title: Why am I getting a runtime error / key error "no device found for" empty device address?
body: <p>Why am I getting the following error message when executing uhd_fft GNU Radio script: </p>
  
  <pre><code>/opt/gnuradio-3.7.1git/bin$ uhd_fft 
  linux; GNU C++ version 4.6.3; Boost_104601; UHD_003.005.003-123-g1c391767
  
  Traceback (most recent call last):
    File "/opt/gnuradio-3.7.1git/bin/uhd_fft", line 341, in &lt;module&gt;
      main ()
    File "/opt/gnuradio-3.7.1git/bin/uhd_fft", line 337, in main
      app = stdgui2.stdapp(app_top_block, "UHD FFT", nstatus=1)
    File "/opt/gnuradio-3.7.1git/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 38, in __init__
      wx.App.__init__ (self, redirect=False)
    File "/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7981, in __init__
      self._BootstrapApp()
    File "/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode/wx/_core.py", line 7555, in _BootstrapApp
      return _core_.PyApp__BootstrapApp(*args, **kwargs)
    File "/opt/gnuradio-3.7.1git/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 42, in OnInit
      self._max_noutput_items)
    File "/opt/gnuradio-3.7.1git/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 64, in __init__
      self.panel = stdpanel (self, self, top_block_maker, max_nouts)
    File "/opt/gnuradio-3.7.1git/lib/python2.7/dist-packages/gnuradio/wxgui/stdgui2.py", line 86, in __init__
      self.top_block = top_block_maker (frame, self, vbox, sys.argv)
    File "/opt/gnuradio-3.7.1git/bin/uhd_fft", line 91, in __init__
      otw_format=options.wire_format, args=options.stream_args))
    File "/opt/gnuradio-3.7.1git/lib/python2.7/dist-packages/gnuradio/uhd/__init__.py", line 121, in constructor_interceptor
      return old_constructor(*args)
    File "/opt/gnuradio-3.7.1git/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py", line 1700, in make
      return _uhd_swig.usrp_source_make(*args)
  RuntimeError: LookupError: KeyError: No devices found for -----&gt;
  Empty Device Address
  </code></pre>
  
  <p>I'm using <a href="http://nuand.com/" rel="nofollow">BladeRF hardware</a> and followed <a href="http://nuand.com/forums/viewtopic.php?f=9&amp;t=2804" rel="nofollow">these instructions</a>. </p>
  
  <p>I have gone through the recommendations listed here but UHD_FFT still can't seem to find the BladeRF even though </p>
  
  <pre><code>ls -lrt /dev | grep blade
  crw-------  1 root root    180,   0 Aug 11 14:04 bladerf0
  </code></pre>
  
  <p>Why would my device not be found by UHD_FFT even though linux is aware of its existence ? </p>