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   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2005,2006 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 2, 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, blks
  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_block):
  33     def __init__(self, fg, demod_class, rx_callback, options):
  34
  35         options = copy.copy(options)    # make a copy so we can destructively modify
  36
  37         self._verbose            = options.verbose
  38         self._bitrate            = options.bitrate         # desired bit rate
  39         self._samples_per_symbol = options.samples_per_symbol  # desired samples/symbol
  40
  41         self._rx_callback   = rx_callback      # this callback is fired when there's a packet available
  42         self._demod_class   = demod_class      # the demodulator_class we're using
  43
  44         # Get demod_kwargs
  45         demod_kwargs = self._demod_class.extract_kwargs_from_options(options)
  46
  47         # Design filter to get actual channel we want
  48         sw_decim = 1
  49         chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
  50                                           sw_decim * self._samples_per_symbol, # sampling rate
  51                                           1.0,                  # midpoint of trans. band
  52                                           0.5,                  # width of trans. band
  53                                           gr.firdes.WIN_HANN)   # filter type
  54         self.channel_filter = gr.fft_filter_ccc(sw_decim, chan_coeffs)
  55
  56         # receiver
  57         self.packet_receiver = \
  58             blks.demod_pkts(fg,
  59                             self._demod_class(fg, **demod_kwargs),
  60                             access_code=None,
  61                             callback=self._rx_callback,
  62                             threshold=-1)
  63
  64         # Carrier Sensing Blocks
  65         alpha = 0.001
  66         thresh = 30   # in dB, will have to adjust
  67         self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha)
  68
  69         # Display some information about the setup
  70         if self._verbose:
  71             self._print_verbage()
  72
  73         # connect the channel input filter to the carrier power detector
  74         fg.connect(self.channel_filter, self.probe)
  75
  76         # connect channel filter to the packet receiver
  77         fg.connect(self.channel_filter, self.packet_receiver)
  78
  79         gr.hier_block.__init__(self, fg, self.channel_filter, None)
  80
  81     def bitrate(self):
  82         return self._bitrate
  83
  84     def samples_per_symbol(self):
  85         return self._samples_per_symbol
  86
  87     def carrier_sensed(self):
  88         """
  89         Return True if we think carrier is present.
  90         """
  91         #return self.probe.level() > X
  92         return self.probe.unmuted()
  93
  94     def carrier_threshold(self):
  95         """
  96         Return current setting in dB.
  97         """
  98         return self.probe.threshold()
  99
 100     def set_carrier_threshold(self, threshold_in_db):
 101         """
 102         Set carrier threshold.
 103
 104         @param threshold_in_db: set detection threshold
 105         @type threshold_in_db:  float (dB)
 106         """
 107         self.probe.set_threshold(threshold_in_db)
 108
 109
 110     def add_options(normal, expert):
 111         """
 112         Adds receiver-specific options to the Options Parser
 113         """
 114         if not normal.has_option("--bitrate"):
 115             normal.add_option("-r", "--bitrate", type="eng_float", default=100e3,
 116                               help="specify bitrate [default=%default].")
 117         normal.add_option("", "--show-rx-gain-range", action="store_true", default=False,
 118                           help="print min and max Rx gain available on selected daughterboard")
 119         normal.add_option("-v", "--verbose", action="store_true", default=False)
 120         expert.add_option("-S", "--samples-per-symbol", type="int", default=2,
 121                           help="set samples/symbol [default=%default]")
 122         expert.add_option("", "--log", action="store_true", default=False,
 123                           help="Log all parts of flow graph to files (CAUTION: lots of data)")
 124
 125     # Make a static method to call before instantiation
 126     add_options = staticmethod(add_options)
 127
 128
 129     def _print_verbage(self):
 130         """
 131         Prints information about the receive path
 132         """
 133         print "\nReceive Path:"
 134         print "modulation:      %s"    % (self._demod_class.__name__)
 135         print "bitrate:         %sb/s" % (eng_notation.num_to_str(self._bitrate))
 136         print "samples/symbol:  %3d"   % (self._samples_per_symbol)