Identify Chirp Spread Spectrum Signals

[alphapats]

I want to modify the code of gqrx to automatically identify the peaks of LoRAWAN (Chirp Spread Signals) in the spectrum. Presently I am able to identify only peaks of NB sigs and same code is identifying multiple peaks for same LoRAWAN signal. Can someone help me with the relevant sections of code where I can carryout these modifications?

[argilo]

If you'd like to experiment with the peak detection algorithm, you can find the code in plotter.cpp:

gqrx/src/qtgui/plotter.cpp

Lines 1638 to 1738 in 848acef

	// Peak detection
	if (m_PeakDetectActive)
	{
	const int pw = PEAK_WINDOW_HALF_WIDTH;
	// Use data source appropriate for current display mode
	float *_detectSource;
	if (m_MaxHoldActive)
	_detectSource = m_fftMaxHoldBuf;
	else if (m_PlotMode == PLOT_MODE_AVG)
	_detectSource = m_fftAvgBuf;
	else
	_detectSource = m_fftMaxBuf;
	const float *detectSource = _detectSource;
	// Run peak detection periodically. If overlay will be redrawn, run
	// peak detection since zoom/pan may have changed.
	if (tnow_ms > tlast_peaks_ms + PEAK_UPDATE_PERIOD || m_DrawOverlay) {
	tlast_peaks_ms = tnow_ms;
	m_Peaks.clear();
	// Narrow peaks
	for (i = pw; i < npts - pw; ++i) {
	const int ix = i + xmin;
	const float vi = detectSource[ix];
	float sumV = 0;
	float minV = vi;
	float maxV = 0;
	for (j = -pw; j <= pw; ++j) {
	const float vj = detectSource[ix + j];
	minV = std::min(minV, vj);
	maxV = std::max(maxV, vj);
	sumV += vj;
	}
	const float avgV = sumV / (float)(pw * 2 + 1);
	m_peakSmoothBuf[ix] = avgV;
	if (vi == maxV && (vi > 2.0f * avgV) && (vi > 4.0f * minV))
	{
	const qreal y = (qreal)std::max(std::min(
	panddBGainFactor * (m_PandMaxdB - 10.0f * log10f(vi)),
	(float)plotHeight - 0.0f), 0.0f);
	m_Peaks[ix] = y;
	}
	}
	// Use the smoothed curve to find wider peaks
	const int pw2 = pw * 5;
	for (i = pw2; i < npts - pw2; ++i) {
	const int ix = i + xmin;
	const float vi = m_peakSmoothBuf[ix];
	float sumV = 0;
	float minV = vi;
	float maxV = 0;
	for (j = -pw2; j <= pw2; ++j) {
	const float vj = m_peakSmoothBuf[ix + j];
	minV = std::min(minV, vj);
	maxV = std::max(maxV, vj);
	sumV += vj;
	}
	const float avgV = sumV / (float)(pw2 * 2);
	if (vi == maxV && (vi > 2.0f * avgV) && (vi > 4.0f * minV))
	{
	const qreal y = (qreal)std::max(std::min(
	panddBGainFactor * (m_PandMaxdB - 10.0f * log10f(vi)),
	(float)plotHeight - 0.0f), 0.0f);
	// Show the wider peak only if there is no very close narrow peak
	bool found = false;
	for (j = -pw; j <= pw; ++j) {
	auto it = m_Peaks.find(ix + j);
	if (it != m_Peaks.end()) {
	found = true;
	break;
	}
	}
	if (!found) {
	m_Peaks[ix] = y;
	}
	}
	}
	}
	// Paint peaks with shadow
	QPen peakPen(m_maxFftColor, m_DPR);
	QPen peakShadowPen(Qt::black, m_DPR);
	peakPen.setWidthF(m_DPR);
	for(auto peakx : m_Peaks.keys()) {
	const qreal peakxPlot = (qreal)peakx;
	const qreal peakv = m_Peaks.value(peakx);
	painter2.setPen(peakShadowPen);
	painter2.drawEllipse(
	QRectF(peakxPlot - 5.0 * m_DPR + shadowOffset,
	peakv - 5.0 * m_DPR + shadowOffset,
	10.0 * m_DPR, 10.0 * m_DPR));
	painter2.setPen(peakPen);
	painter2.drawEllipse(
	QRectF(peakxPlot - 5.0 * m_DPR,
	peakv - 5.0 * m_DPR,
	10.0 * m_DPR, 10.0 * m_DPR));
	}
	}

[alphapats]

Thanks, will try that