I decided to include this because it has has bug fixes that aren't in the official driver. also the bug hadn't been fully squashed; i stomped on it.

.gitignore

@@ -6,7 +6,7 @@ build
 *.swp
 *.cmake
 requirements.txt
-ad5940.*
+ad5940
 pico_sdk_import.cmake
 build*
 *.png

Impedance.c

@@ -5,7 +5,7 @@
 #include "math.h"
 #include "Impedance.h"
 
-/* Default LPDAC resolution(2.5V internal reference). */
+/* Default LPDAC resolution (2.5V internal reference) */
 #define DAC12BITVOLT_1LSB   (2200.0f/4095)  // mV
 #define DAC6BITVOLT_1LSB    (DAC12BITVOLT_1LSB*64)  // mV
 
@@ -18,14 +18,14 @@ AppIMPCfg_Type AppIMPCfg =
   .SeqStartAddrCal = 0,
   .MaxSeqLenCal = 0,
 
-  .ImpODR = 20.0,             /* 20.0 Hz = 50ms period */
+  .ImpODR = 20.0,             /* Output Data Rate: 20.0 Hz */
-  .NumOfData = -1,
+  .NumOfData = -1,            /* -1 for infinite/continuous measurement */
-  .RealDataCount = -1,        /* Default to no filtering */
+  .RealDataCount = -1,        
   .SysClkFreq = 16000000.0,
-  .WuptClkFreq = 32000.0,
+  .WuptClkFreq = 32000.0,     /* Low Frequency Oscillator (LFO) typically 32kHz */
   .AdcClkFreq = 16000000.0,
-  .RcalVal = 10000.0,
+  .RcalVal = 10000.0,         /* Calibration Resistor Value (Ohms) */
-  .RtiaVal = 200.0,
+  .RtiaVal = 200.0,           /* TIA Gain Resistor Value (Ohms) */
 
   .DswitchSel = SWD_CE0,
   .PswitchSel = SWP_CE0,
@@ -39,14 +39,14 @@ AppIMPCfg_Type AppIMPCfg =
   .ExcitBufGain = EXCITBUFGAIN_0P25,
   .HsDacGain = HSDACGAIN_0P2,
   .HsDacUpdateRate = 7,
-  .DacVoltPP = 600.0,
+  .DacVoltPP = 600.0,         /* Excitation Amplitude (mV peak-to-peak) */
-  .BiasVolt = -0.0f,
+  .BiasVolt = -0.0f,          /* DC Bias Voltage */
 
-  .SinFreq = 1000.0,
+  .SinFreq = 1000.0,          /* Fixed Frequency (Hz) */
 
-  .DftNum = DFTNUM_16384,
+  .DftNum = DFTNUM_16384,     /* DFT Point Count */
   .DftSrc = DFTSRC_SINC3,
-  .HanWinEn = bTRUE,
+  .HanWinEn = bTRUE,          /* Hanning Window for spectral leakage reduction */
 
   .AdcPgaGain = ADCPGA_1P5,
   .ADCSinc3Osr = ADCSINC3OSR_2,
@@ -61,7 +61,7 @@ AppIMPCfg_Type AppIMPCfg =
   .SweepCfg.SweepLog = bFALSE,
   .SweepCfg.SweepIndex = 0,
 
-  .FifoThresh = 6, /* 3 measurements * 2 (Real/Imag) = 6 words */
+  .FifoThresh = 6,            /* Threshold: 3 measurements * 2 (Real/Imag) = 6 words */
   .IMPInited = bFALSE,
   .StopRequired = bFALSE,
 };
@@ -70,18 +70,21 @@ AppIMPCfg_Type AppIMPCfg =
 /* Helper Functions                                                        */
 /* ----------------------------------------------------------------------- */
 
+// Forward declaration to allow usage in AppIMPCtrl
+AD5940Err AppIMPCheckFreq(float freq);
+
 void AppIMPCleanup(void) {
     // Ensure chip is awake before sending commands
     if(AD5940_WakeUp(10) > 10) return;
 
