mirror of
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572 lines
20 KiB
C++
572 lines
20 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/datafifo.h"
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#include "dsp/scopevis.h"
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#include "util/db.h"
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#include "util/stepfunctions.h"
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#include "util/reedsolomon.h"
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#include "maincore.h"
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#include "radiosondedemod.h"
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#include "radiosondedemodsink.h"
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const uint8_t RadiosondeDemodSink::m_descramble[64] = {
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0x96, 0x83, 0x3E, 0x51, 0xB1, 0x49, 0x08, 0x98,
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0x32, 0x05, 0x59, 0x0E, 0xF9, 0x44, 0xC6, 0x26,
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0x21, 0x60, 0xC2, 0xEA, 0x79, 0x5D, 0x6D, 0xA1,
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0x54, 0x69, 0x47, 0x0C, 0xDC, 0xE8, 0x5C, 0xF1,
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0xF7, 0x76, 0x82, 0x7F, 0x07, 0x99, 0xA2, 0x2C,
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0x93, 0x7C, 0x30, 0x63, 0xF5, 0x10, 0x2E, 0x61,
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0xD0, 0xBC, 0xB4, 0xB6, 0x06, 0xAA, 0xF4, 0x23,
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0x78, 0x6E, 0x3B, 0xAE, 0xBF, 0x7B, 0x4C, 0xC1
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};
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RadiosondeDemodSink::RadiosondeDemodSink(RadiosondeDemod *radiosondeDemod) :
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m_scopeSink(nullptr),
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m_radiosondeDemod(radiosondeDemod),
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m_channelSampleRate(RadiosondeDemodSettings::RADIOSONDEDEMOD_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_rxBuf(nullptr),
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m_train(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_demodBuffer.resize(1<<12);
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m_demodBufferFill = 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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}
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RadiosondeDemodSink::~RadiosondeDemodSink()
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{
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delete[] m_rxBuf;
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delete[] m_train;
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}
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void RadiosondeDemodSink::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 RadiosondeDemodSink::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 RadiosondeDemodSink::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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// Gaussian filter
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Real filt = m_pulseShape.filter(fmDemod);
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// An input frequency offset corresponds to a DC offset after FM demodulation
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// What frequency offset is RS41 specified too?
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// We need to remove this, otherwise it may effect the sampling
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// To calculate what it is, we sum the training sequence, which should be zero
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// Clip, as large noise can result in high correlation
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// Don't clip to 1.0 - as there may be some DC offset (1k/4.8k max dev=0.2)
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Real filtClipped;
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filtClipped = std::fmax(-1.4, std::fmin(1.4, filt));
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// Buffer filtered samples. We buffer enough samples for a max length message
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// before trying to demod, so false triggering can't make us miss anything
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m_rxBuf[m_rxBufIdx] = filtClipped;
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m_rxBufIdx = (m_rxBufIdx + 1) % m_rxBufLength;
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m_rxBufCnt = std::min(m_rxBufCnt + 1, m_rxBufLength);
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Real corr = 0.0f;
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bool scopeCRCValid = false;
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bool scopeCRCInvalid = false;
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Real dcOffset = 0.0f;
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bool thresholdMet = false;
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bool gotSOP = false;
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if ((m_rxBufCnt >= m_rxBufLength))
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{
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// Correlate with training sequence
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corr = correlate(m_rxBufIdx);
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// If we meet threshold, try to demod
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// Take abs value, to account for both initial phases
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thresholdMet = fabs(corr) >= m_settings.m_correlationThreshold;
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if (thresholdMet)
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{
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// Try to see if starting at a later sample improves correlation
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int maxCorrOffset = 0;
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Real maxCorr;
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do
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{
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maxCorr = fabs(corr);
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maxCorrOffset++;
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corr = correlate(m_rxBufIdx + maxCorrOffset);
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}
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while (fabs(corr) > maxCorr);
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maxCorrOffset--;
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// Calculate mean of preamble as DC offset (as it should be 0 on an ideal signal)
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Real trainingSum = 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_rxBufIdx + maxCorrOffset + i) % m_rxBufLength;
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trainingSum += m_rxBuf[j];
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}
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dcOffset = trainingSum/m_correlationLength;
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// Start demod after (most of) preamble
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int x = (m_rxBufIdx + maxCorrOffset + m_correlationLength*3/4 + 0) % m_rxBufLength;
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// Attempt to demodulate
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uint64_t bits = 0;
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int bitCount = 0;
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int byteCount = 0;
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QList<int> sampleIdxs;
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for (int sampleIdx = 0; sampleIdx < m_rxBufLength; sampleIdx += m_samplesPerSymbol)
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{
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// Sum and slice
