157 lines
5.2 KiB
Python
Executable File
157 lines
5.2 KiB
Python
Executable File
#!/usr/bin/env python
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# -*- mode: Python -*-
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# Copyright 2011 Steve Glass
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#
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# This file is part of OP25.
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#
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# OP25 is free software; you can redistribute it and/or modify it
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# under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3, or (at your option)
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# any later version.
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#
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# OP25 is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
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# License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with OP25; see the file COPYING. If not, write to the Free
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# Software Foundation, Inc., 51 Franklin Street, Boston, MA
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# 02110-1301, USA.
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import cPickle
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import math
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import os
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import sys
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import threading
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from gnuradio import audio, gr, gru, op25, usrp
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from gnuradio.eng_option import eng_option
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from math import pi
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# The P25 receiver
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#
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class file_c4fm_rx (gr.top_block):
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# Initialize the P25 receiver
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#
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def __init__(self, filename, offset_freq, squelch):
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gr.top_block.__init__(self)
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# open file and info
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f = open(filename + ".info", "r")
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info = cPickle.load(f)
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capture_rate = info["capture-rate"]
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f.close()
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file = gr.file_source(gr.sizeof_gr_complex, filename, True)
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throttle = gr.throttle(gr.sizeof_gr_complex, capture_rate)
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self.connect(file, throttle)
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# setup receiver attributes
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channel_rate = 125000
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symbol_rate = 4800
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# channel filter
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self.channel_offset = offset_freq
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channel_decim = capture_rate // channel_rate
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channel_rate = capture_rate // channel_decim
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trans_width = 12.5e3 / 2;
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trans_centre = trans_width + (trans_width / 2)
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coeffs = gr.firdes.low_pass(1.0, capture_rate, trans_centre, trans_width, gr.firdes.WIN_HANN)
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self.channel_filter = gr.freq_xlating_fir_filter_ccf(channel_decim, coeffs, self.channel_offset, capture_rate)
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self.connect(throttle, self.channel_filter)
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# power squelch
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power_squelch = gr.pwr_squelch_cc(squelch, 1e-3, 0, True)
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self.connect(self.channel_filter, power_squelch)
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# FM demodulator
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self.symbol_deviation = 600.0
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fm_demod_gain = channel_rate / (2.0 * pi * self.symbol_deviation)
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fm_demod = gr.quadrature_demod_cf(fm_demod_gain)
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self.connect(power_squelch, fm_demod)
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# symbol filter
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symbol_decim = 1
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samples_per_symbol = channel_rate // symbol_rate
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symbol_coeffs = (1.0/samples_per_symbol,) * samples_per_symbol
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symbol_filter = gr.fir_filter_fff(symbol_decim, symbol_coeffs)
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self.connect(fm_demod, symbol_filter)
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# C4FM demodulator
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autotuneq = gr.msg_queue(2)
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self.demod_watcher = demod_watcher(autotuneq, self.adjust_channel_offset)
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demod_fsk4 = op25.fsk4_demod_ff(autotuneq, channel_rate, symbol_rate)
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self.connect(symbol_filter, demod_fsk4)
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# symbol slicer
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levels = [ -2.0, 0.0, 2.0, 4.0 ]
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slicer = op25.fsk4_slicer_fb(levels)
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self.connect(demod_fsk4, slicer)
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# frame decoder
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decoder = op25.decoder_bf()
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self.connect(slicer, decoder)
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# try to connect default output device
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try:
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audio_sink = audio.sink(8000, "plughw:0,0", True)
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self.connect(decoder, audio_sink)
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except Exception:
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sink = gr.null_sink(gr.sizeof_float)
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self.connect(decoder, sink)
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# Adjust the channel offset
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#
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def adjust_channel_offset(self, delta_hz):
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max_delta_hz = 12000.0
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delta_hz *= self.symbol_deviation
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delta_hz = max(delta_hz, -max_delta_hz)
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delta_hz = min(delta_hz, max_delta_hz)
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self.channel_filter.set_center_freq(self.channel_offset - delta_hz)
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# Demodulator frequency tracker
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#
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class demod_watcher(threading.Thread):
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def __init__(self, msgq, callback, **kwds):
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threading.Thread.__init__ (self, **kwds)
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self.setDaemon(1)
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self.msgq = msgq
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self.callback = callback
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self.keep_running = True
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self.start()
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def run(self):
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while(self.keep_running):
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msg = self.msgq.delete_head()
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frequency_correction = msg.arg1()
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self.callback(frequency_correction)
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# Run the receiver
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#
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if '__main__' == __name__:
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from optparse import OptionParser
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parser = OptionParser(option_class=eng_option)
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parser.add_option("-i", "--input-file", type="string", default=None, help="path to input file [=%default]")
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parser.add_option("-c", "--calibration", type="eng_float", default=0.0, help="channel frequency offset [=%default]", metavar="Hz")
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parser.add_option("-s", "--squelch", type="eng_float", default=15.0, help="squelch threshold [=%default]", metavar="dB")
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(options, args) = parser.parse_args()
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if len(args) != 0 or options.input_file is None:
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parser.print_help()
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sys.exit(1)
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self.options = options
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try:
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rx = file_c4fm_rx(options.input_file, options.calibration, options.squelch)
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rx.run()
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except KeyboardInterrupt:
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pass
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