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Diffstat (limited to 'gnuradio-examples/python/digital/receive_path.py')
| -rw-r--r-- | gnuradio-examples/python/digital/receive_path.py | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/gnuradio-examples/python/digital/receive_path.py b/gnuradio-examples/python/digital/receive_path.py new file mode 100644 index 000000000..9d55c88dd --- /dev/null +++ b/gnuradio-examples/python/digital/receive_path.py @@ -0,0 +1,252 @@ +#!/usr/bin/env python +# +# Copyright 2005,2006 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, blks +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.hier_block): + def __init__(self, fg, demod_class, rx_callback, options): + + 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() + + # 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 + 0.1, # 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 = \ + blks.demod_pkts(fg, + self._demod_class(fg, **demod_kwargs), + access_code=None, + callback=self._rx_callback, + threshold=-1) + + 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) + + 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 + + # Carrier Sensing Blocks + alpha = 0.001 + thresh = 30 # in dB, will have to adjust + self.probe = gr.probe_avg_mag_sqrd_c(thresh,alpha) + fg.connect(self.chan_filt, self.probe) + + # Display some information about the setup + if self._verbose: + self._print_verbage() + + fg.connect(self.u, self.chan_filt, self.packet_receiver) + gr.hier_block.__init__(self, fg, None, None) + + 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 "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)) + # print "Rx Frequency: %f" % (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") |