mirror of
https://github.com/f4exb/sdrangel.git
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494 lines
15 KiB
C++
494 lines
15 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2023 Jon Beniston, M7RCE <jon@beniston.com> //
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// Copyright (C) 2023 Daniele Forsi <iu5hkx@gmail.com> //
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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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// (at your option) any later version. //
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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 <QDebug>
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#include <QRegularExpression>
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#include <complex.h>
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#include "dsp/scopevis.h"
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#include "util/db.h"
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#include "navtexdemod.h"
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#include "navtexdemodsink.h"
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NavtexDemodSink::NavtexDemodSink(NavtexDemod *packetDemod) :
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m_navtexDemod(packetDemod),
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m_channelSampleRate(NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE),
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m_channelFrequencyOffset(0),
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m_magsqSum(0.0f),
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m_magsqPeak(0.0f),
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m_magsqCount(0),
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m_messageQueueToChannel(nullptr),
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m_exp(nullptr),
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m_sampleBufferIndex(0)
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{
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m_magsq = 0.0;
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m_sampleBuffer.resize(m_sampleBufferSize);
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applySettings(m_settings, true);
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applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
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m_lowpassComplex1.create(301, NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE, NavtexDemodSettings::NAVTEXDEMOD_BAUD_RATE * 1.1);
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m_lowpassComplex2.create(301, NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE, NavtexDemodSettings::NAVTEXDEMOD_BAUD_RATE * 1.1);
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}
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NavtexDemodSink::~NavtexDemodSink()
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{
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delete[] m_exp;
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}
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void NavtexDemodSink::sampleToScope(Complex sample)
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{
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if (m_scopeSink)
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{
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Real r = std::real(sample) * SDR_RX_SCALEF;
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Real i = std::imag(sample) * SDR_RX_SCALEF;
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m_sampleBuffer[m_sampleBufferIndex++] = Sample(r, i);
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if (m_sampleBufferIndex == m_sampleBufferSize)
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{
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std::vector<SampleVector::const_iterator> vbegin;
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vbegin.push_back(m_sampleBuffer.begin());
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m_scopeSink->feed(vbegin, m_sampleBufferSize);
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m_sampleBufferIndex = 0;
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}
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}
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}
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void NavtexDemodSink::feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end)
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{
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Complex ci;
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for (SampleVector::const_iterator it = begin; it != end; ++it)
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{
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Complex c(it->real(), it->imag());
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c *= m_nco.nextIQ();
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if (m_interpolatorDistance < 1.0f) // interpolate
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{
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while (!m_interpolator.interpolate(&m_interpolatorDistanceRemain, c, &ci))
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{
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processOneSample(ci);
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m_interpolatorDistanceRemain += m_interpolatorDistance;
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}
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}
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else // decimate
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{
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if (m_interpolator.decimate(&m_interpolatorDistanceRemain, c, &ci))
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{
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processOneSample(ci);
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m_interpolatorDistanceRemain += m_interpolatorDistance;
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}
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}
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}
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}
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void NavtexDemodSink::eraseChars(int n)
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{
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if (getMessageQueueToChannel())
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{
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QString msg = QString("%1").arg(QChar(0x8)); // Backspace
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for (int i = 0; i < n; i++)
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{
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NavtexDemod::MsgCharacter *msg = NavtexDemod::MsgCharacter::create(QChar(0x8));
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getMessageQueueToChannel()->push(msg);
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}
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}
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}
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void NavtexDemodSink::processOneSample(Complex &ci)
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{
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// Calculate average and peak levels for level meter
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double magsqRaw = ci.real()*ci.real() + ci.imag()*ci.imag();;
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Real magsq = magsqRaw / (SDR_RX_SCALED*SDR_RX_SCALED);
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m_movingAverage(magsq);
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m_magsq = m_movingAverage.asDouble();
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m_magsqSum += magsq;
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if (magsq > m_magsqPeak)
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{
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m_magsqPeak = magsq;
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}
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m_magsqCount++;
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// Sum power while data is being received
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if (m_gotSOP)
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{
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m_rssiMagSqSum += magsq;
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m_rssiMagSqCount++;
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}
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ci /= SDR_RX_SCALEF;
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// Correlate with expected frequencies
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Complex exp = m_exp[m_expIdx];
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m_expIdx = (m_expIdx + 1) % m_expLength;
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Complex corr1 = ci * exp;
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Complex corr2 = ci * std::conj(exp);
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// Low pass filter
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Real abs1Filt = std::abs(m_lowpassComplex1.filter(corr1));
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Real abs2Filt = std::abs(m_lowpassComplex2.filter(corr2));
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// Envelope calculation
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m_movMax1(abs1Filt);
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m_movMax2(abs2Filt);
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Real env1 = m_movMax1.getMaximum();
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Real env2 = m_movMax2.getMaximum();
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// Automatic threshold correction to compensate for frequency selective fading
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// http://www.w7ay.net/site/Technical/ATC/index.html
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Real bias1 = abs1Filt - 0.5 * env1;
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Real bias2 = abs2Filt - 0.5 * env2;
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Real unbiasedData = abs1Filt - abs2Filt;
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Real biasedData = bias1 - bias2;
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// Save current data for edge detection
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m_dataPrev = m_data;
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// Set data according to strongest correlation
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m_data = biasedData < 0;
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// Generate sampling clock by aligning to correlator zero-crossing
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if (m_data && !m_dataPrev)
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{
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if ((m_clockCount > 2) && (m_clockCount < m_samplesPerBit*3/4) && m_gotSOP)
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{
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//qDebug() << "Clock toggle ignored at " << m_clockCount;
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}
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else
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{
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m_clockCount = 0;
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m_clock = false;
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}
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}
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else
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{
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// Sample in middle of symbol
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if (m_clockCount == m_samplesPerBit/2)
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{
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receiveBit(m_data);
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m_clock = true;
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}
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m_clockCount = (m_clockCount + 1) % m_samplesPerBit;
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if (m_clockCount == 0) {
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m_clock = false;
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}
