git.gag.com Git - debian/gnuradio/blob - gnuradio-examples/python/digital/receive_path.py

   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2005,2006,2007,2009 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 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 usrp_options
  32
  33 # /////////////////////////////////////////////////////////////////////////////
  34 #                              receive path
  35 # /////////////////////////////////////////////////////////////////////////////
  36
  37 class receive_path(gr.hier_block2):
  38     def __init__(self, demod_class, rx_callback, options):
  39
  40         gr.hier_block2.__init__(self, "receive_path",
  41                                 gr.io_signature(0, 0, 0), # Input signature
  42                                 gr.io_signature(0, 0, 0)) # Output signature
  43
  44         options = copy.copy(options)    # make a copy so we can destructively modify
  45
  46         self._verbose            = options.verbose
  47         self._rx_freq            = options.rx_freq         # receiver's center frequency
  48         self._bitrate            = options.bitrate         # desired bit rate
  49         self._decim              = options.decim           # Decimating rate for the USRP (prelim)
  50         self._samples_per_symbol = options.samples_per_symbol  # desired samples/symbol
  51
  52         self._rx_callback   = rx_callback      # this callback is fired when there's a packet available
  53         self._demod_class   = demod_class      # the demodulator_class we're using
  54
  55         if self._rx_freq is None:
  56             sys.stderr.write("-f FREQ or --freq FREQ or --rx-freq FREQ must be specified\n")
  57             raise SystemExit
  58
  59         # Set up USRP source; also adjusts decim, samples_per_symbol, and bitrate
  60         self._setup_usrp_source(options)
  61
  62         # Set RF frequency
  63         ok = self.set_freq(self._rx_freq)
  64         if not ok:
  65             print "Failed to set Rx frequency to %s" % (eng_notation.num_to_str(self._rx_freq))
  66             raise ValueError, eng_notation.num_to_str(self._rx_freq)
  67
  68         # copy the final answers back into options for use by demodulator
  69         options.samples_per_symbol = self._samples_per_symbol
  70         options.bitrate = self._bitrate
  71         options.decim = self._decim
  72
  73         # Get demod_kwargs
  74         demod_kwargs = self._demod_class.extract_kwargs_from_options(options)
  75
  76         # Design filter to get actual channel we want
  77         sw_decim = 1
  78         chan_coeffs = gr.firdes.low_pass (1.0,                  # gain
  79                                           sw_decim * self._samples_per_symbol, # sampling rate
  80                                           1.0,                  # midpoint of trans. band
  81                                           0.5,                  # width of trans. band
  82                                           gr.firdes.WIN_HANN)   # filter type
  83
  84         # Decimating channel filter
  85         # complex in and out, float taps
  86         self.chan_filt = gr.fft_filter_ccc(sw_decim, chan_coeffs)
  87         #self.chan_filt = gr.fir_filter_ccf(sw_decim, chan_coeffs)
  88
  89         # receiver
  90         self.packet_receiver = \
  91             blks2.demod_pkts(self._demod_class(**demod_kwargs),
  92                              access_code=None,
  93                              callback=self._rx_callback,
  94                              threshold=-1)
  95
  96         # Carrier Sensing Blocks
  97         alpha = 0.001
  98         thresh = 30   # in dB, will have to adjust
  99
 100         if options.log_rx_power == True:
 101             self.probe = gr.probe_avg_mag_sqrd_cf(thresh,alpha)
 102             self.power_sink = gr.file_sink(gr.sizeof_float, "rxpower.dat")
 103             self.connect(self.chan_filt, self.probe, self.power_sink)
 104         else:
 105             self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha)
 106             self.connect(self.chan_filt, self.probe)
 107
 108         # Display some information about the setup
 109         if self._verbose:
 110             self._print_verbage()
 111
 112         self.connect(self.u, self.chan_filt, self.packet_receiver)
 113
 114     def _setup_usrp_source(self, options):
 115
 116         self.u = usrp_options.create_usrp_source(options)
 117         adc_rate = self.u.adc_rate()
 118
 119         # derive values of bitrate, samples_per_symbol, and decim from desired info
 120         (self._bitrate, self._samples_per_symbol, self._decim) = \
 121             pick_rx_bitrate(self._bitrate, self._demod_class.bits_per_symbol(), \
 122                             self._samples_per_symbol, self._decim, adc_rate, self.u.get_decim_rates())
 123
 124         self.u.set_decim(self._decim)
 125
 126     def set_freq(self, target_freq):
 127         """
