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sdrangel/plugins/channelrx/demodnavtex/navtexdemodsink.cpp

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///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2023 Jon Beniston, M7RCE <jon@beniston.com> //
// Copyright (C) 2023 Daniele Forsi <iu5hkx@gmail.com> //
// //
// This program 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 as version 3 of the License, or //
// (at your option) any later version. //
// //
// This program 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 V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#include <QDebug>
#include <QRegularExpression>
#include <complex.h>
#include "dsp/dspengine.h"
#include "dsp/scopevis.h"
#include "util/db.h"
#include "maincore.h"
#include "navtexdemod.h"
#include "navtexdemodsink.h"
NavtexDemodSink::NavtexDemodSink(NavtexDemod *packetDemod) :
m_navtexDemod(packetDemod),
m_channelSampleRate(NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE),
m_channelFrequencyOffset(0),
m_magsqSum(0.0f),
m_magsqPeak(0.0f),
m_magsqCount(0),
m_messageQueueToChannel(nullptr),
m_exp(nullptr),
m_sampleBufferIndex(0)
{
m_magsq = 0.0;
m_sampleBuffer.resize(m_sampleBufferSize);
applySettings(m_settings, true);
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
m_lowpassComplex1.create(301, NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE, NavtexDemodSettings::NAVTEXDEMOD_BAUD_RATE * 1.1);
m_lowpassComplex2.create(301, NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE, NavtexDemodSettings::NAVTEXDEMOD_BAUD_RATE * 1.1);
}
NavtexDemodSink::~NavtexDemodSink()
{
delete[] m_exp;
}
void NavtexDemodSink::sampleToScope(Complex sample)
{
if (m_scopeSink)
{
Real r = std::real(sample) * SDR_RX_SCALEF;
Real i = std::imag(sample) * SDR_RX_SCALEF;
m_sampleBuffer[m_sampleBufferIndex++] = Sample(r, i);
if (m_sampleBufferIndex == m_sampleBufferSize)
{
std::vector<SampleVector::const_iterator> vbegin;
vbegin.push_back(m_sampleBuffer.begin());
m_scopeSink->feed(vbegin, m_sampleBufferSize);
m_sampleBufferIndex = 0;
}
}
}
void NavtexDemodSink::feed(const SampleVector::const_iterator& begin, const SampleVector::const_iterator& end)
{
Complex ci;
for (SampleVector::const_iterator it = begin; it != end; ++it)
{
Complex c(it->real(), it->imag());
c *= m_nco.nextIQ();
if (m_interpolatorDistance < 1.0f) // interpolate
{
while (!m_interpolator.interpolate(&m_interpolatorDistanceRemain, c, &ci))
{
processOneSample(ci);
m_interpolatorDistanceRemain += m_interpolatorDistance;
}
}
else // decimate
{
if (m_interpolator.decimate(&m_interpolatorDistanceRemain, c, &ci))
{
processOneSample(ci);
m_interpolatorDistanceRemain += m_interpolatorDistance;
}
}
}
}
void NavtexDemodSink::eraseChars(int n)
{
if (getMessageQueueToChannel())
{
QString msg = QString("%1").arg(QChar(0x8)); // Backspace
for (int i = 0; i < n; i++)
{
NavtexDemod::MsgCharacter *msg = NavtexDemod::MsgCharacter::create(QChar(0x8));
getMessageQueueToChannel()->push(msg);
}
}
}
void NavtexDemodSink::processOneSample(Complex &ci)
{
// Calculate average and peak levels for level meter
double magsqRaw = ci.real()*ci.real() + ci.imag()*ci.imag();;
Real magsq = magsqRaw / (SDR_RX_SCALED*SDR_RX_SCALED);
m_movingAverage(magsq);
m_magsq = m_movingAverage.asDouble();
m_magsqSum += magsq;
if (magsq > m_magsqPeak)
{
m_magsqPeak = magsq;
}
m_magsqCount++;
// Sum power while data is being received
if (m_gotSOP)
{
m_rssiMagSqSum += magsq;
m_rssiMagSqCount++;
}
ci /= SDR_RX_SCALEF;
// Correlate with expected frequencies
Complex exp = m_exp[m_expIdx];
m_expIdx = (m_expIdx + 1) % m_expLength;
Complex corr1 = ci * exp;
Complex corr2 = ci * std::conj(exp);
// Low pass filter
Real abs1Filt = std::abs(m_lowpassComplex1.filter(corr1));
Real abs2Filt = std::abs(m_lowpassComplex2.filter(corr2));
// Envelope calculation
m_movMax1(abs1Filt);
m_movMax2(abs2Filt);
Real env1 = m_movMax1.getMaximum();
Real env2 = m_movMax2.getMaximum();
// Automatic threshold correction to compensate for frequency selective fading
