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#!/usr/bin/env python
#
# Copyright 2005-2007,2011 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
#
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING. If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#
from gnuradio import gr, gru
from gnuradio import eng_notation
from gnuradio import digital
import copy
import sys
# /////////////////////////////////////////////////////////////////////////////
# receive path
# /////////////////////////////////////////////////////////////////////////////
class receive_path(gr.hier_block2):
def __init__(self, demod_class, rx_callback, options):
gr.hier_block2.__init__(self, "receive_path",
gr.io_signature(1, 1, gr.sizeof_gr_complex),
gr.io_signature(0, 0, 0))
options = copy.copy(options) # make a copy so we can destructively modify
self._verbose = options.verbose
self._bitrate = options.bitrate # desired bit rate
self._rx_callback = rx_callback # this callback is fired when a packet arrives
self._demod_class = demod_class # the demodulator_class we're using
self._chbw_factor = options.chbw_factor # channel filter bandwidth factor
# Get demod_kwargs
demod_kwargs = self._demod_class.extract_kwargs_from_options(options)
# Build the demodulator
self.demodulator = self._demod_class(**demod_kwargs)
# Make sure the channel BW factor is between 1 and sps/2
# or the filter won't work.
if(self._chbw_factor < 1.0 or self._chbw_factor > self.samples_per_symbol()/2):
sys.stderr.write("Channel bandwidth factor ({0}) must be within the range [1.0, {1}].\n".format(self._chbw_factor, self.samples_per_symbol()/2))
sys.exit(1)
# Design filter to get actual channel we want
sw_decim = 1
chan_coeffs = gr.firdes.low_pass (1.0, # gain
sw_decim * self.samples_per_symbol(), # sampling rate
self._chbw_factor, # midpoint of trans. band
0.5, # width of trans. band
gr.firdes.WIN_HANN) # filter type
self.channel_filter = gr.fft_filter_ccc(sw_decim, chan_coeffs)
# receiver
self.packet_receiver = \
digital.demod_pkts(self.demodulator,
access_code=None,
callback=self._rx_callback,
threshold=-1)
# Carrier Sensing Blocks
alpha = 0.001
thresh = 30 # in dB, will have to adjust
self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha)
# Display some information about the setup
if self._verbose:
self._print_verbage()
# connect block input to channel filter
self.connect(self, self.channel_filter)
# connect the channel input filter to the carrier power detector
self.connect(self.channel_filter, self.probe)
# connect channel filter to the packet receiver
self.connect(self.channel_filter, self.packet_receiver)
def bitrate(self):
return self._bitrate
def samples_per_symbol(self):
return self.demodulator._samples_per_symbol
def differential(self):
return self.demodulator._differential
def carrier_sensed(self):
"""
Return True if we think carrier is present.
"""
#return self.probe.level() > X
return self.probe.unmuted()
def carrier_threshold(self):
"""
Return current setting in dB.
"""
return self.probe.threshold()
def set_carrier_threshold(self, threshold_in_db):
"""
Set carrier threshold.
@param threshold_in_db: set detection threshold
@type threshold_in_db: float (dB)
"""
self.probe.set_threshold(threshold_in_db)
def add_options(normal, expert):
"""
Adds receiver-specific options to the Options Parser
"""
if not normal.has_option("--bitrate"):
normal.add_option("-r", "--bitrate", type="eng_float", default=100e3,
help="specify bitrate [default=%default].")
normal.add_option("-v", "--verbose", action="store_true", default=False)
expert.add_option("-S", "--samples-per-symbol", type="float", default=2,
help="set samples/symbol [default=%default]")
expert.add_option("", "--log", action="store_true", default=False,
help="Log all parts of flow graph to files (CAUTION: lots of data)")
expert.add_option("", "--chbw-factor", type="float", default=1.0,
help="Channel bandwidth = chbw_factor x signal bandwidth [defaut=%default]")
# Make a static method to call before instantiation
add_options = staticmethod(add_options)
def _print_verbage(self):
"""
Prints information about the receive path
"""
print "\nReceive Path:"
print "modulation: %s" % (self._demod_class.__name__)
print "bitrate: %sb/s" % (eng_notation.num_to_str(self._bitrate))
print "samples/symbol: %.4f" % (self.samples_per_symbol())
print "Differential: %s" % (self.differential())
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