 128         Set the center frequency we're interested in.
 129
 130         @param target_freq: frequency in Hz
 131         @rypte: bool
 132
 133         Tuning is a two step process.  First we ask the front-end to
 134         tune as close to the desired frequency as it can.  Then we use
 135         the result of that operation and our target_frequency to
 136         determine the value for the digital up converter.
 137         """
 138         return self.u.set_center_freq(target_freq)
 139
 140     def bitrate(self):
 141         return self._bitrate
 142
 143     def samples_per_symbol(self):
 144         return self._samples_per_symbol
 145
 146     def decim(self):
 147         return self._decim
 148
 149     def carrier_sensed(self):
 150         """
 151         Return True if we think carrier is present.
 152         """
 153         #return self.probe.level() > X
 154         return self.probe.unmuted()
 155
 156     def carrier_threshold(self):
 157         """
 158         Return current setting in dB.
 159         """
 160         return self.probe.threshold()
 161
 162     def set_carrier_threshold(self, threshold_in_db):
 163         """
 164         Set carrier threshold.
 165
 166         @param threshold_in_db: set detection threshold
 167         @type threshold_in_db:  float (dB)
 168         """
 169         self.probe.set_threshold(threshold_in_db)
 170
 171     @staticmethod
 172     def add_options(normal, expert):
 173         """
 174         Adds receiver-specific options to the Options Parser
 175         """
 176         add_freq_option(normal)
 177         if not normal.has_option("--bitrate"):
 178             normal.add_option("-r", "--bitrate", type="eng_float", default=None,
 179                               help="specify bitrate.  samples-per-symbol and interp/decim will be derived.")
 180         usrp_options.add_rx_options(normal)
 181         normal.add_option("-v", "--verbose", action="store_true", default=False)
 182         expert.add_option("-S", "--samples-per-symbol", type="int", default=None,
 183                           help="set samples/symbol [default=%default]")
 184         expert.add_option("", "--rx-freq", type="eng_float", default=None,
 185                           help="set Rx frequency to FREQ [default=%default]", metavar="FREQ")
 186         expert.add_option("", "--log", action="store_true", default=False,
 187                           help="Log all parts of flow graph to files (CAUTION: lots of data)")
 188         expert.add_option("", "--log-rx-power", action="store_true", default=False,
 189                           help="Log receive signal power to file (CAUTION: lots of data)")
 190
 191     def _print_verbage(self):
 192         """
 193         Prints information about the receive path
 194         """
 195         print "\nReceive Path:"
 196         print "USRP %s"    % (self.u,)
 197         print "Rx gain:         %g"    % (self.u.gain(),)
 198         print "modulation:      %s"    % (self._demod_class.__name__)
 199         print "bitrate:         %sb/s" % (eng_notation.num_to_str(self._bitrate))
 200         print "samples/symbol:  %3d"   % (self._samples_per_symbol)
 201         print "decim:           %3d"   % (self._decim)
 202         print "Rx Frequency:    %s"    % (eng_notation.num_to_str(self._rx_freq))
 203
 204 def add_freq_option(parser):
 205     """
 206     Hackery that has the -f / --freq option set both tx_freq and rx_freq
 207     """
 208     def freq_callback(option, opt_str, value, parser):
 209         parser.values.rx_freq = value
 210         parser.values.tx_freq = value
 211
 212     if not parser.has_option('--freq'):
 213         parser.add_option('-f', '--freq', type="eng_float",
 214                           action="callback", callback=freq_callback,
 215                           help="set Tx and/or Rx frequency to FREQ [default=%default]",
 216                           metavar="FREQ")