// http://www.w7ay.net/site/Technical/ATC/index.html
Real bias1 = abs1Filt - 0.5 * env1;
Real bias2 = abs2Filt - 0.5 * env2;
Real unbiasedData = abs1Filt - abs2Filt;
Real biasedData = bias1 - bias2;
// Save current data for edge detection
m_dataPrev = m_data;
// Set data according to stongest correlation
m_data = biasedData < 0;
// Generate sampling clock by aligning to correlator zero-crossing
if (m_data && !m_dataPrev)
{
if ((m_clockCount > 2) && (m_clockCount < m_samplesPerBit*3/4) && m_gotSOP)
{
//qDebug() << "Clock toggle ignored at " << m_clockCount;
}
else
{
m_clockCount = 0;
m_clock = false;
}
}
else
{
// Sample in middle of symbol
if (m_clockCount == m_samplesPerBit/2)
{
receiveBit(m_data);
m_clock = true;
}
m_clockCount = (m_clockCount + 1) % m_samplesPerBit;
if (m_clockCount == 0) {
m_clock = false;
}
}
// Select signals to feed to scope
Complex scopeSample;
switch (m_settings.m_scopeCh1)
{
case 0:
scopeSample.real(ci.real());
break;
case 1:
scopeSample.real(ci.imag());
break;
case 2:
scopeSample.real(real(exp));
break;
case 3:
scopeSample.real(imag(exp));
break;
case 4:
scopeSample.real(real(corr1));
break;
case 5:
scopeSample.real(imag(corr1));
break;
case 6:
scopeSample.real(real(corr2));
break;
case 7:
scopeSample.real(imag(corr2));
break;
case 8:
scopeSample.real(abs1Filt);
break;
case 9:
scopeSample.real(abs2Filt);
break;
case 10:
scopeSample.real(env1);
break;
case 11:
scopeSample.real(env2);
break;
case 12:
scopeSample.real(unbiasedData);
break;
case 13:
scopeSample.real(biasedData);
break;
case 14:
scopeSample.real(m_data);
break;
case 15:
scopeSample.real(m_clock);
break;
case 16:
scopeSample.real(m_bit);
break;
case 17:
scopeSample.real(m_gotSOP);
break;
}
switch (m_settings.m_scopeCh2)
{
case 0:
scopeSample.imag(ci.real());
break;
case 1:
scopeSample.imag(ci.imag());
break;
case 2:
scopeSample.imag(real(exp));
break;
case 3:
scopeSample.imag(imag(exp));
break;
case 4:
scopeSample.imag(real(corr1));
break;
case 5:
scopeSample.imag(imag(corr1));
break;
case 6:
scopeSample.imag(real(corr2));
break;
case 7:
scopeSample.imag(imag(corr2));
break;
case 8:
scopeSample.imag(abs1Filt);
break;
case 9:
scopeSample.imag(abs2Filt);
break;
case 10:
scopeSample.imag(env1);
break;
case 11:
scopeSample.imag(env2);
break;
case 12:
scopeSample.imag(unbiasedData);
break;
case 13:
scopeSample.imag(biasedData);
break;
case 14:
scopeSample.imag(m_data);
break;
case 15:
scopeSample.imag(m_clock);
break;
case 16:
scopeSample.imag(m_bit);
break;
case 17:
scopeSample.imag(m_gotSOP);
break;
}
sampleToScope(scopeSample);
}
void NavtexDemodSink::receiveBit(bool bit)
{
m_bit = bit;
// Store in shift reg
m_bits = (m_bits << 1) | m_bit;
m_bitCount++;
if (!m_gotSOP)
{
if (m_bitCount == 14)
{
if ((m_bits & 0x3fff) == 0x19f8) // phase 2 followed by phase 1
{
m_gotSOP = true;
m_bitCount = 0;
m_sitorBDecoder.init();
m_rssiMagSqSum = 0.0;
m_rssiMagSqCount = 0;
}
else
{
m_bitCount--;
}
}
}
else
{
if (m_bitCount == 7)
{
signed char c = m_sitorBDecoder.decode(m_bits & 0x7f);
if (c != -1)
{
//qDebug() << "Out: " << SitorBDecoder::printable(c);
m_consecutiveErrors = 0;
if ((c != '<') && (c != '>') && (c != 0x2))
{
// 7 bytes per second, so may as well send individually to be displayed
if (getMessageQueueToChannel())
{
NavtexDemod::MsgCharacter *msg = NavtexDemod::MsgCharacter::create(SitorBDecoder::printable(c));
getMessageQueueToChannel()->push(msg);
}
// Add character to message buffer
m_messageBuffer.append(QChar(c));
}
else
{
if (m_messageBuffer.size() > 0)
{
QRegularExpression re("[Z*][C*][Z*][C*](.|\n|\r)*[N*][N*][N*][N*]");
QRegularExpressionMatch match = re.match(m_messageBuffer);
if (match.hasMatch())
{
if (getMessageQueueToChannel())
{
NavtexMessage navtexMsg = NavtexMessage(match.captured(0));
float rssi = CalcDb::dbPower(m_rssiMagSqSum / m_rssiMagSqCount);
NavtexDemod::MsgMessage *msg = NavtexDemod::MsgMessage::create(navtexMsg, m_sitorBDecoder.getErrors(), rssi);
getMessageQueueToChannel()->push(msg);
}
// Navtex messages can span multiple blocks?
