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sdrangel/plugins/channelrx/demodradiosonde/radiosondedemodsink.cpp
2022-07-24 21:48:02 +02:00

570 lines
20 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2019 Edouard Griffiths, F4EXB //
// Copyright (C) 2021 Jon Beniston, M7RCE //
// //
// 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 "dsp/scopevis.h"
#include "util/db.h"
#include "util/stepfunctions.h"
#include "util/reedsolomon.h"
#include "maincore.h"
#include "radiosondedemod.h"
#include "radiosondedemodsink.h"
const uint8_t RadiosondeDemodSink::m_descramble[64] = {
0x96, 0x83, 0x3E, 0x51, 0xB1, 0x49, 0x08, 0x98,
0x32, 0x05, 0x59, 0x0E, 0xF9, 0x44, 0xC6, 0x26,
0x21, 0x60, 0xC2, 0xEA, 0x79, 0x5D, 0x6D, 0xA1,
0x54, 0x69, 0x47, 0x0C, 0xDC, 0xE8, 0x5C, 0xF1,
0xF7, 0x76, 0x82, 0x7F, 0x07, 0x99, 0xA2, 0x2C,
0x93, 0x7C, 0x30, 0x63, 0xF5, 0x10, 0x2E, 0x61,
0xD0, 0xBC, 0xB4, 0xB6, 0x06, 0xAA, 0xF4, 0x23,
0x78, 0x6E, 0x3B, 0xAE, 0xBF, 0x7B, 0x4C, 0xC1
};
RadiosondeDemodSink::RadiosondeDemodSink(RadiosondeDemod *radiosondeDemod) :
m_scopeSink(nullptr),
m_radiosondeDemod(radiosondeDemod),
m_channelSampleRate(RadiosondeDemodSettings::RADIOSONDEDEMOD_CHANNEL_SAMPLE_RATE),
m_channelFrequencyOffset(0),
m_magsqSum(0.0f),
m_magsqPeak(0.0f),
m_magsqCount(0),
m_messageQueueToChannel(nullptr),
m_rxBuf(nullptr),
m_train(nullptr),
m_sampleBufferIndex(0)
{
m_magsq = 0.0;
m_demodBuffer.resize(1<<12);
m_demodBufferFill = 0;
m_sampleBuffer.resize(m_sampleBufferSize);
applySettings(m_settings, true);
applyChannelSettings(m_channelSampleRate, m_channelFrequencyOffset, true);
}
RadiosondeDemodSink::~RadiosondeDemodSink()
{
delete[] m_rxBuf;
delete[] m_train;
}
void RadiosondeDemodSink::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 RadiosondeDemodSink::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 RadiosondeDemodSink::processOneSample(Complex &ci)
{
// 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++;
// Gaussian filter
Real filt = m_pulseShape.filter(fmDemod);
// An input frequency offset corresponds to a DC offset after FM demodulation
// What frequency offset is RS41 specified too?
// We need to remove this, otherwise it may effect the sampling
// To calculate what it is, we sum the training sequence, which should be zero
// Clip, as large noise can result in high correlation
// Don't clip to 1.0 - as there may be some DC offset (1k/4.8k max dev=0.2)
Real filtClipped;
filtClipped = std::fmax(-1.4, std::fmin(1.4, filt));
// Buffer filtered samples. We buffer enough samples for a max length message
// before trying to demod, so false triggering can't make us miss anything
m_rxBuf[m_rxBufIdx] = filtClipped;
m_rxBufIdx = (m_rxBufIdx + 1) % m_rxBufLength;
m_rxBufCnt = std::min(m_rxBufCnt + 1, m_rxBufLength);
Real corr = 0.0f;
bool scopeCRCValid = false;
bool scopeCRCInvalid = false;
Real dcOffset = 0.0f;
bool thresholdMet = false;
bool gotSOP = false;
if ((m_rxBufCnt >= m_rxBufLength))
{
// Correlate with training sequence
corr = correlate(m_rxBufIdx);
// If we meet threshold, try to demod
// Take abs value, to account for both initial phases
thresholdMet = fabs(corr) >= m_settings.m_correlationThreshold;
if (thresholdMet)
{
// Try to see if starting at a later sample improves correlation