-    // 1. Stop Sequencer and Wakeup Timer
+    // Stop Sequencer and Wakeup Timer
     AD5940_WUPTCtrl(bFALSE);
     AD5940_SEQCtrlS(bFALSE);
     
-    // 2. Stop any active conversions/WG, but KEEP Reference/LDOs ON
+    // Stop active conversions and Waveform Generator, keep Reference/LDOs on
     AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT|AFECTRL_WG, bFALSE);
 
-    // 3. Reset FIFO
+    // Reset FIFO configuration
     FIFOCfg_Type fifo_cfg;
     fifo_cfg.FIFOEn = bFALSE;           
     AD5940_FIFOCfg(&fifo_cfg);          
@@ -93,7 +96,7 @@ void AppIMPCleanup(void) {
     fifo_cfg.FIFOThresh = 6;            
     AD5940_FIFOCfg(&fifo_cfg);
     
-    // 4. Clear Interrupts
+    // Clear all interrupt flags
     AD5940_INTCClrFlag(AFEINTSRC_ALLINT);
 }
 
@@ -104,7 +107,7 @@ void AppIMPCalibrateLFO(void) {
     cal_cfg.SystemClkFreq = 16000000.0;
     
     float freq;
-    // Use SDK function to measure LFOSC
+    // Measure LFOSC frequency to calibrate Wakeup Timer
     if(AD5940_LFOSCMeasure(&cal_cfg, &freq) == AD5940ERR_OK) {
         AppIMPCfg.WuptClkFreq = freq;
     }
@@ -128,7 +131,7 @@ int32_t AppIMPCtrl(uint32_t Command, void *pPara)
   {
     case IMPCTRL_START:
     {
-      // Unified Start Logic: Always use Manual Trigger + ENDSEQ Interrupt
+      // Configure interrupts and trigger the first sequence manually
       AD5940_WUPTCtrl(bFALSE); 
       
       AD5940_INTCCfg(AFEINTC_1, AFEINTSRC_ENDSEQ, bTRUE);
@@ -138,7 +141,23 @@ int32_t AppIMPCtrl(uint32_t Command, void *pPara)
       AppIMPCfg.FifoDataCount = 0;
       AppIMPCfg.StopRequired = bFALSE;
       
-      // Trigger first sequence manually
+      // Reset Sweep State for subsequent sweeps
+      if(AppIMPCfg.SweepCfg.SweepEn)
+      {
+        AppIMPCfg.SweepCfg.SweepIndex = 0;
+        AppIMPCfg.SweepCurrFreq = AppIMPCfg.SweepCfg.SweepStart;
+        AppIMPCfg.FreqofData = AppIMPCfg.SweepCfg.SweepStart;
+        
+        // Calculate next frequency immediately so the ISR has the correct 'next' value
+        AD5940_SweepNext(&AppIMPCfg.SweepCfg, &AppIMPCfg.SweepNextFreq);
+        
+        // Reset Hardware WG Frequency to Start Frequency (it was left at Stop Freq)
+        AD5940_WGFreqCtrlS(AppIMPCfg.SweepCurrFreq, AppIMPCfg.SysClkFreq);
+        
+        // Reset SRAM Wait Times for the Start Frequency
+        AppIMPCheckFreq(AppIMPCfg.SweepCurrFreq);
+      }
+
       AD5940_SEQMmrTrig(SEQID_0);
       break;
     }
@@ -189,6 +208,7 @@ float AppIMPGetCurrFreq(void)
     return AppIMPCfg.SinFreq;
 }
 
+/* Generate Initialization Sequence */
 static AD5940Err AppIMPSeqCfgGen(void)
 {
   AD5940Err error = AD5940ERR_OK;
@@ -202,6 +222,7 @@ static AD5940Err AppIMPSeqCfgGen(void)
   AD5940_SEQGenCtrl(bTRUE);
   AD5940_AFECtrlS(AFECTRL_ALL, bFALSE);
 
