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sdrangel/plugins/channelrx/demodpacket/packetdemodsink.cpp

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///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2021, 2023 Jon Beniston, M7RCE <jon@beniston.com> //
// Copyright (C) 2021-2022 Edouard Griffiths, F4EXB <f4exb06@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 <complex.h>
#include "dsp/dspengine.h"
#include "dsp/datafifo.h"
#include "util/db.h"
#include "util/stepfunctions.h"
#include "maincore.h"
#include "packetdemod.h"
#include "packetdemodsink.h"
PacketDemodSink::PacketDemodSink(PacketDemod *packetDemod) :
m_packetDemod(packetDemod),
m_channelSampleRate(PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE),
m_channelFrequencyOffset(0),
m_magsqSum(0.0f),
m_magsqPeak(0.0f),
m_magsqCount(0),
m_messageQueueToChannel(nullptr),
m_f1(nullptr),
m_f0(nullptr),
m_corrBuf(nullptr),
m_corrIdx(0),
m_corrCnt(0)
{
m_magsq = 0.0;
m_demodBuffer.resize(1<<12);
m_demodBufferFill = 0;
applySettings(m_settings, true);
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
}
PacketDemodSink::~PacketDemodSink()
{
delete[] m_f1;
delete[] m_f0;
delete[] m_corrBuf;
}
void PacketDemodSink::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 PacketDemodSink::processOneSample(Complex &ci)
{
Complex ca;
// FM demodulation
double magsqRaw;
Real deviation;
Real fmDemod = m_phaseDiscri.phaseDiscriminatorDelta(ci, magsqRaw, deviation);
// Calculate average and peak levels for level meter
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++;
m_corrBuf[m_corrIdx] = fmDemod;
if (m_corrCnt >= m_correlationLength)
{
// Correlate with 1200 + 2200 baud complex exponentials
Complex corrF0 = 0.0f;
Complex corrF1 = 0.0f;
for (int i = 0; i < m_correlationLength; i++)
{
int j = m_corrIdx - i;
if (j < 0)
j += m_correlationLength;
corrF0 += m_f0[i] * m_corrBuf[j];
corrF1 += m_f1[i] * m_corrBuf[j];
}
m_corrCnt--; // Avoid overflow in increment below
// Low pass filter, to minimize changes above the baud rate
Real f0Filt = m_lowpassF0.filter(std::abs(corrF0));
Real f1Filt = m_lowpassF1.filter(std::abs(corrF1));
// Determine which is the closest match and then quantise to 1 or -1
// FIXME: We should try to account for the fact that higher frequencies can have preemphasis
float diff = f1Filt - f0Filt;
int sample = diff >= 0.0f ? 1 : 0;
// Look for edge
if (sample != m_samplePrev)
{
m_syncCount = PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE/m_settings.getBaudRate()/2;
}
else
{
m_syncCount--;
if (m_syncCount <= 0)
{
// HDLC deframing
// Should be in the middle of the symbol
// NRZI decoding
int bit;
if (sample != m_symbolPrev)
bit = 0;
else
bit = 1;
m_symbolPrev = sample;
// Store in shift reg
m_bits |= bit << m_bitCount;
m_bitCount++;
if (bit == 1)
{
m_onesCount++;
// Shouldn't ever get 7 1s in a row
if ((m_onesCount == 7) && m_gotSOP)
{
m_gotSOP = false;
m_byteCount = 0;
}
}
else if (bit == 0)
{
if (m_onesCount == 5)
{
// Remove bit-stuffing (5 1s followed by a 0)
m_bitCount--;
}
else if (m_onesCount == 6)
{
// Start/end of packet
if ((m_bitCount == 8) && (m_bits == 0x7e) && (m_byteCount > 0))
{
// End of packet
// Check CRC is valid
m_crc.init();
m_crc.calculate(m_bytes, m_byteCount - 2);
uint16_t calcCrc = m_crc.get();
uint16_t rxCrc = m_bytes[m_byteCount-2] | (m_bytes[m_byteCount-1] << 8);
if (calcCrc == rxCrc)
{
QByteArray rxPacket((char *)m_bytes, m_byteCount);
qDebug() << "RX: " << rxPacket.toHex();
if (getMessageQueueToChannel())
