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EVAL-AD5940ELCZ Changing SINC3 & SINC2 Filters During Time-of-Flight

Hello  ,

I am using the code provided from https://github.com/analogdevicesinc/ad5940-examples to program the EVAL-AD5940ELCZ for electrochemical impedance spectroscopy.

I need to sweep frequencies from 0.1Hz to 10kHz. With default parameters, there was noise in the impedance measurement at low frequencies. After engaging the SINC2 filter, there was a reduction in noise in the impedance measurement at low frequencies; however, the quality of the impedance measurement at high frequencies decreased ( RE: EIS 2-wire measurements using EVAL-AD5940ELCZ ).

I would like to engage the SINC2 filter at low frequencies and disengage the SINC2 filter at high frequencies; note that I would like to do this at time-of-flight. For example, engage the SINC2 filter until the sweep frequency is 100Hz, then disengage the SINC2 filter.

In a previous discussion, it was mentioned that the AppIMPRegModify() function is a good place to update the AFE during time-of-flight ( AD5940 ELCZ - using SINC2 data for the DFT not working ).

Following this discussion, I attempted to disengage the SINC2 filter in the AppIMPRegModify() function by adding the following to it:

float freq = AppIMPGetCurrFreq();
if(SWITCHING_FREQ < freq) {
    AppIMPCfg_Type *pImpedanceCfg;
    AppIMPGetCfg(&pImpedanceCfg);
    pImpedanceCfg->DftSrc = DFTSRC_SINC3; // Reset DftSrc to SINC3, disengaging SINC2 and increasing the oversampling rate
}

However, I did not observe an increase in the oversampling rate. I am left with the following questions:

1. What do I need to write in the AppIMPRegModify() function? Is the above code sufficient?

2. Do I need to call a function to reinitialize the AFE?

Thank you for your assistance.

  • Hi,

    You may modify the AD5940_ECSns_EIS code as below:

    Impedance.c :-

    /*!
     *****************************************************************************
     @file:    Impedance.c
     @author:  Neo Xu
     @brief:   Electrochemical impedance spectroscopy based on example AD5940_Impedance
     -----------------------------------------------------------------------------
    
    Copyright (c) 2017-2019 Analog Devices, Inc. All Rights Reserved.
    
    This software is proprietary to Analog Devices, Inc. and its licensors.
    By using this software you agree to the terms of the associated
    Analog Devices Software License Agreement.
     
    *****************************************************************************/
    #include "AD5940.H"
    #include <stdio.h>
    #include "string.h"
    #include "math.h"
    #include "Impedance.h"
    
    /* Default LPDAC resolution(2.5V internal reference). */
    #define DAC12BITVOLT_1LSB   (2200.0f/4095)  //mV
    #define DAC6BITVOLT_1LSB    (DAC12BITVOLT_1LSB*64)  //mV
    
    /* 
      Application configuration structure. Specified by user from template.
      The variables are usable in this whole application.
      It includes basic configuration for sequencer generator and application related parameters
    */
    AppIMPCfg_Type AppIMPCfg = 
    {
      .bParaChanged = bFALSE,
      .SeqStartAddr = 0,
      .MaxSeqLen = 0,
      
      .SeqStartAddrCal = 0,
      .MaxSeqLenCal = 0,
    
      .ImpODR = 20.0,           /* 20.0 Hz*/
      .NumOfData = -1,
      .SysClkFreq = 16000000.0,
      .WuptClkFreq = 32000.0,
      .AdcClkFreq = 16000000.0,
      .RcalVal = 10000.0,
    
      .DswitchSel = SWD_CE0,
      .PswitchSel = SWP_CE0,
      .NswitchSel = SWN_AIN1,
      .TswitchSel = SWT_AIN1,
    
      .PwrMod = AFEPWR_LP,
    
      .LptiaRtiaSel = LPTIARTIA_4K, /* COnfigure RTIA */
      .LpTiaRf = LPTIARF_1M,        /* Configure LPF resistor */
      .LpTiaRl = LPTIARLOAD_100R,
    	
