#!/usr/bin/env python
#
# Copyright 2005,2006,2007 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 2, 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, blks2
from gnuradio import usrp
from gnuradio import eng_notation
import copy
import sys
# from current dir
from pick_bitrate import pick_rx_bitrate
# /////////////////////////////////////////////////////////////////////////////
# receive path
# /////////////////////////////////////////////////////////////////////////////
class receive_path(gr.top_block):
def __init__(self, demod_class, rx_callback, options):
gr.top_block.__init__(self, "receive_path")
options = copy.copy(options) # make a copy so we can destructively modify
self._verbose = options.verbose
self._rx_freq = options.rx_freq # receiver's center frequency
self._rx_gain = options.rx_gain # receiver's gain
self._rx_subdev_spec = options.rx_subdev_spec # daughterboard to use
self._bitrate = options.bitrate # desired bit rate
self._decim = options.decim # Decimating rate for the USRP (prelim)
self._samples_per_symbol = options.samples_per_symbol # desired samples/symbol
self._fusb_block_size = options.fusb_block_size # usb info for USRP
self._fusb_nblocks = options.fusb_nblocks # usb info for USRP
self._rx_callback = rx_callback # this callback is fired when there's a packet available
self._demod_class = demod_class # the demodulator_class we're using
if self._rx_freq is None:
sys.stderr.write("-f FREQ or --freq FREQ or --rx-freq FREQ must be specified\n")
raise SystemExit
# Set up USRP source; also adjusts decim, samples_per_symbol, and bitrate
self._setup_usrp_source()
g = self.subdev.gain_range()
if options.show_rx_gain_range:
print "Rx Gain Range: minimum = %g, maximum = %g, step size = %g" \
% (g[0], g[1], g[2])
self.set_gain(options.rx_gain)
self.set_auto_tr(True) # enable Auto Transmit/Receive switching
# Set RF frequency
ok = self.set_freq(self._rx_freq)
if not ok:
print "Failed to set Rx frequency to %s" % (eng_notation.num_to_str(self._rx_freq))
raise ValueError, eng_notation.num_to_str(self._rx_freq)
# copy the final answers back into options for use by demodulator
options.samples_per_symbol = self._samples_per_symbol
options.bitrate = self._bitrate
options.decim = self._decim
# Get demod_kwargs
demod_kwargs = self._demod_class.extract_kwargs_from_options(options)
# 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
1.0, # midpoint of trans. band
0.5, # width of trans. band
gr.firdes.WIN_HANN) # filter type
# Decimating channel filter
# complex in and out, float taps
self.chan_filt = gr.fft_filter_ccc(sw_decim, chan_coeffs)
#self.chan_filt = gr.fir_filter_ccf(sw_decim, chan_coeffs)
# receiver
self.packet_receiver = \
blks2.demod_pkts(self._demod_class(**demod_kwargs),
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()
self.channel_filter = gr.fft_filter_ccc(sw_decim, chan_coeffs)
# connect the channel input filter to the carrier power detector
self.connect(self.u, self.channel_filter, self.probe)
# connect channel filter to the packet receiver
self.connect(self.channel_filter, self.packet_receiver)
def _setup_usrp_source(self):
self.u = usrp.source_c (fusb_block_size=self._fusb_block_size,
fusb_nblocks=self._fusb_nblocks)
adc_rate = self.u.adc_rate()
# derive values of bitrate, samples_per_symbol, and decim from desired info
(self._bitrate, self._samples_per_symbol, self._decim) = \
pick_rx_bitrate(self._bitrate, self._demod_class.bits_per_symbol(), \
self._samples_per_symbol, self._decim, adc_rate)
self.u.set_decim_rate(self._decim)
# determine the daughterboard subdevice we're using
if self._rx_subdev_spec is None:
self._rx_subdev_spec = usrp.pick_rx_subdevice(self.u)
self.subdev = usrp.selected_subdev(self.u, self._rx_subdev_spec)
self.u.set_mux(usrp.determine_rx_mux_value(self.u, self._rx_subdev_spec))
def set_freq(self, target_freq):
"""
Set the center frequency we're interested in.
@param target_freq: frequency in Hz
@rypte: bool
Tuning is a two step process. First we ask the front-end to
tune as close to the desired frequency as it can. Then we use
the result of that operation and our target_frequency to
determine the value for the digital up converter.
"""
r = self.u.tune(0, self.subdev, target_freq)
if r:
return True
return False
def set_gain(self, gain):
"""
Sets the analog gain in the USRP
"""
if gain is None:
r = self.subdev.gain_range()
gain = (r[0] + r[1])/2 # set gain to midpoint
self.gain = gain
return self.subdev.set_gain(gain)
def set_auto_tr(self, enable):
return self.subdev.set_auto_tr(enable)
def bitrate(self):
return self._bitrate
def samples_per_symbol(self):
return self._samples_per_symbol
def decim(self):
return self._decim
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
"""
add_freq_option(normal)
if not normal.has_option("--bitrate"):
normal.add_option("-r", "--bitrate", type="eng_float", default=None,
help="specify bitrate. samples-per-symbol and interp/decim will be derived.")
normal.add_option("-R", "--rx-subdev-spec", type="subdev", default=None,
help="select USRP Rx side A or B")
normal.add_option("", "--rx-gain", type="eng_float", default=None, metavar="GAIN",
help="set receiver gain in dB [default=midpoint]. See also --show-rx-gain-range")
normal.add_option("", "--show-rx-gain-range", action="store_true", default=False,
help="print min and max Rx gain available on selected daughterboard")
normal.add_option("-v", "--verbose", action="store_true", default=False)
expert.add_option("-S", "--samples-per-symbol", type="int", default=None,
help="set samples/symbol [default=%default]")
expert.add_option("", "--rx-freq", type="eng_float", default=None,
help="set Rx frequency to FREQ [default=%default]", metavar="FREQ")
expert.add_option("-d", "--decim", type="intx", default=None,
help="set fpga decimation rate to DECIM [default=%default]")
expert.add_option("", "--log", action="store_true", default=False,
help="Log all parts of flow graph to files (CAUTION: lots of data)")
# 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 "Using RX d'board %s" % (self.subdev.side_and_name(),)
print "Rx gain: %g" % (self.gain,)
print "modulation: %s" % (self._demod_class.__name__)
print "bitrate: %sb/s" % (eng_notation.num_to_str(self._bitrate))
print "samples/symbol: %3d" % (self._samples_per_symbol)
print "decim: %3d" % (self._decim)
print "Rx Frequency: %s" % (eng_notation.num_to_str(self._rx_freq))
def add_freq_option(parser):
"""
Hackery that has the -f / --freq option set both tx_freq and rx_freq
"""
def freq_callback(option, opt_str, value, parser):
parser.values.rx_freq = value
parser.values.tx_freq = value
if not parser.has_option('--freq'):
parser.add_option('-f', '--freq', type="eng_float",
action="callback", callback=freq_callback,
help="set Tx and/or Rx frequency to FREQ [default=%default]",
metavar="FREQ")