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// Summing 3 samples seems to give a very small improvement vs just using 1
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int sampleCnt = 3;
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int sampleOffset = -1;
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Real sampleSum = 0.0f;
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for (int i = 0; i < sampleCnt; i++) {
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sampleSum += m_rxBuf[(x + sampleOffset + i) % m_rxBufLength] - dcOffset;
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sampleIdxs.append((x + sampleOffset + i) % m_rxBufLength);
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}
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int symbol = sampleSum >= 0.0f ? 1 : 0;
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// Move to next symbol
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x = (x + m_samplesPerSymbol) % m_rxBufLength;
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// Symbols map directly to bits
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int bit = symbol;
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// Store in shift reg (little endian)
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bits |= ((uint64_t)bit) << bitCount;
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bitCount++;
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if (gotSOP)
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{
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if (bitCount == 8)
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{
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// Got a complete byte
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m_bytes[byteCount] = bits;
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byteCount++;
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bits = 0;
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bitCount = 0;
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if (byteCount >= RS41_LENGTH_STD)
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{
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// Get expected length of frame
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uint8_t frameType = m_bytes[RS41_OFFSET_FRAME_TYPE] ^ m_descramble[RS41_OFFSET_FRAME_TYPE];
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int length = RS41Frame::getFrameLength(frameType);
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// Have we received a complete frame?
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if (byteCount == length)
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{
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bool ok = processFrame(length, corr, sampleIdx);
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scopeCRCValid = ok;
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scopeCRCInvalid = !ok;
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break;
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}
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}
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}
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}
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else if (bits == 0xf812962211cab610ULL) // Scrambled header
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{
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// Start of packet
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gotSOP = true;
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bits = 0;
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bitCount = 0;
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m_bytes[0] = 0x10;
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m_bytes[1] = 0xb6;
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m_bytes[2] = 0xca;
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m_bytes[3] = 0x11;
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m_bytes[4] = 0x22;
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m_bytes[5] = 0x96;
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m_bytes[6] = 0x12;
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m_bytes[7] = 0xf8;
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byteCount = 8;
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}
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else
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{
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if (bitCount == 64)
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{
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bits >>= 1;
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bitCount--;
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}
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if (sampleIdx >= 16 * 8 * m_samplesPerSymbol)
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{
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// Too many bits without receving header
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break;
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}
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}
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}
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// printf("\n");
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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() / SDR_RX_SCALEF);
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break;
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case 1:
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scopeSample.real(ci.imag() / SDR_RX_SCALEF);
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break;
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case 2:
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scopeSample.real(magsq);
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break;
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case 3:
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scopeSample.real(fmDemod);
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break;
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case 4:
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scopeSample.real(filt);
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break;
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case 5:
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scopeSample.real(m_rxBuf[m_rxBufIdx]);
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break;
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case 6:
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scopeSample.real(corr / 100.0);
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break;
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case 7:
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scopeSample.real(thresholdMet);
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break;
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case 8:
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scopeSample.real(gotSOP);
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break;
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case 9:
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scopeSample.real(dcOffset);
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break;
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case 10:
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scopeSample.real(scopeCRCValid ? 1.0 : (scopeCRCInvalid ? -1.0 : 0));
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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() / SDR_RX_SCALEF);
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break;
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case 1:
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scopeSample.imag(ci.imag() / SDR_RX_SCALEF);
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break;
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case 2:
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scopeSample.imag(magsq);
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break;
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case 3:
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scopeSample.imag(fmDemod);
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break;
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case 4:
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scopeSample.imag(filt);
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break;
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case 5:
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scopeSample.imag(m_rxBuf[m_rxBufIdx]);
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break;
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case 6:
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scopeSample.imag(corr / 100.0);
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break;
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case 7:
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scopeSample.imag(thresholdMet);
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break;
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case 8:
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scopeSample.imag(gotSOP);
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break;
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case 9:
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scopeSample.imag(dcOffset);
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break;
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case 10:
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scopeSample.imag(scopeCRCValid ? 1.0 : (scopeCRCInvalid ? -1.0 : 0));
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break;
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}
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sampleToScope(scopeSample);
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// Send demod signal to Demod Analzyer feature
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m_demodBuffer[m_demodBufferFill++] = fmDemod * std::numeric_limits<int16_t>::max();
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if (m_demodBufferFill >= m_demodBuffer.size())
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{
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QList<ObjectPipe*> dataPipes;
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MainCore::instance()->getDataPipes().getDataPipes(m_channel, "demod", dataPipes);
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if (dataPipes.size() > 0)
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{
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QList<ObjectPipe*>::iterator it = dataPipes.begin();
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for (; it != dataPipes.end(); ++it)
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{
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DataFifo *fifo = qobject_cast<DataFifo*>((*it)->m_element);
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if (fifo) {
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fifo->write((quint8*) &m_demodBuffer[0], m_demodBuffer.size() * sizeof(qint16), DataFifo::DataTypeI16);
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}
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}
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}
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m_demodBufferFill = 0;
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}
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}
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// Correlate received signal with training sequence
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// Note that DC offset doesn't matter for this
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Real RadiosondeDemodSink::correlate(int idx) const
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{
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Real corr = 0.0f;
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for (int i = 0; i < m_correlationLength; i++)
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{
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int j = (idx + i) % m_rxBufLength;
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corr += m_train[i] * m_rxBuf[j];
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}
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return corr;
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}
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bool RadiosondeDemodSink::processFrame(int length, float corr, int sampleIdx)
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{
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// Descramble
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for (int i = 0; i < length; i++) {
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m_bytes[i] = m_bytes[i] ^ m_descramble[i & 0x3f];
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}
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// Reed-Solomon Error Correction
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int errorsCorrected = reedSolomonErrorCorrection();
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if (errorsCorrected >= 0)
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{
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// Check per-block CRCs are correct
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if (checkCRCs(length))
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{
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if (getMessageQueueToChannel())
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{
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QByteArray rxPacket((char *)m_bytes, length);
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RadiosondeDemod::MsgMessage *msg = RadiosondeDemod::MsgMessage::create(rxPacket, errorsCorrected, corr);
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getMessageQueueToChannel()->push(msg);
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}
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// Skip over received packet, so we don't try to re-demodulate it
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m_rxBufCnt -= sampleIdx;
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return true;
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}
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}
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return false;
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}
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// Reed Solomon error correction
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// Returns number of errors corrected, or -1 if there are uncorrectable errors
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int RadiosondeDemodSink::reedSolomonErrorCorrection()
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{
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ReedSolomon::RS<RS41_RS_N,RS41_RS_K> rs;
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int errorsCorrected = 0;
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for (int i = 0; (i < RS41_RS_INTERLEAVE) && (errorsCorrected >= 0); i++)
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{
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// Deinterleave and reverse order
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uint8_t rsData[RS41_RS_N];
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memset(rsData, 0, RS41_RS_PAD);
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for (int j = 0; j < RS41_RS_DATA; j++) {
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rsData[RS41_RS_K-1-j] = m_bytes[RS41_OFFSET_FRAME_TYPE+j*RS41_RS_INTERLEAVE+i];
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}
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for (int j = 0; j < RS41_RS_2T; j++) {
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rsData[RS41_RS_N-1-j] = m_bytes[RS41_OFFSET_RS+i*RS41_RS_2T+j];
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}
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// Detect and correct errors
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int errors = rs.decode(&rsData[0], RS41_RS_K); // FIXME: Indicate 0 padding?