      .HstiaRtiaSel = HSTIARTIA_1K,
      .ExcitBufGain = EXCITBUFGAIN_0P25,
      .HsDacGain = HSDACGAIN_0P2,
      .HsDacUpdateRate = 0x1B,
      .DacVoltPP = 300.0,
      .BiasVolt = -0.0f,
    
      .SinFreq = 100000.0, /* 1000Hz */
    
      .DftNum = DFTNUM_16384,
      .DftSrc = DFTSRC_SINC3,
      .HanWinEn = bTRUE,
    
      .AdcPgaGain = ADCPGA_1,
      .ADCSinc3Osr = ADCSINC3OSR_2,
      .ADCSinc2Osr = ADCSINC2OSR_22,
    
      .ADCAvgNum = ADCAVGNUM_16,
    
      .SweepCfg.SweepEn = bTRUE,
      .SweepCfg.SweepStart = 1000,
      .SweepCfg.SweepStop = 100000.0,
      .SweepCfg.SweepPoints = 101,
      .SweepCfg.SweepLog = bFALSE,
      .SweepCfg.SweepIndex = 0,
    
      .FifoThresh = 4,
      .IMPInited = bFALSE,
      .StopRequired = bFALSE,
    };
    
    /* Depending on frequency of Sin wave set optimum filter settings */
    AD5940Err AppIMPCheckFreq(float freq)
    {
      ADCFilterCfg_Type filter_cfg;
      DFTCfg_Type dft_cfg;
      HSDACCfg_Type hsdac_cfg;
      uint32_t WaitClks;
      ClksCalInfo_Type clks_cal;
      FreqParams_Type freq_params;
      uint32_t SeqCmdBuff[32];
      uint32_t SRAMAddr = 0;;
      /* Step 1: Check Frequency */
      freq_params = AD5940_GetFreqParameters(freq);
      
           if(freq < 0.51)
    	{
                /* Update HSDAC update rate */
        hsdac_cfg.ExcitBufGain =EXCITBUFGAIN_2;// AppIMPCfg.ExcitBufGain;
        hsdac_cfg.HsDacGain = HSDACGAIN_1;//AppIMPCfg.HsDacGain;
         hsdac_cfg.HsDacUpdateRate = 0x1B;
        AD5940_HSDacCfgS(&hsdac_cfg);
        AD5940_HSRTIACfgS(HSTIARTIA_40K);
        
        /*Update ADC rate */
        filter_cfg.ADCRate = ADCRATE_800KHZ;
        AppIMPCfg.AdcClkFreq = 16e6;
        
        /* Change clock to 16MHz oscillator */
        AD5940_HPModeEn(bFALSE);
    	}
            else if(freq < 5 )
    	{
           /* Update HSDAC update rate */
        hsdac_cfg.ExcitBufGain =EXCITBUFGAIN_2;// AppIMPCfg.ExcitBufGain;
        hsdac_cfg.HsDacGain = HSDACGAIN_1;//AppIMPCfg.HsDacGain;
        hsdac_cfg.HsDacUpdateRate = 0x1B;
        AD5940_HSDacCfgS(&hsdac_cfg);
        AD5940_HSRTIACfgS(HSTIARTIA_40K);
        
        /*Update ADC rate */
        filter_cfg.ADCRate = ADCRATE_800KHZ;
        AppIMPCfg.AdcClkFreq = 16e6;
        
        /* Change clock to 16MHz oscillator */
        AD5940_HPModeEn(bFALSE);
        
    	}else if(freq < 450)
    	{
           /* Update HSDAC update rate */
        hsdac_cfg.ExcitBufGain =AppIMPCfg.ExcitBufGain;
        hsdac_cfg.HsDacGain = AppIMPCfg.HsDacGain;  
        
         hsdac_cfg.HsDacUpdateRate = 0x1B;
        AD5940_HSDacCfgS(&hsdac_cfg);
        AD5940_HSRTIACfgS(HSTIARTIA_5K);
        
        /*Update ADC rate */
        filter_cfg.ADCRate = ADCRATE_800KHZ;
        AppIMPCfg.AdcClkFreq = 16e6;
        
