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improved FSK decode
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Big thanks to Andy Walls for the code, from the gnuradio mailing list:
http://lists.gnu.org/archive/html/discuss-gnuradio/2017-01/msg00070.html
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@robotastic
robotastic committed Jan 16, 2017
1 parent f83a9d3 commit b6b1c23
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Showing 3 changed files with 33 additions and 34 deletions.
2 changes: 2 additions & 0 deletions .gitignore
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Expand Up @@ -4,6 +4,8 @@ sys_*/
junk/
2015/
2016/
fake/
wmata/
CMakeFiles/
build/
debug/
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36 changes: 13 additions & 23 deletions trunk-recorder/recorders/p25_recorder.cc
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Expand Up @@ -155,16 +155,15 @@ BOOST_LOG_TRIVIAL(error) << "Size of LPF: " << dest.size();
// convert from radians such that signal is in -3/-1/+1/+3
rescale = gr::blocks::multiply_const_ff::make((1 / (pi / 4)));

// fm demodulator (needed in fsk4 case)
double fm_demod_gain = system_channel_rate / (2.0 * pi * symbol_deviation);
fm_demod = gr::analog::quadrature_demod_cf::make(fm_demod_gain);
BOOST_LOG_TRIVIAL(info) << "p25_recorder.cc: fm_demod gain - " << fm_demod_gain;

demod_agc = gr::analog::agc2_ff::make(0.1, 0.01, 1.0, 0.1);
pre_demod_agc = gr::analog::agc2_cc::make(0.1, 0.01, 1.0, 1.0);

super_agc = make_rx_agc_cc(system_channel_rate, true, -90, 0, 0, 500, true);

double freq_to_norm_radians = pi/(system_channel_rate/2.0);
double fc = 0.0;
double fd = 600.0;
double pll_demod_gain = 1.0/(fd*freq_to_norm_radians);
pll_freq_lock = gr::analog::pll_freqdet_cf::make ( (symbol_rate/2.0*1.2)*freq_to_norm_radians, (fc+(3*fd*1.9))*freq_to_norm_radians, (fc+(-3*fd*1.9))*freq_to_norm_radians);
pll_amp = gr::blocks::multiply_const_ff::make(pll_demod_gain);

baseband_noise_filter_taps = gr::filter::firdes::low_pass_2(1.0, system_channel_rate, symbol_rate/2.0*1.175, symbol_rate/2.0*0.125, 20.0, gr::filter::firdes::WIN_KAISER, 6.76);
noise_filter = gr::filter::fft_filter_fff::make(1.0, baseband_noise_filter_taps);
double symbol_decim = 1;

valve = gr::blocks::copy::make(sizeof(gr_complex));
Expand Down Expand Up @@ -215,10 +214,10 @@ BOOST_LOG_TRIVIAL(error) << "Size of LPF: " << dest.size();
connect(self(), 0, valve, 0);
connect(valve, 0, prefilter, 0);
connect(prefilter, 0, arb_resampler, 0);
connect(arb_resampler, 0, pre_demod_agc, 0);
connect(pre_demod_agc, 0,fm_demod, 0);
connect(fm_demod, 0, baseband_amp, 0);
connect(baseband_amp, 0, sym_filter, 0);
connect(arb_resampler, 0, pll_freq_lock, 0);
connect(pll_freq_lock, 0, pll_amp, 0);
connect(pll_amp, 0, noise_filter, 0);
connect(noise_filter, 0, sym_filter, 0);
connect(sym_filter, 0, fsk4_demod, 0);
connect(fsk4_demod, 0, slicer, 0);
connect(slicer, 0, op25_frame_assembler, 0);
Expand All @@ -229,25 +228,16 @@ BOOST_LOG_TRIVIAL(error) << "Size of LPF: " << dest.size();
connect(self(), 0, valve, 0);
connect(valve, 0, prefilter, 0);
connect(prefilter, 0, arb_resampler, 0);

// connect(prefilter, 0, tagger,0);
// connect(tagger,0, arb_resampler, 0);
connect(arb_resampler, 0, agc, 0);
connect(agc, 0, costas_clock, 0);
connect(costas_clock, 0, diffdec, 0);
connect(diffdec, 0, to_float, 0);
connect(to_float, 0, rescale, 0);
connect(rescale, 0, slicer, 0);
connect(slicer, 0, op25_frame_assembler, 0);

// connect(slicer,0, active_probe,0);
// connect(active_probe,0, op25_frame_assembler,0);
connect(op25_frame_assembler, 0, converter, 0);
connect(converter, 0, multiplier, 0);
connect(multiplier, 0, wav_sink, 0);