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}
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// Select signals to feed to scope
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Complex scopeSample;
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switch (m_settings.m_scopeCh1)
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{
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case 0:
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scopeSample.real(ci.real());
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break;
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case 1:
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scopeSample.real(ci.imag());
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break;
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case 2:
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scopeSample.real(real(exp));
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break;
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case 3:
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scopeSample.real(imag(exp));
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break;
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case 4:
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scopeSample.real(real(corr1));
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break;
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case 5:
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scopeSample.real(imag(corr1));
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break;
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case 6:
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scopeSample.real(real(corr2));
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break;
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case 7:
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scopeSample.real(imag(corr2));
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break;
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case 8:
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scopeSample.real(abs1Filt);
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break;
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case 9:
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scopeSample.real(abs2Filt);
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break;
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case 10:
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scopeSample.real(env1);
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break;
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case 11:
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scopeSample.real(env2);
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break;
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case 12:
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scopeSample.real(unbiasedData);
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break;
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case 13:
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scopeSample.real(biasedData);
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break;
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case 14:
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scopeSample.real(m_data);
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break;
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case 15:
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scopeSample.real(m_clock);
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break;
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case 16:
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scopeSample.real(m_bit);
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break;
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case 17:
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scopeSample.real(m_gotSOP);
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break;
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}
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switch (m_settings.m_scopeCh2)
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{
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case 0:
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scopeSample.imag(ci.real());
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break;
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case 1:
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scopeSample.imag(ci.imag());
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break;
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case 2:
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scopeSample.imag(real(exp));
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break;
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case 3:
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scopeSample.imag(imag(exp));
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break;
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case 4:
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scopeSample.imag(real(corr1));
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break;
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case 5:
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scopeSample.imag(imag(corr1));
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break;
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case 6:
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scopeSample.imag(real(corr2));
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break;
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case 7:
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scopeSample.imag(imag(corr2));
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break;
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case 8:
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scopeSample.imag(abs1Filt);
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break;
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case 9:
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scopeSample.imag(abs2Filt);
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break;
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case 10:
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scopeSample.imag(env1);
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break;
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case 11:
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scopeSample.imag(env2);
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break;
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case 12:
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scopeSample.imag(unbiasedData);
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break;
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case 13:
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scopeSample.imag(biasedData);
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break;
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case 14:
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scopeSample.imag(m_data);
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break;
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case 15:
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scopeSample.imag(m_clock);
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break;
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case 16:
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scopeSample.imag(m_bit);
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break;
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case 17:
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scopeSample.imag(m_gotSOP);
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break;
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}
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sampleToScope(scopeSample);
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}
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void NavtexDemodSink::receiveBit(bool bit)
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{
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m_bit = bit;
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// Store in shift reg
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m_bits = (m_bits << 1) | m_bit;
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m_bitCount++;
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if (!m_gotSOP)
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{
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if (m_bitCount == 14)
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{
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if ((m_bits & 0x3fff) == 0x19f8) // phase 2 followed by phase 1
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{
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m_gotSOP = true;
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m_bitCount = 0;
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m_sitorBDecoder.init();
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m_rssiMagSqSum = 0.0;
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m_rssiMagSqCount = 0;
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}
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else
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{
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m_bitCount--;
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}
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}
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}
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else
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{
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if (m_bitCount == 7)
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{
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signed char c = m_sitorBDecoder.decode(m_bits & 0x7f);
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if (c != -1)
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{
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//qDebug() << "Out: " << SitorBDecoder::printable(c);
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m_consecutiveErrors = 0;
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if ((c != '<') && (c != '>') && (c != 0x2))
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{
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// 7 bytes per second, so may as well send individually to be displayed
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if (getMessageQueueToChannel())
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{
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NavtexDemod::MsgCharacter *msg = NavtexDemod::MsgCharacter::create(SitorBDecoder::printable(c));
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getMessageQueueToChannel()->push(msg);
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}
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// Add character to message buffer
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m_messageBuffer.append(QChar(c));
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}
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else
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{
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if (m_messageBuffer.size() > 0)
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{
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QRegularExpression re("[Z*][C*][Z*][C*](.|\n|\r)*[N*][N*][N*][N*]");
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QRegularExpressionMatch match = re.match(m_messageBuffer);
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if (match.hasMatch())
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{
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if (getMessageQueueToChannel())
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{
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NavtexMessage navtexMsg = NavtexMessage(match.captured(0));
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float rssi = CalcDb::dbPower(m_rssiMagSqSum / m_rssiMagSqCount);
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NavtexDemod::MsgMessage *msg = NavtexDemod::MsgMessage::create(navtexMsg, m_sitorBDecoder.getErrors(), rssi);
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getMessageQueueToChannel()->push(msg);
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}
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// Navtex messages can span multiple blocks?
