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307 lines
11 KiB
C++
307 lines
11 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2019 Edouard Griffiths, F4EXB //
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// Copyright (C) 2021 Jon Beniston, M7RCE //
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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 <complex.h>
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#include "dsp/dspengine.h"
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#include "dsp/dspengine.h"
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#include "util/db.h"
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#include "util/stepfunctions.h"
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#include "pipes/pipeendpoint.h"
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#include "maincore.h"
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#include "packetdemod.h"
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#include "packetdemodsink.h"
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PacketDemodSink::PacketDemodSink(PacketDemod *packetDemod) :
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m_packetDemod(packetDemod),
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m_channelSampleRate(PACKETDEMOD_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_f1(nullptr),
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m_f0(nullptr),
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m_corrBuf(nullptr),
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m_corrIdx(0),
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m_corrCnt(0)
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{
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m_magsq = 0.0;
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applySettings(m_settings, true);
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applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
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}
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PacketDemodSink::~PacketDemodSink()
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{
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}
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void PacketDemodSink::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 PacketDemodSink::processOneSample(Complex &ci)
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{
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Complex ca;
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// FM demodulation
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double magsqRaw;
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Real deviation;
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Real fmDemod = m_phaseDiscri.phaseDiscriminatorDelta(ci, magsqRaw, deviation);
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// Calculate average and peak levels for level meter
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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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m_corrBuf[m_corrIdx] = fmDemod;
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if (m_corrCnt >= m_correlationLength && magsq > 1e-7)
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{
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// Correlate with 1200 + 2200 baud complex exponentials
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Complex corrF0 = 0.0f;
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Complex corrF1 = 0.0f;
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for (int i = 0; i < m_correlationLength; i++)
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{
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int j = m_corrIdx - i;
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if (j < 0)
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j += m_correlationLength;
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corrF0 += m_f0[i] * m_corrBuf[j];
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corrF1 += m_f1[i] * m_corrBuf[j];
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}
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m_corrCnt--; // Avoid overflow in increment below
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// Low pass filter, to minimize changes above the baud rate
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Real f0Filt = m_lowpassF0.filter(std::abs(corrF0));
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Real f1Filt = m_lowpassF1.filter(std::abs(corrF1));
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// Determine which is the closest match and then quantise to 1 or -1
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// FIXME: We should try to account for the fact that higher frequencies can have preemphasis
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float diff = f1Filt - f0Filt;
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int sample = diff >= 0.0f ? 1 : 0;
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// Look for edge
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if (sample != m_samplePrev)
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{
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m_syncCount = PACKETDEMOD_CHANNEL_SAMPLE_RATE/m_settings.m_baud/2;
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}
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else
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{
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m_syncCount--;
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if (m_syncCount <= 0)
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{
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// HDLC deframing
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// Should be in the middle of the symbol
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// NRZI decoding
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int bit;
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if (sample != m_symbolPrev)
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bit = 0;
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else
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bit = 1;
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m_symbolPrev = sample;
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// Store in shift reg
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m_bits |= bit << m_bitCount;
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m_bitCount++;
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if (bit == 1)
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{
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m_onesCount++;
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// Shouldn't ever get 7 1s in a row
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if ((m_onesCount == 7) && m_gotSOP)
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{
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m_gotSOP = false;
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m_byteCount = 0;
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}
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}
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else if (bit == 0)
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{
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if (m_onesCount == 5)
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{
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// Remove bit-stuffing (5 1s followed by a 0)
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m_bitCount--;
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}
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else if (m_onesCount == 6)
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{
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// Start/end of packet
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if ((m_bitCount == 8) && (m_bits == 0x7e) && (m_byteCount > 0))
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{
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// End of packet
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// Check CRC is valid
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m_crc.init();