m_messageBuffer = "";
}
}
if (c == 0x2) // End of text
{
// Reset demod
init();
}
}
}
if (c == '*')
{
m_errorCount++;
m_consecutiveErrors++;
// ITU 476-5 just says return to standby after the percentage of
// mutilated signals received has reached a predetermined value
// without saying what that value is
if (m_messageBuffer.size() >= 12)
{
float errorPC = m_errorCount / (float)(m_messageBuffer.size() + m_errorCount);
if (errorPC >= 0.2f)
{
//qDebug() << "Too many errors" << m_errorCount << m_messageBuffer.size();
init();
}
}
else if (m_errorCount >= 3)
{
//qDebug() << "Too many errors" << m_errorCount << m_messageBuffer.size();
eraseChars(m_messageBuffer.size());
init();
}
if (m_consecutiveErrors >= 5)
{
//qDebug() << "Too many consecutive errors";
init();
}
}
m_bitCount = 0;
}
}
}
void NavtexDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
{
qDebug() << "NavtexDemodSink::applyChannelSettings:"
<< " channelSampleRate: " << channelSampleRate
<< " channelFrequencyOffset: " << channelFrequencyOffset;
if ((m_channelFrequencyOffset != channelFrequencyOffset) ||
(m_channelSampleRate != channelSampleRate) || force)
{
m_nco.setFreq(-channelFrequencyOffset, channelSampleRate);
}
if ((m_channelSampleRate != channelSampleRate) || force)
{
m_interpolator.create(16, channelSampleRate, m_settings.m_rfBandwidth / 2.2);
m_interpolatorDistance = (Real) channelSampleRate / (Real) NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE;
m_interpolatorDistanceRemain = m_interpolatorDistance;
}
m_channelSampleRate = channelSampleRate;
m_channelFrequencyOffset = channelFrequencyOffset;
}
void NavtexDemodSink::init()
{
m_expIdx = 0;
m_bit = 0;
m_bits = 0;
m_bitCount = 0;
m_gotSOP = false;
m_errorCount = 0;
m_clockCount = 0;
m_clock = 0;
m_rssiMagSqSum = 0.0;
m_rssiMagSqCount = 0;
m_consecutiveErrors = 0;
m_sitorBDecoder.init();
m_messageBuffer = "";
}
void NavtexDemodSink::applySettings(const NavtexDemodSettings& settings, bool force)
{
qDebug() << "NavtexDemodSink::applySettings:"
<< " m_rfBandwidth: " << settings.m_rfBandwidth
<< " force: " << force;
if ((settings.m_rfBandwidth != m_settings.m_rfBandwidth) || force)
{
m_interpolator.create(16, m_channelSampleRate, settings.m_rfBandwidth / 2.2);
m_interpolatorDistance = (Real) m_channelSampleRate / (Real) NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE;
m_interpolatorDistanceRemain = m_interpolatorDistance;
}
if (force)
{
delete[] m_exp;
m_exp = new Complex[m_expLength];
Real f0 = 0.0f;
for (int i = 0; i < m_expLength; i++)
{
m_exp[i] = Complex(cos(f0), sin(f0));
f0 += 2.0f * (Real)M_PI * (NavtexDemodSettings::NAVTEXDEMOD_FREQUENCY_SHIFT/2.0f) / NavtexDemodSettings::NAVTEXDEMOD_CHANNEL_SAMPLE_RATE;
}
init();
// Due to start and stop bits, we should get mark and space at least every 8 bits
// while something is being transmitted
m_movMax1.setSize(m_samplesPerBit * 8);
m_movMax2.setSize(m_samplesPerBit * 8);
}
m_settings = settings;
}
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