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m_messageBuffer = "";
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}
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}
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if (c == 0x2) // End of text
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{
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// Reset demod
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init();
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}
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}
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}
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if (c == '*')
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{
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m_errorCount++;
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m_consecutiveErrors++;
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// ITU 476-5 just says return to standby after the percentage of
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// mutilated signals received has reached a predetermined value
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// without saying what that value is
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if (m_messageBuffer.size() >= 12)
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{
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float errorPC = m_errorCount / (float)(m_messageBuffer.size() + m_errorCount);
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if (errorPC >= 0.2f)
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{
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//qDebug() << "Too many errors" << m_errorCount << m_messageBuffer.size();
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init();
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}
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}
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else if (m_errorCount >= 3)
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{
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//qDebug() << "Too many errors" << m_errorCount << m_messageBuffer.size();
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eraseChars(m_messageBuffer.size());
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init();
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}
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if (m_consecutiveErrors >= 5)
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{
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//qDebug() << "Too many consecutive errors";
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init();
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}
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}
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m_bitCount = 0;
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}
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}
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}
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void NavtexDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
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{
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qDebug() << "NavtexDemodSink::applyChannelSettings:"
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<< " channelSampleRate: " << channelSampleRate
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<< " channelFrequencyOffset: " << channelFrequencyOffset;
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if ((m_channelFrequencyOffset != channelFrequencyOffset) ||
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(m_channelSampleRate != channelSampleRate) || force)
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{
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m_nco.setFreq(-channelFrequencyOffset, channelSampleRate);
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}
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if ((m_channelSampleRate != channelSampleRate) || force)
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{
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m_interpolator.create(16, channelSampleRate, m_settings.m_rfBandwidth / 2.2);
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m_interpolatorDistance = (Real) channelSampleRate / (Real) NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE;
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m_interpolatorDistanceRemain = m_interpolatorDistance;
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}
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m_channelSampleRate = channelSampleRate;
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m_channelFrequencyOffset = channelFrequencyOffset;
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}
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void NavtexDemodSink::init()
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{
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m_expIdx = 0;
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m_bit = 0;
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m_bits = 0;
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m_bitCount = 0;
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m_gotSOP = false;
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m_errorCount = 0;
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m_clockCount = 0;
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m_clock = 0;
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m_rssiMagSqSum = 0.0;
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m_rssiMagSqCount = 0;
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m_consecutiveErrors = 0;
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m_sitorBDecoder.init();
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m_messageBuffer = "";
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}
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void NavtexDemodSink::applySettings(const NavtexDemodSettings& settings, bool force)
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{
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qDebug() << "NavtexDemodSink::applySettings:"
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<< " m_rfBandwidth: " << settings.m_rfBandwidth
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<< " force: " << force;
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if ((settings.m_rfBandwidth != m_settings.m_rfBandwidth) || force)
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{
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m_interpolator.create(16, m_channelSampleRate, settings.m_rfBandwidth / 2.2);
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m_interpolatorDistance = (Real) m_channelSampleRate / (Real) NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE;
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m_interpolatorDistanceRemain = m_interpolatorDistance;
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}
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if (force)
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{
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delete[] m_exp;
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m_exp = new Complex[m_expLength];
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Real f0 = 0.0f;
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for (int i = 0; i < m_expLength; i++)
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{
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m_exp[i] = Complex(cos(f0), sin(f0));
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f0 += 2.0f * (Real)M_PI * (NavtexDemodSettings::NAVTEXDEMOD_FREQUENCY_SHIFT/2.0f) / NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE;
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}
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init();
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// Due to start and stop bits, we should get mark and space at least every 8 bits
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// while something is being transmitted
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m_movMax1.setSize(m_samplesPerBit * 8);
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m_movMax2.setSize(m_samplesPerBit * 8);
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}
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m_settings = settings;
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}
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