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https://github.com/jankae/LibreVNA.git
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Basic DFT spectrum analysis working
This commit is contained in:
Jan Käberich
parent
f889ec854b
commit
ce475fa042
27 changed files with 1313 additions and 563 deletions
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@ -11,6 +11,8 @@
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#define LOG_MODULE "SA"
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#include "Log.h"
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using namespace HWHAL;
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static Protocol::SpectrumAnalyzerSettings s;
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static uint32_t pointCnt;
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static uint32_t points;
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@ -21,10 +23,11 @@ static Protocol::PacketInfo p;
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static bool active = false;
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static uint32_t lastLO2;
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static uint32_t actualRBW;
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static bool usingDFT;
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static uint16_t DFTpoints;
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static bool negativeDFT; // if true, a positive frequency shift at input results in a negative shift at the 2.IF. Handle DFT accordingly
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static float port1Measurement, port2Measurement;
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using namespace HWHAL;
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static float port1Measurement[FPGA::DFTbins], port2Measurement[FPGA::DFTbins];
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static void StartNextSample() {
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uint64_t freq = s.f_start + (s.f_stop - s.f_start) * pointCnt / (points - 1);
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@ -34,16 +37,20 @@ static void StartNextSample() {
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case 0:
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default:
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// reset minimum amplitudes in first signal ID step
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port1Measurement = std::numeric_limits<float>::max();
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port2Measurement = std::numeric_limits<float>::max();
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for (uint16_t i = 0; i < DFTpoints; i++) {
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port1Measurement[i] = std::numeric_limits<float>::max();
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port2Measurement[i] = std::numeric_limits<float>::max();
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}
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// Use default LO frequencies
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LO1freq = freq + HW::IF1;
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LO2freq = HW::IF1 - HW::IF2;
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FPGA::WriteRegister(FPGA::Reg::ADCPrescaler, 112);
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FPGA::WriteRegister(FPGA::Reg::PhaseIncrement, 1120);
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negativeDFT = true;
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break;
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case 1:
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LO2freq = HW::IF1 - HW::IF2;
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negativeDFT = false;
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// Shift first LO to other side
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// depending on the measurement frequency this is not possible or additive mixing has to be used
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if(freq >= HW::IF1 + HW::LO1_minFreq) {
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@ -59,13 +66,15 @@ static void StartNextSample() {
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signalIDstep++;
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/* no break */
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case 2:
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// Shift both LOs to other side
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// Shift second LOs to other side
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LO1freq = freq + HW::IF1;
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LO2freq = HW::IF1 + HW::IF2;
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negativeDFT = false;
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break;
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case 3:
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// Shift both LO to other side
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LO2freq = HW::IF1 + HW::IF2;
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// Shift second LO to other side
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negativeDFT = true;
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// depending on the measurement frequency this is not possible or additive mixing has to be used
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if(freq >= HW::IF1 + HW::LO1_minFreq) {
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// frequency is high enough to shift 1.LO below measurement frequency
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@ -81,6 +90,7 @@ static void StartNextSample() {
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/* no break */
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case 4:
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// Use default frequencies with different ADC samplerate to remove images in final IF
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negativeDFT = true;
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LO1freq = freq + HW::IF1;
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LO2freq = HW::IF1 - HW::IF2;
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FPGA::WriteRegister(FPGA::Reg::ADCPrescaler, 120);
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@ -96,6 +106,17 @@ static void StartNextSample() {
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Si5351.SetCLK(SiChannel::Port2LO2, LO2freq, Si5351C::PLL::B, Si5351C::DriveStrength::mA2);
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lastLO2 = LO2freq;
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}
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if (usingDFT) {
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uint32_t spacing = (s.f_stop - s.f_start) / (points - 1);
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uint32_t start = HW::IF2;
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if(negativeDFT) {
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// needs to look below the start frequency, shift start
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start -= spacing * (DFTpoints - 1);
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}
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FPGA::SetupDFT(start, spacing);
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FPGA::StartDFT();
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}
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// Configure the sampling in the FPGA
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FPGA::WriteSweepConfig(0, 0, Source.GetRegisters(), LO1.GetRegisters(), 0,
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0, FPGA::SettlingTime::us20, FPGA::Samples::SPPRegister, 0,
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@ -111,9 +132,6 @@ void SA::Setup(Protocol::SpectrumAnalyzerSettings settings) {
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s = settings;
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HW::SetMode(HW::Mode::SA);
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FPGA::SetMode(FPGA::Mode::FPGA);
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FPGA::DisableInterrupt(FPGA::Interrupt::NewData);
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FPGA::DisableInterrupt(FPGA::Interrupt::SweepHalted);
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FPGA::EnableInterrupt(FPGA::Interrupt::DFTReady);
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// in almost all cases a full sweep requires more points than the FPGA can handle at a time
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// individually start each point and do the sweep in the uC
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FPGA::SetNumberOfPoints(1);
