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more work on new clock recovery

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AlexandreRouma
2024-02-08 14:17:35 +01:00
parent 63aa45de9e
commit daf0f8c159
3 changed files with 75 additions and 18 deletions
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4
decoder_modules/pager_decoder/src/pocsag/decoder.h
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@@ -13,7 +13,7 @@
class POCSAGDecoder : public Decoder {
public:
POCSAGDecoder(const std::string& name, VFOManager::VFO* vfo) : diag(0.6, 320) {
POCSAGDecoder(const std::string& name, VFOManager::VFO* vfo) : diag(0.6, 544) {
this->name = name;
this->vfo = vfo;
@@ -26,7 +26,7 @@ public:
vfo->setBandwidthLimits(12500, 12500, true);
vfo->setSampleRate(SAMPLERATE, 12500);
dsp.init(vfo->output, SAMPLERATE, BAUDRATE);
reshape.init(&dsp.soft, 320, 0);
reshape.init(&dsp.soft, 544, 0);
dataHandler.init(&dsp.out, _dataHandler, this);
diagHandler.init(&reshape.out, _diagHandler, this);

2
decoder_modules/pager_decoder/src/pocsag/dsp.h
View File

@@ -112,7 +112,7 @@ public:
fir.init(NULL, shape);
//recov.init(NULL, samplerate/baudrate, 1e-4, 1.0, 0.05);
cs.init(NULL, PATTERN_DSDSDZED, sizeof(PATTERN_DSDSDZED)/sizeof(float), 0, 10);
cs.init(NULL, PATTERN_DSDSDZED, sizeof(PATTERN_DSDSDZED)/sizeof(float), 544, 10);
// Free useless buffers
// dcBlock.out.free();

87
decoder_modules/pager_decoder/src/pocsag/packet_clock_sync.h
View File

@@ -43,6 +43,7 @@ namespace dsp {
this->sampsPerSym = sampsPerSym;
this->threshold = threshold;
this->patternLen = patternLen;
this->frameLen = frameLen;
// Plan FFT
plan = fftwf_plan_dft_r2c_1d(fftSize, fftIn, (fftwf_complex*)fftOut, FFTW_ESTIMATE);
@@ -59,11 +60,16 @@ namespace dsp {
// Normalize the amplitudes
float maxAmp = 0.0f;
for (int i = 0; i < patternLen; i++) {
for (int i = 0; i < fftSize/2; i++) {
if (patternFFTAmps[i] > maxAmp) { maxAmp = patternFFTAmps[i]; }
}
volk_32f_s32f_multiply_32f(patternFFTAmps, patternFFTAmps, 1.0f/maxAmp, fftSize);
// Initialize the phase control loop
float omegaRelLimit = 0.05;
pcl.init(1, 10e-4, 0.0, 0.0, 1.0, sampsPerSym, sampsPerSym * (1.0 - omegaRelLimit), sampsPerSym * (1.0 + omegaRelLimit));
generateInterpTaps();
// Init base
base_type::init(in);
}
@@ -72,21 +78,55 @@ namespace dsp {
// Copy to buffer
memcpy(bufferStart, in, count * sizeof(float));
int outCount = 0;
bool first = true;
int outCount = 0;
for (int i = 0; i < count;) {
// Run clock recovery if needed
while (toRead) {
// Interpolate symbol
float symbol;
int phase = std::clamp<int>(floorf(pcl.phase * (float)interpPhaseCount), 0, interpPhaseCount - 1);
volk_32f_x2_dot_prod_32f(&symbol, &buffer[offsetInt], interpBank.phases[phase], interpTapCount);
out[outCount++] = symbol;
// Compute symbol phase error
float error = (math::step(lastSymbol) * symbol) - (lastSymbol * math::step(symbol));
lastSymbol = symbol;
// Clamp symbol phase error
if (error > 1.0f) { error = 1.0f; }
if (error < -1.0f) { error = -1.0f; }
// Advance symbol offset and phase
pcl.advance(error);
float delta = floorf(pcl.phase);
offsetInt += delta;
i = offsetInt;
pcl.phase -= delta;
// Decrement read counter
toRead--;
if (offsetInt >= count) {
offsetInt -= count;
break;
}
}
for (int i = 0; i < count; i++) {
// Measure correlation to the sync pattern
float corr;
volk_32f_x2_dot_prod_32f(&corr, &buffer[i], pattern, patternLen);
// If not correlated enough, go to next sample. Otherwise continue with fine detection
if (corr/(float)patternLen < threshold) { continue; }
if (corr/(float)patternLen < threshold) {
i++;
continue;
}
// Copy samples into FFT input (only the part where we think the pattern is located)
// TODO: Instead, check the interval onto which correlation occurs to determine where the pattern is located (IMPORTANT)
memcpy(fftIn, &buffer[i], patternLen*sizeof(float));
memset(&fftIn[patternLen], 0, (fftSize-patternLen)*sizeof(float)); // TODO, figure out why we need this
// Compute FFT
fftwf_execute(plan);
@@ -113,15 +153,15 @@ namespace dsp {
// Compute the total offset
float offset = (float)i - avgRate*(float)fftSize/(2.0f*FL_M_PI);
flog::debug("Detected: {} -> {}", i, offset);
if (first) {
outCount = 320;
memcpy(out, &buffer[(int)roundf(offset)], 320*sizeof(float));
first = false;
}
// Initialize clock recovery
offsetInt = floorf(offset) - 3; // TODO: Will be negative sometimes, has to be taken into account
pcl.phase = offset - (float)floorf(offset);
pcl.freq = sampsPerSym;
flog::debug("Detected: {} -> {} ({})", i, offset, avgRate);
// Start reading symbols
toRead = frameLen;
}
// Move unused data
@@ -137,11 +177,20 @@ namespace dsp {
count = process(count, base_type::_in->readBuf, base_type::out.writeBuf);
base_type::_in->flush();
//if (!base_type::out.swap(count)) { return -1; }
if (count) {
if (!base_type::out.swap(count)) { return -1; }
}
return count;
}
private:
void generateInterpTaps() {
double bw = 0.5 / (double)interpPhaseCount;
dsp::tap<float> lp = dsp::taps::windowedSinc<float>(interpPhaseCount * interpTapCount, dsp::math::hzToRads(bw, 1.0), dsp::window::nuttall, interpPhaseCount);
interpBank = dsp::multirate::buildPolyphaseBank<float>(interpPhaseCount, lp);
taps::free(lp);
}
int delayLen;
float* buffer = NULL;
float* bufferStart = NULL;
@@ -149,7 +198,7 @@ namespace dsp {
int patternLen;
bool locked;
int fftSize;
int frameLen;
float threshold;
float* fftIn = NULL;
@@ -160,5 +209,13 @@ namespace dsp {
float* patternFFTAmps;
float sampsPerSym;
int toRead = 0;
loop::PhaseControlLoop<float, false> pcl;
dsp::multirate::PolyphaseBank<float> interpBank;
int interpTapCount = 8;
int interpPhaseCount = 128;
float lastSymbol = 0.0f;
int offsetInt;
};
}