+  // Configure Reference System (High Power and Low Power Buffers)
   aferef_cfg.HpBandgapEn = bTRUE;
   aferef_cfg.Hp1V1BuffEn = bTRUE;
   aferef_cfg.Hp1V8BuffEn = bTRUE;
@@ -216,6 +237,7 @@ static AD5940Err AppIMPSeqCfgGen(void)
   aferef_cfg.LpRefBoostEn = bFALSE;
   AD5940_REFCfgS(&aferef_cfg);	
   
+  // Configure High Speed Loop (DAC and TIA)
   HsLoopCfg.HsDacCfg.ExcitBufGain = AppIMPCfg.ExcitBufGain;
   HsLoopCfg.HsDacCfg.HsDacGain = AppIMPCfg.HsDacGain;
   HsLoopCfg.HsDacCfg.HsDacUpdateRate = AppIMPCfg.HsDacUpdateRate;
@@ -228,11 +250,13 @@ static AD5940Err AppIMPSeqCfgGen(void)
   HsLoopCfg.HsTiaCfg.HstiaRtiaSel = AppIMPCfg.HstiaRtiaSel;
   HsLoopCfg.HsTiaCfg.ExtRtia = AppIMPCfg.ExtRtia;
 
+  // Configure Switch Matrix
   HsLoopCfg.SWMatCfg.Dswitch = AppIMPCfg.DswitchSel;
   HsLoopCfg.SWMatCfg.Pswitch = AppIMPCfg.PswitchSel;
   HsLoopCfg.SWMatCfg.Nswitch = AppIMPCfg.NswitchSel;
   HsLoopCfg.SWMatCfg.Tswitch = SWT_TRTIA|AppIMPCfg.TswitchSel;
 
+  // Configure Waveform Generator (Sine Wave)
   HsLoopCfg.WgCfg.WgType = WGTYPE_SIN;
   HsLoopCfg.WgCfg.GainCalEn = bTRUE;
   HsLoopCfg.WgCfg.OffsetCalEn = bTRUE;
@@ -256,6 +280,7 @@ static AD5940Err AppIMPSeqCfgGen(void)
   HsLoopCfg.WgCfg.SinCfg.SinPhaseWord = 0;
   AD5940_HSLoopCfgS(&HsLoopCfg);
 
+  // Configure DSP and ADC
   dsp_cfg.ADCBaseCfg.ADCMuxN = ADCMUXN_HSTIA_N;
   dsp_cfg.ADCBaseCfg.ADCMuxP = ADCMUXP_HSTIA_P;
   dsp_cfg.ADCBaseCfg.ADCPga = AppIMPCfg.AdcPgaGain;
@@ -276,6 +301,7 @@ static AD5940Err AppIMPSeqCfgGen(void)
   memset(&dsp_cfg.StatCfg, 0, sizeof(dsp_cfg.StatCfg));
   AD5940_DSPCfgS(&dsp_cfg);
     
+  // Enable Power for AFE blocks
   AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
                 AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
                 AFECTRL_SINC2NOTCH, bTRUE);
@@ -297,6 +323,7 @@ static AD5940Err AppIMPSeqCfgGen(void)
   return AD5940ERR_OK;
 }
 
+/* Generate Measurement Sequence */
 static AD5940Err AppIMPSeqMeasureGen(void)
 {
   AD5940Err error = AD5940ERR_OK;
@@ -306,6 +333,7 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   SWMatrixCfg_Type sw_cfg;
   ClksCalInfo_Type clks_cal;
 
+  // Calculate settling time (WaitClks) based on DFT/Filter settings
   clks_cal.DataType = DATATYPE_DFT;
   clks_cal.DftSrc = AppIMPCfg.DftSrc;
   clks_cal.DataCount = 1L<<(AppIMPCfg.DftNum+2); 
@@ -320,7 +348,7 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   AD5940_SEQGenInsert(SEQ_WAIT(16*250)); 
 