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@ -148,12 +166,17 @@ void SA::Setup(Protocol::SpectrumAnalyzerSettings settings) {
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FPGA::Enable(FPGA::Periphery::Port1Mixer);
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FPGA::Enable(FPGA::Periphery::Port2Mixer);
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// Configure DFT
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LOG_INFO("DFT samples: %lu", sampleNum);
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FPGA::WriteRegister(FPGA::Reg::DFTSamples, sampleNum - 1);
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FPGA::WriteRegister(FPGA::Reg::DFTWindowInc, 65536 / sampleNum);
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FPGA::WriteRegister(FPGA::Reg::DFTFirstBin, 17920);
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FPGA::WriteRegister(FPGA::Reg::DFTFreqSpacing, 1147);
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// automatically select DFT mode for lower RBWs
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usingDFT = actualRBW <= 1000;
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if (usingDFT) {
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DFTpoints = FPGA::DFTbins; // use full DFT in FPGA
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FPGA::DisableInterrupt(FPGA::Interrupt::NewData);
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} else {
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DFTpoints = 1; // can only measure one point at a time
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FPGA::StopDFT();
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FPGA::EnableInterrupt(FPGA::Interrupt::NewData);
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}
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lastLO2 = 0;
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active = true;
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@ -166,26 +189,39 @@ bool SA::MeasurementDone(const FPGA::SamplingResult &result) {
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}
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FPGA::AbortSweep();
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uint16_t i=0;
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while(FPGA::GetStatus() & (uint16_t) FPGA::Interrupt::DFTReady) {
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auto dft = FPGA::ReadDFTResult();
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dft.P1 /= sampleNum;
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dft.P2 /= sampleNum;
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LOG_INFO("DFT %d: %lu, %lu", i, (uint32_t) dft.P1, (uint32_t) dft.P2);
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Log_Flush();
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i++;
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}
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FPGA::DisableInterrupt(FPGA::Interrupt::DFTReady);
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FPGA::EnableInterrupt(FPGA::Interrupt::DFTReady);
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for(uint16_t i=0;i<DFTpoints;i++) {
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float port1, port2;
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if (usingDFT) {
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// use DFT result
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auto dft = FPGA::ReadDFTResult();
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port1 = dft.P1;
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port2 = dft.P2;
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} else {
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port1 = abs(std::complex<float>(result.P1I, result.P1Q));
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port2 = abs(std::complex<float>(result.P2I, result.P2Q));
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}
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port1 /= sampleNum;
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port2 /= sampleNum;
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float port1 = abs(std::complex<float>(result.P1I, result.P1Q))/sampleNum;
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float port2 = abs(std::complex<float>(result.P2I, result.P2Q))/sampleNum;
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if(port1 < port1Measurement) {
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port1Measurement = port1;
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uint16_t index = i;
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if (negativeDFT) {
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// bin order is reversed
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index = DFTpoints - i - 1;
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}
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if(port1 < port1Measurement[index]) {
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port1Measurement[index] = port1;
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}
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if(port2 < port2Measurement[index]) {
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port2Measurement[index] = port2;
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}
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}
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if(port2 < port2Measurement) {
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port2Measurement = port2;
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if (usingDFT) {
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FPGA::StopDFT();
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// will be started again in StartNextSample
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}
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// trigger work function
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return true;
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}
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@ -196,74 +232,76 @@ void SA::Work() {
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}
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if(!s.SignalID || signalIDstep >= 4) {
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// this measurement point is done, handle result according to detector
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uint16_t binIndex = pointCnt / binSize;
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uint32_t pointInBin = pointCnt % binSize;
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bool lastPointInBin = pointInBin >= binSize - 1;
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auto det = (Detector) s.Detector;
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if(det == Detector::Normal) {
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det = binIndex & 0x01 ? Detector::PosPeak : Detector::NegPeak;
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}
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switch(det) {
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case Detector::PosPeak:
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if(pointInBin == 0) {
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p.spectrumResult.port1 = std::numeric_limits<float>::min();
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p.spectrumResult.port2 = std::numeric_limits<float>::min();
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for(uint16_t i=0;i<DFTpoints;i++) {
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uint16_t binIndex = (pointCnt + i) / binSize;
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uint32_t pointInBin = (pointCnt + i) % binSize;
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bool lastPointInBin = pointInBin >= binSize - 1;
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auto det = (Detector) s.Detector;
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if(det == Detector::Normal) {
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det = binIndex & 0x01 ? Detector::PosPeak : Detector::NegPeak;
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}
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if(port1Measurement > p.spectrumResult.port1) {
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p.spectrumResult.port1 = port1Measurement;
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switch(det) {
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case Detector::PosPeak:
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if(pointInBin == 0) {
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p.spectrumResult.port1 = std::numeric_limits<float>::min();
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p.spectrumResult.port2 = std::numeric_limits<float>::min();