        /* Change clock to 16MHz oscillator */
        AD5940_HPModeEn(bFALSE);
    	}
           else if(freq<80000)
           {
               /* Update HSDAC update rate */
        hsdac_cfg.ExcitBufGain =AppIMPCfg.ExcitBufGain;
        hsdac_cfg.HsDacGain = AppIMPCfg.HsDacGain;
        hsdac_cfg.HsDacUpdateRate = 0x1B;
        AD5940_HSDacCfgS(&hsdac_cfg);
        AD5940_HSRTIACfgS(HSTIARTIA_5K);
        
        /*Update ADC rate */
        filter_cfg.ADCRate = ADCRATE_800KHZ;
        AppIMPCfg.AdcClkFreq = 16e6;
        
        /* Change clock to 16MHz oscillator */
        AD5940_HPModeEn(bFALSE);
           }
            /* High power mode */
    	if(freq >= 80000)
    	{
    		  /* Update HSDAC update rate */
        hsdac_cfg.ExcitBufGain =AppIMPCfg.ExcitBufGain;
        hsdac_cfg.HsDacGain = AppIMPCfg.HsDacGain;
        hsdac_cfg.HsDacUpdateRate = 0x07;
        AD5940_HSDacCfgS(&hsdac_cfg);
        AD5940_HSRTIACfgS(HSTIARTIA_5K);
        
        /*Update ADC rate */
        filter_cfg.ADCRate = ADCRATE_1P6MHZ;
        AppIMPCfg.AdcClkFreq = 32e6;
        
        /* Change clock to 32MHz oscillator */
        AD5940_HPModeEn(bTRUE);
    	}
      
      /* Step 2: Adjust ADCFILTERCON and DFTCON to set optimumn SINC3, SINC2 and DFTNUM settings  */
      filter_cfg.ADCAvgNum = ADCAVGNUM_16;  /* Don't care because it's disabled */ 
      filter_cfg.ADCSinc2Osr = freq_params.ADCSinc2Osr;
      filter_cfg.ADCSinc3Osr = freq_params.ADCSinc3Osr;
      filter_cfg.BpSinc3 = bFALSE;
      filter_cfg.BpNotch = bTRUE;
      filter_cfg.Sinc2NotchEnable = bTRUE;
      dft_cfg.DftNum = freq_params.DftNum;
      dft_cfg.DftSrc = freq_params.DftSrc;
      dft_cfg.HanWinEn = AppIMPCfg.HanWinEn;
      AD5940_ADCFilterCfgS(&filter_cfg);
      AD5940_DFTCfgS(&dft_cfg);
      
      /* Step 3: Calculate clocks needed to get result to FIFO and update sequencer wait command */
      clks_cal.DataType = DATATYPE_DFT;
      clks_cal.DftSrc = freq_params.DftSrc;
      clks_cal.DataCount = 1L<<(freq_params.DftNum+2); /* 2^(DFTNUMBER+2) */
      clks_cal.ADCSinc2Osr = freq_params.ADCSinc2Osr;
      clks_cal.ADCSinc3Osr = freq_params.ADCSinc3Osr;
      clks_cal.ADCAvgNum = 0;
      clks_cal.RatioSys2AdcClk = AppIMPCfg.SysClkFreq/AppIMPCfg.AdcClkFreq;
      AD5940_ClksCalculate(&clks_cal, &WaitClks);		
    	
    	
    	  SRAMAddr = AppIMPCfg.MeasureSeqInfo.SeqRamAddr + AppIMPCfg.SeqWaitAddr[0];
    	   
               SeqCmdBuff[0] =SEQ_WAIT(WaitClks/2);
               SeqCmdBuff[1] =SEQ_WAIT(WaitClks/2);
          
    		AD5940_SEQCmdWrite(SRAMAddr, SeqCmdBuff, 2);
    		
    		SRAMAddr = AppIMPCfg.MeasureSeqInfo.SeqRamAddr + AppIMPCfg.SeqWaitAddr[1];
    		  