{
MainCore::MsgPacket *msg = MainCore::MsgPacket::create(m_packetDemod, rxPacket, QDateTime::currentDateTime()); // FIXME pointer
getMessageQueueToChannel()->push(msg);
}
}
else
qDebug() << QString("PacketDemodSink::processOneSample: CRC mismatch: %1 %2")
.arg(calcCrc, 4, 16, QLatin1Char('0'))
.arg(rxCrc, 4, 16, QLatin1Char('0'));
// Reset state to start receiving next packet
m_gotSOP = false;
m_bits = 0;
m_bitCount = 0;
m_byteCount = 0;
}
else
{
// Start of packet
m_gotSOP = true;
m_bits = 0;
m_bitCount = 0;
m_byteCount = 0;
}
}
m_onesCount = 0;
}
if (m_gotSOP)
{
if (m_bitCount == 8)
{
if (m_byteCount >= 512)
{
// Too many bytes
m_gotSOP = false;
m_byteCount = 0;
}
else
{
m_bytes[m_byteCount] = m_bits;
m_byteCount++;
}
m_bits = 0;
m_bitCount = 0;
}
}
m_syncCount = PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE/m_settings.getBaudRate();
}
}
m_samplePrev = sample;
}
m_corrIdx = (m_corrIdx + 1) % m_correlationLength;
m_corrCnt++;
m_demodBuffer[m_demodBufferFill++] = fmDemod * std::numeric_limits<int16_t>::max();
if (m_demodBufferFill >= m_demodBuffer.size())
{
QList<ObjectPipe*> dataPipes;
MainCore::instance()->getDataPipes().getDataPipes(m_channel, "demod", dataPipes);
if (dataPipes.size() > 0)
{
QList<ObjectPipe*>::iterator it = dataPipes.begin();
for (; it != dataPipes.end(); ++it)
{
DataFifo *fifo = qobject_cast<DataFifo*>((*it)->m_element);
if (fifo) {
fifo->write((quint8*) &m_demodBuffer[0], m_demodBuffer.size() * sizeof(qint16), DataFifo::DataTypeI16);
}
}
}
m_demodBufferFill = 0;
}
}
void PacketDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
{
qDebug() << "PacketDemodSink::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) PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE;
m_interpolatorDistanceRemain = m_interpolatorDistance;
}
m_channelSampleRate = channelSampleRate;
m_channelFrequencyOffset = channelFrequencyOffset;
}
void PacketDemodSink::applySettings(const PacketDemodSettings& settings, bool force)
{
qDebug() << "PacketDemodSink::applySettings:"
<< " 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) PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE;
m_interpolatorDistanceRemain = m_interpolatorDistance;
}
if ((settings.m_fmDeviation != m_settings.m_fmDeviation) || force)
{
m_phaseDiscri.setFMScaling(PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE / (2.0f * settings.m_fmDeviation));
}
if (force)
{
delete[] m_f1;
delete[] m_f0;
delete[] m_corrBuf;
m_correlationLength = PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE/settings.getBaudRate();
m_f1 = new Complex[m_correlationLength]();
m_f0 = new Complex[m_correlationLength]();
m_corrBuf = new Complex[m_correlationLength]();
m_corrIdx = 0;
m_corrCnt = 0;
Real f0 = 0.0f;
Real f1 = 0.0f;
for (int i = 0; i < m_correlationLength; i++)
{
m_f0[i] = Complex(cos(f0), sin(f0));
m_f1[i] = Complex(cos(f1), sin(f1));
f0 += 2.0f*(Real)M_PI*2200.0f/PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE;
f1 += 2.0f*(Real)M_PI*1200.0f/PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE;
}
m_lowpassF1.create(301, PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE, settings.getBaudRate() * 1.1f);
m_lowpassF0.create(301, PacketDemodSettings::PACKETDEMOD_CHANNEL_SAMPLE_RATE, settings.getBaudRate() * 1.1f);
m_samplePrev = 0;
m_syncCount = 0;
m_symbolPrev = 0;
m_bits = 0;
m_bitCount = 0;
m_onesCount = 0;
m_gotSOP = false;
m_byteCount = 0;
}
m_settings = settings;
}
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