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m_crc.calculate(m_bytes, m_byteCount - 2);
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uint16_t calcCrc = m_crc.get();
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uint16_t rxCrc = m_bytes[m_byteCount-2] | (m_bytes[m_byteCount-1] << 8);
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if (calcCrc == rxCrc)
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{
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QByteArray rxPacket((char *)m_bytes, m_byteCount);
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qDebug() << "RX: " << rxPacket.toHex();
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if (getMessageQueueToChannel())
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{
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MainCore::MsgPacket *msg = MainCore::MsgPacket::create(m_packetDemod, rxPacket, QDateTime::currentDateTime()); // FIXME pointer
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getMessageQueueToChannel()->push(msg);
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}
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}
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else
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qDebug() << QString("CRC mismatch: %1 %2").arg(calcCrc, 4, 16, QLatin1Char('0')).arg(rxCrc, 4, 16, QLatin1Char('0'));
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// Reset state to start receiving next packet
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m_gotSOP = false;
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m_bits = 0;
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m_bitCount = 0;
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m_byteCount = 0;
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}
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else
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{
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// Start of packet
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m_gotSOP = true;
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m_bits = 0;
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m_bitCount = 0;
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m_byteCount = 0;
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}
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}
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m_onesCount = 0;
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}
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if (m_gotSOP)
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{
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if (m_bitCount == 8)
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{
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if (m_byteCount >= 512)
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{
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// Too many bytes
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m_gotSOP = false;
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m_byteCount = 0;
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}
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else
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{
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m_bytes[m_byteCount] = m_bits;
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m_byteCount++;
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}
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m_bits = 0;
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m_bitCount = 0;
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}
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}
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m_syncCount = PACKETDEMOD_CHANNEL_SAMPLE_RATE/m_settings.m_baud;
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}
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}
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m_samplePrev = sample;
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}
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m_corrIdx = (m_corrIdx + 1) % m_correlationLength;
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m_corrCnt++;
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}
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void PacketDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
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{
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qDebug() << "PacketDemodSink::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, PACKETDEMOD_CHANNEL_BANDWIDTH);
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m_interpolatorDistanceRemain = 0;
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m_interpolatorDistance = (Real) channelSampleRate / (Real) PACKETDEMOD_CHANNEL_SAMPLE_RATE;
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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 PacketDemodSink::applySettings(const PacketDemodSettings& settings, bool force)
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{
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qDebug() << "PacketDemodSink::applySettings:"
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<< " force: " << force;
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if (force)
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{
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m_lowpass.create(301, PACKETDEMOD_CHANNEL_SAMPLE_RATE, settings.m_rfBandwidth / 2.0f);
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m_phaseDiscri.setFMScaling(PACKETDEMOD_CHANNEL_SAMPLE_RATE / (2.0f * settings.m_fmDeviation));
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delete m_f1;
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delete m_f0;
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delete m_corrBuf;
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m_correlationLength = PACKETDEMOD_CHANNEL_SAMPLE_RATE/settings.m_baud;
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m_f1 = new Complex[m_correlationLength]();
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m_f0 = new Complex[m_correlationLength]();
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m_corrBuf = new Complex[m_correlationLength]();
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m_corrIdx = 0;
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m_corrCnt = 0;
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Real f0 = 0.0f;
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Real f1 = 0.0f;
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for (int i = 0; i < m_correlationLength; i++)
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{
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m_f0[i] = Complex(cos(f0), sin(f0));
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m_f1[i] = Complex(cos(f1), sin(f1));
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f0 += 2.0f*(Real)M_PI*2200.0f/PACKETDEMOD_CHANNEL_SAMPLE_RATE;
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f1 += 2.0f*(Real)M_PI*1200.0f/PACKETDEMOD_CHANNEL_SAMPLE_RATE;
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}
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m_lowpassF1.create(301, PACKETDEMOD_CHANNEL_SAMPLE_RATE, settings.m_baud * 1.1f);
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m_lowpassF0.create(301, PACKETDEMOD_CHANNEL_SAMPLE_RATE, settings.m_baud * 1.1f);
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m_samplePrev = 0;
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m_syncCount = 0;
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m_symbolPrev = 0;
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m_bits = 0;
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m_bitCount = 0;
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m_onesCount = 0;
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m_gotSOP = false;
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m_byteCount = 0;
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}
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m_settings = settings;
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}
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