content: #!/usr/bin/env python
  
  from gnuradio import gr, filter
  from gnuradio import eng_notation
  from gnuradio.eng_option import eng_option
  from optparse import OptionParser
  
  try:
      import scipy
  except ImportError:
      print "Error: could not import scipy (http://www.scipy.org/)"
      sys.exit(1)
  
  try:
      import pylab
  except ImportError:
      print "Error: could not import pylab (http://matplotlib.sourceforge.net/)"
      sys.exit(1)
  
  class example_fir_filter_ccc(gr.top_block):
      def __init__(self, N, fs, bw, tw, atten, D):
          gr.top_block.__init__(self)
  
          self._nsamps = N
          self._fs = fs
          self._bw = bw
          self._tw = tw
          self._at = atten
          self._decim = D
          taps = filter.firdes.low_pass_2(1, self._fs, self._bw, self._tw, self._at)
          print "Num. Taps: ", len(taps)
  
          self.src  = gr.noise_source_c(gr.GR_GAUSSIAN, 1)
          self.head = gr.head(gr.sizeof_gr_complex, self._nsamps)
  
          self.filt0 = filter.fir_filter_ccc(self._decim, taps)
  
          self.vsnk_src = gr.vector_sink_c()
          self.vsnk_out = gr.vector_sink_c()
  
          self.connect(self.src, self.head, self.vsnk_src)
          self.connect(self.head, self.filt0, self.vsnk_out)
  
  def main():
      parser = OptionParser(option_class=eng_option, conflict_handler="resolve")
      parser.add_option("-N", "--nsamples", type="int", default=10000,
                        help="Number of samples to process [default=%default]")
      parser.add_option("-s", "--samplerate", type="eng_float", default=8000,
                        help="System sample rate [default=%default]")
      parser.add_option("-B", "--bandwidth", type="eng_float", default=1000,
                        help="Filter bandwidth [default=%default]")
      parser.add_option("-T", "--transition", type="eng_float", default=100,
                        help="Transition band [default=%default]")
      parser.add_option("-A", "--attenuation", type="eng_float", default=80,
                        help="Stopband attenuation [default=%default]")
      parser.add_option("-D", "--decimation", type="int", default=1,
                        help="Decmation factor [default=%default]")
      (options, args) = parser.parse_args ()
  
      put = example_fir_filter_ccc(options.nsamples,
                                   options.samplerate,
                                   options.bandwidth,
                                   options.transition,
                                   options.attenuation,
                                   options.decimation)
      put.run()
  
      data_src = scipy.array(put.vsnk_src.data())
      data_snk = scipy.array(put.vsnk_out.data())
  
      # Plot the signals PSDs
      nfft = 1024
      f1 = pylab.figure(1, figsize=(12,10))
      s1 = f1.add_subplot(1,1,1)
      s1.psd(data_src, NFFT=nfft, noverlap=nfft/4,
             Fs=options.samplerate)
      s1.psd(data_snk, NFFT=nfft, noverlap=nfft/4,
             Fs=options.samplerate)
  
      f2 = pylab.figure(2, figsize=(12,10))
      s2 = f2.add_subplot(1,1,1)
      s2.plot(data_src)
      s2.plot(data_snk.real, 'g')
  
      pylab.show()
      
  if __name__ == "__main__":
      try:
          main()
      except KeyboardInterrupt:
          pass
  
  