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62 lines
2.6 KiB
C++
62 lines
2.6 KiB
C++
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///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2018 Edouard Griffiths, F4EXB //
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// //
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// Symbol synchronizer or symbol clock recovery mostly encapsulating //
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// liquid-dsp's symsync "object" //
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// //
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// This program is free software; you can redistribute it and/or modify //
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// it under the terms of the GNU General Public License as published by //
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// the Free Software Foundation as version 3 of the License, or //
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// //
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// This program is distributed in the hope that it will be useful, //
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// but WITHOUT ANY WARRANTY; without even the implied warranty of //
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
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// GNU General Public License V3 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 this program. If not, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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#include "symsync.h"
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SymbolSynchronizer::SymbolSynchronizer()
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{
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// For now use hardcoded values:
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// - RRC filter
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// - 4 samples per symbol
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// - 5 sybols delay filter
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// - 0.5 filter excess bandwidth factor
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// - 32 filter elements for the internal polyphase filter
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m_sync = symsync_crcf_create_rnyquist(LIQUID_FIRFILT_RRC, 4, 5, 0.5f, 32);
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// - 0.02 loop filter bandwidth factor
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symsync_crcf_set_lf_bw(m_sync, 0.02f);
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// - 4 samples per symbol output rate
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symsync_crcf_set_output_rate(m_sync, 4);
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m_syncSampleCount = 0;
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}
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SymbolSynchronizer::~SymbolSynchronizer()
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{
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symsync_crcf_destroy(m_sync);
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}
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Real SymbolSynchronizer::run(const Sample& s)
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{
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unsigned int nn;
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Real v = 0.0f;
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liquid_float_complex y = (s.m_real / SDR_RX_SCALEF) + (s.m_imag / SDR_RX_SCALEF)*I;
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symsync_crcf_execute(m_sync, &y, 1, m_z, &nn);
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for (unsigned int i = 0; i < nn; i++)
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{
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v = (m_syncSampleCount < 2) ? 1.0f : 0.0f; // actual sync is at 0
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if (m_syncSampleCount < 4) {
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m_syncSampleCount++;
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} else {
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m_syncSampleCount = 0;
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}
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}
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return v;
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}
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