// connect(converter, 0, last_probe,0);
// connect(last_probe,0, wav_sink,0);
}
}

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29 changes: 18 additions & 11 deletions trunk-recorder/recorders/p25_recorder.h
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Expand Up @@ -21,16 +21,15 @@
#include <gnuradio/filter/firdes.h>
#include <gnuradio/filter/fir_filter_ccf.h>
#include <gnuradio/filter/fir_filter_fff.h>
#include <gnuradio/filter/fft_filter_fff.h>
#include <gnuradio/filter/freq_xlating_fir_filter_ccf.h>
#include <gnuradio/filter/firdes.h>
#include <gnuradio/filter/rational_resampler_base_ccc.h>

#include <gnuradio/analog/quadrature_demod_cf.h>

#include <gnuradio/analog/sig_source_c.h>
#include <gnuradio/analog/feedforward_agc_cc.h>
#include <gnuradio/analog/agc2_ff.h>
#include <gnuradio/analog/agc2_cc.h>
#include <gnuradio/analog/pll_freqdet_cf.h>
#include <gnuradio/digital/diff_phasor_cc.h>

#include <gnuradio/blocks/complex_to_arg.h>
Expand All @@ -53,9 +52,17 @@
#include <gnuradio/blocks/short_to_float.h>
#include <gnuradio/blocks/char_to_float.h>

#include <op25_repeater/fsk4_demod_ff.h>
/*#include <op25_repeater/fsk4_demod_ff.h>
#include <op25_repeater/fsk4_slicer_fb.h>
#include <op25_repeater/p25_frame_assembler.h>
#include <op25_repeater/gardner_costas_cc.h>
#include <op25_repeater/vocoder.h>*/


#include "../../op25_repeater/include/op25_repeater/fsk4_demod_ff.h"
#include <op25_repeater/fsk4_slicer_fb.h>
#include "../../op25_repeater/include/op25_repeater/p25_frame_assembler.h"

#include <op25_repeater/gardner_costas_cc.h>
#include <op25_repeater/vocoder.h>
#include <gnuradio/msg_queue.h>
Expand All @@ -70,9 +77,6 @@
#include "../../gr_blocks/latency_probe.h"
#include "../../gr_blocks/latency_tagger.h"


#include "../../gr_blocks/rx_agc_cc.h"

class Source;
class p25_recorder;
typedef boost::shared_ptr<p25_recorder> p25_recorder_sptr;
Expand Down Expand Up @@ -131,6 +135,8 @@ class p25_recorder : public gr::hier_block2, public Recorder
std::vector<float> lpf_coeffs;
std::vector<float> arb_taps;
std::vector<float> sym_taps;
std::vector<float> baseband_noise_filter_taps;


//gr::filter::freq_xlating_fir_filter_ccf::sptr prefilter;

Expand All @@ -141,6 +147,8 @@ class p25_recorder : public gr::hier_block2, public Recorder
/* GR blocks */
gr::filter::fir_filter_ccf::sptr lpf;
gr::filter::fir_filter_fff::sptr sym_filter;
gr::filter::fft_filter_fff::sptr noise_filter;


gr::analog::sig_source_c::sptr lo;

Expand All @@ -152,11 +160,9 @@ class p25_recorder : public gr::hier_block2, public Recorder
gr::filter::pfb_arb_resampler_ccf::sptr arb_resampler;
gr::filter::rational_resampler_base_ccf::sptr downsample_sig;
gr::filter::rational_resampler_base_fff::sptr upsample_audio;
gr::analog::quadrature_demod_cf::sptr fm_demod;
gr::analog::feedforward_agc_cc::sptr agc;
gr::analog::agc2_ff::sptr demod_agc;
gr::analog::agc2_cc::sptr pre_demod_agc;
rx_agc_cc_sptr super_agc;
gr::analog::pll_freqdet_cf::sptr pll_freq_lock;

gr::blocks::nonstop_wavfile_sink::sptr wav_sink;

gr::blocks::short_to_float::sptr converter;
Expand All @@ -165,6 +171,7 @@ class p25_recorder : public gr::hier_block2, public Recorder
gr::blocks::multiply_const_ff::sptr multiplier;
gr::blocks::multiply_const_ff::sptr rescale;
gr::blocks::multiply_const_ff::sptr baseband_amp;
gr::blocks::multiply_const_ff::sptr pll_amp;
gr::blocks::complex_to_arg::sptr to_float;
gr::op25_repeater::fsk4_demod_ff::sptr fsk4_demod;
gr::op25_repeater::p25_frame_assembler::sptr op25_frame_assembler;
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