   /* ----------------------------------------------------------------------- */
-  /* Measurement 1: RCAL (Current)                                           */
+  /* Step 1: Measure Current across RCAL (Calibration)                       */
   /* ----------------------------------------------------------------------- */
   sw_cfg.Dswitch = SWD_RCAL0;
   sw_cfg.Pswitch = SWP_RCAL0;
@@ -328,9 +356,10 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   sw_cfg.Tswitch = SWT_RCAL1|SWT_TRTIA;
   AD5940_SWMatrixCfgS(&sw_cfg);
   
-  /* ADC Mux for Current (HSTIA) */
+  // ADC Mux for Current (HSTIA)
   AD5940_ADCMuxCfgS(ADCMUXP_HSTIA_P, ADCMUXN_HSTIA_N);
 
+  // Enable AFE Power and Waveform Generator
   AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
                 AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
                 AFECTRL_SINC2NOTCH, bTRUE);
@@ -338,6 +367,7 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   AD5940_SEQGenInsert(SEQ_WAIT(16*2000)); 
   AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT, bTRUE); 
   
+  // Store address to update wait times later during sweep
   AD5940_SEQGenFetchSeq(NULL, &AppIMPCfg.SeqWaitAddr[0]); 
   AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
   AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
@@ -348,7 +378,7 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   AD5940_AFECtrlS(AFECTRL_WG, bFALSE);
 
   /* ----------------------------------------------------------------------- */
-  /* Measurement 2: Sensor Current (I)                                       */
+  /* Step 2: Measure Sensor Current (I)                                      */
   /* ----------------------------------------------------------------------- */
   sw_cfg.Dswitch = AppIMPCfg.DswitchSel;
   sw_cfg.Pswitch = AppIMPCfg.PswitchSel;
@@ -356,7 +386,7 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   sw_cfg.Tswitch = SWT_TRTIA|AppIMPCfg.TswitchSel;
   AD5940_SWMatrixCfgS(&sw_cfg);
   
-  /* ADC Mux for Current (HSTIA) */
+  // ADC Mux for Current (HSTIA)
   AD5940_ADCMuxCfgS(ADCMUXP_HSTIA_P, ADCMUXN_HSTIA_N);
 
   AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_WG, bTRUE); 
@@ -367,17 +397,16 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
   AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
 
-  // Stop ADC/DFT first, wait 10us, then stop WG
   AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT, bFALSE); 
   AD5940_SEQGenInsert(SEQ_WAIT(16*10)); 
   AD5940_AFECtrlS(AFECTRL_WG, bFALSE);
 
   /* ----------------------------------------------------------------------- */
-  /* Measurement 3: Sensor Voltage (V)                                       */
+  /* Step 3: Measure Sensor Voltage (V)                                      */
   /* ----------------------------------------------------------------------- */
-  /* Switches remain same (Force path active) */
+  // Switches remain same (Force path active)
   
-  /* ADC Mux for Voltage (AIN2/AIN3) */
+  // ADC Mux for Voltage (AIN2/AIN3)
   AD5940_ADCMuxCfgS(ADCMUXP_AIN2, ADCMUXN_AIN3);
 
   AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_WG, bTRUE); 
@@ -388,11 +417,12 @@ static AD5940Err AppIMPSeqMeasureGen(void)
   AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
   AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
 
-  // Stop ADC/DFT first, wait 10us, then stop WG and ADC Power
+  // Stop ADC/DFT, wait 10us, then stop WG and ADC Power
   AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT, bFALSE); 
   AD5940_SEQGenInsert(SEQ_WAIT(16*10)); 
   AD5940_AFECtrlS(AFECTRL_WG|AFECTRL_ADCPWR, bFALSE); 
 
+  // Power down AFE blocks
   AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
                 AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
                 AFECTRL_SINC2NOTCH, bFALSE);
@@ -444,7 +474,7 @@ AD5940Err AppIMPCheckFreq(float freq)
   AD5940_ADCFilterCfgS(&filter_cfg);
   AD5940_DFTCfgS(&dft_cfg);
   
