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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 usrp
  25 from gnuradio import eng_notation
  26 import copy
  27 import sys
  28
  29 # from current dir
  30 from pick_bitrate import pick_rx_bitrate
  31 import ofdm
  32
  33 # /////////////////////////////////////////////////////////////////////////////
  34 #                              receive path
  35 # /////////////////////////////////////////////////////////////////////////////
  36
  37 class receive_path(gr.hier_block):
  38     def __init__(self, fg, rx_callback, options):
  39
  40         options = copy.copy(options)    # make a copy so we can destructively modify
  41
  42         self._verbose     = options.verbose
  43         self._log         = options.log
  44         self._rx_callback = rx_callback      # this callback is fired when there's a packet available
  45
  46         if 0:
  47
  48             chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
  49                                               2.0,                  # sampling rate
  50                                               bw,                   # midpoint of trans. band
  51                                               1*bw,               # width of trans. band
  52                                               gr.firdes.WIN_KAISER)   # filter type
  53         else:
  54             chan_coeffs = [ 1.0, 0.0, 0 ]
  55         self.chan_filt = gr.fft_filter_ccc(1, chan_coeffs)
  56
  57         self.ofdm_demod = ofdm.ofdm_demod(fg, options)
  58
  59         # receiver
  60         self.packet_receiver = \
  61             blks.demod_ofdm_pkts(fg,
  62                                  self.ofdm_demod,
  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         fg.connect(self.chan_filt, self.probe)
  72
  73         # Display some information about the setup
  74         if self._verbose:
  75             self._print_verbage()
  76
  77         fg.connect(self.chan_filt, self.packet_receiver)
  78         #fg.connect(self.chan_filt, gr.file_sink(gr.sizeof_gr_complex, "ofdmrx_chflt.dat"))
  79         gr.hier_block.__init__(self, fg, self.chan_filt, None)
  80
  81     def carrier_sensed(self):
  82         """
  83         Return True if we think carrier is present.
  84         """
  85         #return self.probe.level() > X
  86         return self.probe.unmuted()
  87
  88     def carrier_threshold(self):
  89         """
  90         Return current setting in dB.
  91         """
  92         return self.probe.threshold()
  93
  94     def set_carrier_threshold(self, threshold_in_db):
  95         """
  96         Set carrier threshold.
  97
  98         @param threshold_in_db: set detection threshold
  99         @type threshold_in_db:  float (dB)
 100         """
 101         self.probe.set_threshold(threshold_in_db)
 102
 103
 104     def add_options(normal, expert):
 105         """
 106         Adds receiver-specific options to the Options Parser
 107         """
 108         normal.add_option("-v", "--verbose", action="store_true", default=False)
 109         expert.add_option("", "--log", action="store_true", default=False,
 110                           help="Log all parts of flow graph to files (CAUTION: lots of data)")
 111
 112     # Make a static method to call before instantiation
 113     add_options = staticmethod(add_options)
 114
 115
 116     def _print_verbage(self):
 117         """
 118         Prints information about the receive path
 119         """
 120         print "Using RX d'board %s"    % (self.subdev.side_and_name(),)
 121         print "Rx gain:         %g"    % (self.gain,)
 122         print "modulation:      %s"    % (self._demod_class.__name__)
 123         print "bitrate:         %sb/s" % (eng_notation.num_to_str(self._bitrate))
 124         print "samples/symbol:  %3d"   % (self._samples_per_symbol)
 125         print "decim:           %3d"   % (self._decim)