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}
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if(port1Measurement[i] > p.spectrumResult.port1) {
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p.spectrumResult.port1 = port1Measurement[i];
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}
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if(port2Measurement[i] > p.spectrumResult.port2) {
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p.spectrumResult.port2 = port2Measurement[i];
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}
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break;
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case Detector::NegPeak:
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if(pointInBin == 0) {
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p.spectrumResult.port1 = std::numeric_limits<float>::max();
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p.spectrumResult.port2 = std::numeric_limits<float>::max();
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}
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if(port1Measurement[i] < p.spectrumResult.port1) {
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p.spectrumResult.port1 = port1Measurement[i];
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}
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if(port2Measurement[i] < p.spectrumResult.port2) {
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p.spectrumResult.port2 = port2Measurement[i];
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}
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break;
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case Detector::Sample:
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if(pointInBin <= binSize / 2) {
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// still in first half of bin, simply overwrite
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p.spectrumResult.port1 = port1Measurement[i];
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p.spectrumResult.port2 = port2Measurement[i];
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}
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break;
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case Detector::Average:
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if(pointInBin == 0) {
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p.spectrumResult.port1 = 0;
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p.spectrumResult.port2 = 0;
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}
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p.spectrumResult.port1 += port1Measurement[i];
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p.spectrumResult.port2 += port2Measurement[i];
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if(lastPointInBin) {
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// calculate average
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p.spectrumResult.port1 /= binSize;
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p.spectrumResult.port2 /= binSize;
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}
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break;
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case Detector::Normal:
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// nothing to do, normal detector handled by PosPeak or NegPeak in each sample
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break;
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}
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if(port2Measurement > p.spectrumResult.port2) {
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p.spectrumResult.port2 = port2Measurement;
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}
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break;
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case Detector::NegPeak:
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if(pointInBin == 0) {
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p.spectrumResult.port1 = std::numeric_limits<float>::max();
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p.spectrumResult.port2 = std::numeric_limits<float>::max();
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}
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if(port1Measurement < p.spectrumResult.port1) {
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p.spectrumResult.port1 = port1Measurement;
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}
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if(port2Measurement < p.spectrumResult.port2) {
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p.spectrumResult.port2 = port2Measurement;
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}
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break;
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case Detector::Sample:
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if(pointInBin <= binSize / 2) {
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// still in first half of bin, simply overwrite
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p.spectrumResult.port1 = port1Measurement;
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p.spectrumResult.port2 = port2Measurement;
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}
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break;
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case Detector::Average:
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if(pointInBin == 0) {
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p.spectrumResult.port1 = 0;
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p.spectrumResult.port2 = 0;
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}
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p.spectrumResult.port1 += port1Measurement;
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p.spectrumResult.port2 += port2Measurement;
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if(lastPointInBin) {
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// calculate average
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p.spectrumResult.port1 /= binSize;
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p.spectrumResult.port2 /= binSize;
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// Send result to application
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p.type = Protocol::PacketType::SpectrumAnalyzerResult;
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// measurements are already up to date, fill remaining fields
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p.spectrumResult.pointNum = binIndex;
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p.spectrumResult.frequency = s.f_start + (s.f_stop - s.f_start) * binIndex / (s.pointNum - 1);
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Communication::Send(p);
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}
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break;
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case Detector::Normal:
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// nothing to do, normal detector handled by PosPeak or NegPeak in each sample
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break;
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}
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if(lastPointInBin) {
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// Send result to application
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p.type = Protocol::PacketType::SpectrumAnalyzerResult;
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// measurements are already up to date, fill remaining fields
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p.spectrumResult.pointNum = binIndex;
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p.spectrumResult.frequency = s.f_start + (s.f_stop - s.f_start) * binIndex / (s.pointNum - 1);
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Communication::Send(p);
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}
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// setup for next step
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signalIDstep = 0;
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if(pointCnt < points - 1) {
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pointCnt++;
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if(pointCnt < points - DFTpoints) {
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pointCnt += DFTpoints;
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} else {
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pointCnt = 0;
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}
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