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if (errors >= 0) {
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errorsCorrected += errors;
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} else {
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// Uncorrectable errors
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return -1;
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}
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// Restore corrected data
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for (int j = 0; j < RS41_RS_DATA; j++) {
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m_bytes[RS41_OFFSET_FRAME_TYPE+j*RS41_RS_INTERLEAVE+i] = rsData[RS41_RS_K-1-j];
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}
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}
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return errorsCorrected;
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}
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// Check per-block CRCs
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// We could pass partial frames that have some correct CRCs, but for now, whole frame has to be correct
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bool RadiosondeDemodSink::checkCRCs(int length)
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{
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for (int i = RS41_OFFSET_BLOCK_0; i < length; )
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{
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uint8_t blockLength = m_bytes[i+1];
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uint16_t rxCrc = m_bytes[i+2+blockLength] | (m_bytes[i+2+blockLength+1] << 8);
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// CRC doesn't include ID/len - so these can be wrong
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m_crc.init();
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m_crc.calculate(&m_bytes[i+2], blockLength);
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uint16_t calcCrc = m_crc.get();
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if (calcCrc != rxCrc) {
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return false;
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}
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i += blockLength+4;
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}
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return true;
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}
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void RadiosondeDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
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{
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qDebug() << "RadiosondeDemodSink::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)
|
|
{
|
|
m_interpolator.create(16, channelSampleRate, m_settings.m_rfBandwidth / 2.2);
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|
m_interpolatorDistance = (Real) channelSampleRate / (Real) RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE;
|
|
m_interpolatorDistanceRemain = m_interpolatorDistance;
|
|
}
|
|
|
|
m_channelSampleRate = channelSampleRate;
|
|
m_channelFrequencyOffset = channelFrequencyOffset;
|
|
m_samplesPerSymbol = RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE / m_settings.m_baud;
|
|
qDebug() << "RadiosondeDemodSink::applyChannelSettings: m_samplesPerSymbol: " << m_samplesPerSymbol;
|
|
}
|
|
|
|
void RadiosondeDemodSink::applySettings(const RadiosondeDemodSettings& settings, bool force)
|
|
{
|
|
qDebug() << "RadiosondeDemodSink::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) RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE;
|
|
m_interpolatorDistanceRemain = m_interpolatorDistance;
|
|
m_lowpass.create(301, RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE, settings.m_rfBandwidth / 2.0f);
|
|
}
|
|
if ((settings.m_fmDeviation != m_settings.m_fmDeviation) || force)
|
|
{
|
|
m_phaseDiscri.setFMScaling(RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE / (2.0f * settings.m_fmDeviation));
|
|
}
|
|
|
|
if ((settings.m_baud != m_settings.m_baud) || force)
|
|
{
|
|
m_samplesPerSymbol = RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE / settings.m_baud;
|
|
qDebug() << "RadiosondeDemodSink::applySettings: m_samplesPerSymbol: " << m_samplesPerSymbol << " baud " << settings.m_baud;
|
|
|
|
// What value to use for BT? RFIC is Si4032 - its datasheet only appears to support 0.5
|
|
m_pulseShape.create(0.5, 3, m_samplesPerSymbol);
|
|
|
|
// Recieve buffer, long enough for one max length message
|
|
delete[] m_rxBuf;
|
|
m_rxBufLength = RADIOSONDEDEMOD_MAX_BYTES*8*m_samplesPerSymbol;
|
|
m_rxBuf = new Real[m_rxBufLength];
|
|
m_rxBufIdx = 0;
|
|
m_rxBufCnt = 0;
|
|
|
|
// Create training sequence for correlation
|
|
delete[] m_train;
|
|
|
|
const int correlateBits = 200; // Preamble is 320bits - leave some for AGC (and clock recovery eventually)
|
|
m_correlationLength = correlateBits*m_samplesPerSymbol; // Don't want to use header, as we want to calculate DC offset
|
|
m_train = new Real[m_correlationLength]();
|
|
|
|
// Pulse shape filter takes a few symbols before outputting expected shape
|
|
for (int j = 0; j < m_samplesPerSymbol; j++) {
|
|
m_pulseShape.filter(-1.0f);
|
|
}
|
|
for (int j = 0; j < m_samplesPerSymbol; j++) {
|
|
m_pulseShape.filter(1.0f);
|
|
}
|
|
for (int i = 0; i < correlateBits; i++)
|
|
{
|
|
for (int j = 0; j < m_samplesPerSymbol; j++) {
|
|
m_train[i*m_samplesPerSymbol+j] = -m_pulseShape.filter((i&1) * 2.0f - 1.0f);
|
|
}
|
|
}
|
|
}
|
|
|
|
m_settings = settings;
|
|
}
|