int maxCorrOffset = 0;
Real maxCorr;
do
{
maxCorr = fabs(corr);
maxCorrOffset++;
corr = correlate(m_rxBufIdx + maxCorrOffset);
}
while (fabs(corr) > maxCorr);
maxCorrOffset--;
// Calculate mean of preamble as DC offset (as it should be 0 on an ideal signal)
Real trainingSum = 0.0f;
for (int i = 0; i < m_correlationLength; i++)
{
int j = (m_rxBufIdx + maxCorrOffset + i) % m_rxBufLength;
trainingSum += m_rxBuf[j];
}
dcOffset = trainingSum/m_correlationLength;
// Start demod after (most of) preamble
int x = (m_rxBufIdx + maxCorrOffset + m_correlationLength*3/4 + 0) % m_rxBufLength;
// Attempt to demodulate
uint64_t bits = 0;
int bitCount = 0;
int byteCount = 0;
QList<int> sampleIdxs;
for (int sampleIdx = 0; sampleIdx < m_rxBufLength; sampleIdx += m_samplesPerSymbol)
{
// Sum and slice
// Summing 3 samples seems to give a very small improvement vs just using 1
int sampleCnt = 3;
int sampleOffset = -1;
Real sampleSum = 0.0f;
for (int i = 0; i < sampleCnt; i++) {
sampleSum += m_rxBuf[(x + sampleOffset + i) % m_rxBufLength] - dcOffset;
sampleIdxs.append((x + sampleOffset + i) % m_rxBufLength);
}
int symbol = sampleSum >= 0.0f ? 1 : 0;
// Move to next symbol
x = (x + m_samplesPerSymbol) % m_rxBufLength;
// Symbols map directly to bits
int bit = symbol;
// Store in shift reg (little endian)
bits |= ((uint64_t)bit) << bitCount;
bitCount++;
if (gotSOP)
{
if (bitCount == 8)
{
// Got a complete byte
m_bytes[byteCount] = bits;
byteCount++;
bits = 0;
bitCount = 0;
if (byteCount >= RS41_LENGTH_STD)
{
// Get expected length of frame
uint8_t frameType = m_bytes[RS41_OFFSET_FRAME_TYPE] ^ m_descramble[RS41_OFFSET_FRAME_TYPE];
int length = RS41Frame::getFrameLength(frameType);
// Have we received a complete frame?
if (byteCount == length)
{
bool ok = processFrame(length, corr, sampleIdx);
scopeCRCValid = ok;
scopeCRCInvalid = !ok;
break;
}
}
}
}
else if (bits == 0xf812962211cab610ULL) // Scrambled header
{
// Start of packet
gotSOP = true;
bits = 0;
bitCount = 0;
m_bytes[0] = 0x10;
m_bytes[1] = 0xb6;
m_bytes[2] = 0xca;
m_bytes[3] = 0x11;
m_bytes[4] = 0x22;
m_bytes[5] = 0x96;
m_bytes[6] = 0x12;
m_bytes[7] = 0xf8;
byteCount = 8;
}
else
{
if (bitCount == 64)
{
bits >>= 1;
bitCount--;
}
if (sampleIdx >= 16 * 8 * m_samplesPerSymbol)
{
// Too many bits without receving header
break;
}
}
}
// printf("\n");
}
}
// Select signals to feed to scope
Complex scopeSample;
switch (m_settings.m_scopeCh1)
{
case 0:
scopeSample.real(ci.real() / SDR_RX_SCALEF);
break;
case 1:
scopeSample.real(ci.imag() / SDR_RX_SCALEF);
break;
case 2:
scopeSample.real(magsq);
break;
case 3:
scopeSample.real(fmDemod);
break;
case 4:
scopeSample.real(filt);
break;
case 5:
scopeSample.real(m_rxBuf[m_rxBufIdx]);
break;
case 6:
scopeSample.real(corr / 100.0);
break;
case 7:
scopeSample.real(thresholdMet);
break;
case 8:
scopeSample.real(gotSOP);
break;
case 9:
scopeSample.real(dcOffset);
break;
case 10:
scopeSample.real(scopeCRCValid ? 1.0 : (scopeCRCInvalid ? -1.0 : 0));
break;
}
switch (m_settings.m_scopeCh2)
{
case 0:
scopeSample.imag(ci.real() / SDR_RX_SCALEF);
break;
case 1:
scopeSample.imag(ci.imag() / SDR_RX_SCALEF);
break;
case 2:
scopeSample.imag(magsq);
break;
case 3:
scopeSample.imag(fmDemod);
break;
case 4:
scopeSample.imag(filt);
break;
case 5:
