.  I also am able to communicate with the instruments without issue with Matlab.</p>
  
  <p>So when I try and connect to the instrument with the line:</p>
  
  <pre><code>inst = rm.open_resource('GPIB0::19::INSTR')
  </code></pre>
  
  <p>It throws an error:
   <code>VisaIOError: VI_ERROR_INTF_NUM_NCONFIG (-1073807195): The interface type is valid but the specified interface number is not configured.</code></p>
  
  <p>I've also tried to connect with the USB instruments that show up when I list the resources and they do not throw this error.  However, when I try and do a simple query:</p>
  
  <pre><code>inst = rm.open_resource('USB0::0x0957::0x0D0B::MY49431510::INSTR')
  inst.query("*IDN?")
  </code></pre>
  
  <p>Nothing gets returned and no errors get thrown.</p>
  
  <p>I'm using Python(X,Y) 2.7.9.0 with Python version 2.7.9 32 bit </p>
  
  <p>pyVISA version is 1.6.3
  NI bitness is 32</p>
  
  <p>Any guidance is appreciated as I'm new to Python.</p>
  
  <p>Thanks</p>