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   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2005,2006,2007 Free Software Foundation, Inc.
   4 #
   5 # This file is part of GNU Radio
   6 #
   7 # GNU Radio is free software; you can redistribute it and/or modify
   8 # it under the terms of the GNU General Public License as published by
   9 # the Free Software Foundation; either version 3, or (at your option)
  10 # any later version.
  11 #
  12 # GNU Radio is distributed in the hope that it will be useful,
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 # GNU General Public License for more details.
  16 #
  17 # You should have received a copy of the GNU General Public License
  18 # along with GNU Radio; see the file COPYING.  If not, write to
  19 # the Free Software Foundation, Inc., 51 Franklin Street,
  20 # Boston, MA 02110-1301, USA.
  21 #
  22
  23 from gnuradio import gr, gru, blks2
  24 from gnuradio import eng_notation
  25 import copy
  26 import sys
  27
  28 # /////////////////////////////////////////////////////////////////////////////
  29 #                              receive path
  30 # /////////////////////////////////////////////////////////////////////////////
  31
  32 class receive_path(gr.hier_block2):
  33     def __init__(self, demod_class, rx_callback, options):
  34         gr.hier_block2.__init__(self, "receive_path",
  35                                 gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
  36                                 gr.io_signature(0, 0, 0))                    # Output signature
  37
  38
  39         options = copy.copy(options)    # make a copy so we can destructively modify
  40
  41         self._verbose            = options.verbose
  42         self._bitrate            = options.bitrate         # desired bit rate
  43         self._samples_per_symbol = options.samples_per_symbol  # desired samples/symbol
  44
  45         self._rx_callback   = rx_callback      # this callback is fired when there's a packet available
  46         self._demod_class   = demod_class      # the demodulator_class we're using
  47
  48         # Get demod_kwargs
  49         demod_kwargs = self._demod_class.extract_kwargs_from_options(options)
  50
  51         # Design filter to get actual channel we want
  52         sw_decim = 1
  53         chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
  54                                           sw_decim * self._samples_per_symbol, # sampling rate
  55                                           1.0,                  # midpoint of trans. band
  56                                           0.5,                  # width of trans. band
  57                                           gr.firdes.WIN_HANN)   # filter type
  58         self.channel_filter = gr.fft_filter_ccc(sw_decim, chan_coeffs)
  59
  60         # receiver
  61         self.packet_receiver = \
  62             blks2.demod_pkts(self._demod_class(**demod_kwargs),
  63                              access_code=None,
  64                              callback=self._rx_callback,
  65                              threshold=-1)
  66
  67         # Carrier Sensing Blocks
  68         alpha = 0.001
  69         thresh = 30   # in dB, will have to adjust
  70         self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha)
  71
  72         # Display some information about the setup
  73         if self._verbose:
  74             self._print_verbage()
  75
  76         # connect block input to channel filter
  77         self.connect(self, self.channel_filter)
  78
  79         # connect the channel input filter to the carrier power detector
  80         self.connect(self.channel_filter, self.probe)
  81
  82         # connect channel filter to the packet receiver
  83         self.connect(self.channel_filter, self.packet_receiver)
  84
  85     def bitrate(self):
  86         return self._bitrate
  87
  88     def samples_per_symbol(self):
  89         return self._samples_per_symbol
  90
  91     def carrier_sensed(self):
  92         """
  93         Return True if we think carrier is present.
  94         """
  95         #return self.probe.level() > X
  96         return self.probe.unmuted()
  97
  98     def carrier_threshold(self):
  99         """
 100         Return current setting in dB.
 101         """
 102         return self.probe.threshold()
 103
 104     def set_carrier_threshold(self, threshold_in_db):
 105         """
 106         Set carrier threshold.
 107
 108         @param threshold_in_db: set detection threshold
 109         @type threshold_in_db:  float (dB)
 110         """
 111         self.probe.set_threshold(threshold_in_db)
 112
 113
 114     def add_options(normal, expert):
 115         """
 116         Adds receiver-specific options to the Options Parser
 117         """
 118         if not normal.has_option("--bitrate"):
 119             normal.add_option("-r", "--bitrate", type="eng_float", default=100e3,
 120                               help="specify bitrate [default=%default].")
 121         normal.add_option("-v", "--verbose", action="store_true", default=False)
 122         expert.add_option("-S", "--samples-per-symbol", type="int", default=2,
 123                           help="set samples/symbol [default=%default]")
 124         expert.add_option("", "--log", action="store_true", default=False,
 125                           help="Log all parts of flow graph to files (CAUTION: lots of data)")
 126
 127     # Make a static method to call before instantiation
 128     add_options = staticmethod(add_options)
 129
 130
 131     def _print_verbage(self):
 132         """
 133         Prints information about the receive path
 134         """
 135         print "\nReceive Path:"
 136         print "modulation:      %s"    % (self._demod_class.__name__)
 137         print "bitrate:         %sb/s" % (eng_notation.num_to_str(self._bitrate))
 138         print "samples/symbol:  %3d"   % (self._samples_per_symbol)