scopeSample.imag(m_rxBuf[m_rxBufIdx]);
break;
case 6:
scopeSample.imag(corr / 100.0);
break;
case 7:
scopeSample.imag(thresholdMet);
break;
case 8:
scopeSample.imag(gotSOP);
break;
case 9:
scopeSample.imag(dcOffset);
break;
case 10:
scopeSample.imag(scopeCRCValid ? 1.0 : (scopeCRCInvalid ? -1.0 : 0));
break;
}
sampleToScope(scopeSample);
// Send demod signal to Demod Analzyer feature
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;
}
}
// Correlate received signal with training sequence
// Note that DC offset doesn't matter for this
Real RadiosondeDemodSink::correlate(int idx) const
{
Real corr = 0.0f;
for (int i = 0; i < m_correlationLength; i++)
{
int j = (idx + i) % m_rxBufLength;
corr += m_train[i] * m_rxBuf[j];
}
return corr;
}
bool RadiosondeDemodSink::processFrame(int length, float corr, int sampleIdx)
{
// Descramble
for (int i = 0; i < length; i++) {
m_bytes[i] = m_bytes[i] ^ m_descramble[i & 0x3f];
}
// Reed-Solomon Error Correction
int errorsCorrected = reedSolomonErrorCorrection();
if (errorsCorrected >= 0)
{
// Check per-block CRCs are correct
if (checkCRCs(length))
{
if (getMessageQueueToChannel())
{
QByteArray rxPacket((char *)m_bytes, length);
RadiosondeDemod::MsgMessage *msg = RadiosondeDemod::MsgMessage::create(rxPacket, errorsCorrected, corr);
getMessageQueueToChannel()->push(msg);
}
// Skip over received packet, so we don't try to re-demodulate it
m_rxBufCnt -= sampleIdx;
return true;
}
}
return false;
}
// Reed Solomon error correction
// Returns number of errors corrected, or -1 if there are uncorrectable errors
int RadiosondeDemodSink::reedSolomonErrorCorrection()
{
ReedSolomon::RS<RS41_RS_N,RS41_RS_K> rs;
int errorsCorrected = 0;
for (int i = 0; (i < RS41_RS_INTERLEAVE) && (errorsCorrected >= 0); i++)
{
// Deinterleave and reverse order
uint8_t rsData[RS41_RS_N];
memset(rsData, 0, RS41_RS_PAD);
for (int j = 0; j < RS41_RS_DATA; j++) {
rsData[RS41_RS_K-1-j] = m_bytes[RS41_OFFSET_FRAME_TYPE+j*RS41_RS_INTERLEAVE+i];
}
for (int j = 0; j < RS41_RS_2T; j++) {
rsData[RS41_RS_N-1-j] = m_bytes[RS41_OFFSET_RS+i*RS41_RS_2T+j];
}
// Detect and correct errors
int errors = rs.decode(&rsData[0], RS41_RS_K); // FIXME: Indicate 0 padding?
if (errors >= 0) {
errorsCorrected += errors;
} else {
// Uncorrectable errors
return -1;
}
// Restore corrected data
for (int j = 0; j < RS41_RS_DATA; j++) {
m_bytes[RS41_OFFSET_FRAME_TYPE+j*RS41_RS_INTERLEAVE+i] = rsData[RS41_RS_K-1-j];
}
}
return errorsCorrected;
}
// Check per-block CRCs
// We could pass partial frames that have some correct CRCs, but for now, whole frame has to be correct
bool RadiosondeDemodSink::checkCRCs(int length)
{
for (int i = RS41_OFFSET_BLOCK_0; i < length; )
{
uint8_t blockLength = m_bytes[i+1];
uint16_t rxCrc = m_bytes[i+2+blockLength] | (m_bytes[i+2+blockLength+1] << 8);
// CRC doesn't include ID/len - so these can be wrong
m_crc.init();
m_crc.calculate(&m_bytes[i+2], blockLength);
uint16_t calcCrc = m_crc.get();
if (calcCrc != rxCrc) {
return false;
}
i += blockLength+4;
}
return true;
}
void RadiosondeDemodSink::applyChannelSettings(int channelSampleRate, int channelFrequencyOffset, bool force)
{
qDebug() << "RadiosondeDemodSink::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) 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;
}