-  // Calculate new WaitClks for the sequence
+  // Recalculate settling times (WaitClks) for the new frequency
   clks_cal.DataType = DATATYPE_DFT;
   clks_cal.DftSrc = freq_params.DftSrc;
   clks_cal.DataCount = 1L<<(freq_params.DftNum+2); 
@@ -482,7 +512,7 @@ int32_t AppIMPInit(uint32_t *pBuffer, uint32_t BufferSize)
 
   if(AD5940_WakeUp(10) > 10) return AD5940ERR_WAKEUP;
 
-  // CRITICAL: Stop WUPT and Sequencer before reconfiguration
+  // Stop timers and sequencer before reconfiguration
   AD5940_WUPTCtrl(bFALSE);
   AD5940_SEQCtrlS(bFALSE);
 
@@ -526,7 +556,7 @@ int32_t AppIMPInit(uint32_t *pBuffer, uint32_t BufferSize)
   
   AD5940_INTCCfg(AFEINTC_1, AFEINTSRC_ENDSEQ, bTRUE);
   
-  // Safety timeout for Init Sequence
+  // Wait for initialization sequence to complete
   int timeout = 100000;
   while(AD5940_INTCTestFlag(AFEINTC_1, AFEINTSRC_ENDSEQ) == bFALSE) {
       if(--timeout <= 0) {
@@ -614,6 +644,7 @@ int32_t AppIMPDataProcess(int32_t * const pData, uint32_t *pDataCount)
     MagV = sqrt((float)pDftV->Real*pDftV->Real + (float)pDftV->Image*pDftV->Image);
     PhaseV = atan2(-pDftV->Image, pDftV->Real);
 
+    // Calculate Impedance: Z = (V / I) * Rtia
     if(MagI > 1e-9) 
         ZMag = (MagV / MagI) * AppIMPCfg.RtiaVal;
     else
@@ -705,9 +736,7 @@ int32_t AppIMPISR(void *pBuff, uint32_t *pCount)
           AD5940_SleepKeyCtrlS(SLPKEY_UNLOCK); 
           AppIMPDataProcess((int32_t*)pBuff, &FifoCnt); 
           
-          // DUMMY POINT FILTERING
+          // Discard extra data points if they exceed the requested count
-          // If we are in sweep mode and have exceeded the user's requested count,
-          // discard this data packet so the host doesn't see the artifact.
           if (AppIMPCfg.SweepCfg.SweepEn && AppIMPCfg.RealDataCount > 0) {
               if (AppIMPCfg.FifoDataCount > AppIMPCfg.RealDataCount) {
                   *pCount = 0; // Discard

host/src/MainWindow.cpp

@@ -82,7 +82,6 @@ void MainWindow::setupUi() {
     nyquistGraph = new GraphWidget(this);
     nyquistGraph->configureNyquistPlot();
 
-    // Raw Data is now Default (Index 0)
     tabWidget->addTab(rawGraph, "Raw Data");
     tabWidget->addTab(nyquistGraph, "Nyquist Plot");
 
@@ -329,6 +328,7 @@ void MainWindow::parseData(const QString &data) {
     }
 }
 
+
 void MainWindow::computeHilbert() {
     int n = sweepReals.size();
     if (n == 0) return;
@@ -360,7 +360,7 @@ void MainWindow::computeHilbert() {
     // 4. IFFT
     ifft(signal);
 
-    // 5. Extract Imaginary Part (Hilbert Transform)
+    // 5. Extract Imaginary Part (Hilbert Transform) to represent the analytical.
     QVector<double> hilbertImag;
     for (int i = 0; i < n; i++) {
         hilbertImag.append(signal[i].imag());

host/src/main.cpp

@@ -1,4 +1,4 @@
-// File: aluf/src/main.cpp
+// File: host/src/main.cpp
 #include <QApplication>
 #include "MainWindow.h"