               SeqCmdBuff[0] =SEQ_WAIT(WaitClks/2);
               SeqCmdBuff[1] =SEQ_WAIT(WaitClks/2);
    
    		AD5940_SEQCmdWrite(SRAMAddr, SeqCmdBuff, 2);
                    
                    SRAMAddr = AppIMPCfg.MeasureSeqInfo.SeqRamAddr + AppIMPCfg.SeqWaitAddr[2];
    		  
               SeqCmdBuff[0] =SEQ_WAIT(WaitClks/2);
               SeqCmdBuff[1] =SEQ_WAIT(WaitClks/2);
    
    		AD5940_SEQCmdWrite(SRAMAddr, SeqCmdBuff, 2);
    
     
      return AD5940ERR_OK;
    }
    /**
       This function is provided for upper controllers that want to change 
       application parameters specially for user defined parameters.
    */
    int32_t AppIMPGetCfg(void *pCfg)
    {
      if(pCfg)
      {
        *(AppIMPCfg_Type**)pCfg = &AppIMPCfg;
        return AD5940ERR_OK;
      }
      return AD5940ERR_PARA;
    }
    
    int32_t AppIMPCtrl(uint32_t Command, void *pPara)
    {
      
      switch (Command)
      {
        case IMPCTRL_START:
        {
          WUPTCfg_Type wupt_cfg;
    
          if(AD5940_WakeUp(10) > 10)  /* Wakeup AFE by read register, read 10 times at most */
            return AD5940ERR_WAKEUP;  /* Wakeup Failed */
          if(AppIMPCfg.IMPInited == bFALSE)
            return AD5940ERR_APPERROR;
          /* Start it */
          wupt_cfg.WuptEn = bTRUE;
          wupt_cfg.WuptEndSeq = WUPTENDSEQ_A;
          wupt_cfg.WuptOrder[0] = SEQID_0;
          wupt_cfg.SeqxSleepTime[SEQID_0] = 4;
          wupt_cfg.SeqxWakeupTime[SEQID_0] = (uint32_t)(AppIMPCfg.WuptClkFreq/AppIMPCfg.ImpODR)-4;
          AD5940_WUPTCfg(&wupt_cfg);
          
          AppIMPCfg.FifoDataCount = 0;  /* restart */
          break;
        }
        case IMPCTRL_STOPNOW:
        {
          if(AD5940_WakeUp(10) > 10)  /* Wakeup AFE by read register, read 10 times at most */
            return AD5940ERR_WAKEUP;  /* Wakeup Failed */
          /* Start Wupt right now */
          AD5940_WUPTCtrl(bFALSE);
          AD5940_WUPTCtrl(bFALSE);
          break;
        }
        case IMPCTRL_STOPSYNC:
        {
          AppIMPCfg.StopRequired = bTRUE;
          break;
        }
        case IMPCTRL_GETFREQ:
          {
            if(pPara == 0)
              return AD5940ERR_PARA;
            if(AppIMPCfg.SweepCfg.SweepEn == bTRUE)
              *(float*)pPara = AppIMPCfg.FreqofData;
            else
              *(float*)pPara = AppIMPCfg.SinFreq;
          }
        break;
        case IMPCTRL_SHUTDOWN:
        {
          AppIMPCtrl(IMPCTRL_STOPNOW, 0);  /* Stop the measurement if it's running. */
          /* Turn off LPloop related blocks which are not controlled automatically by hibernate operation */
          AFERefCfg_Type aferef_cfg;
          LPLoopCfg_Type lploop_cfg;
          memset(&aferef_cfg, 0, sizeof(aferef_cfg));
          AD5940_REFCfgS(&aferef_cfg);
          memset(&lploop_cfg, 0, sizeof(lploop_cfg));
          AD5940_LPLoopCfgS(&lploop_cfg);
          AD5940_EnterSleepS();  /* Enter Hibernate */
        }
        break;
        default:
        break;
      }
      return AD5940ERR_OK;
    }
    
    /* generated code snnipet */
    float AppIMPGetCurrFreq(void)
    {
      if(AppIMPCfg.SweepCfg.SweepEn == bTRUE)
        return AppIMPCfg.FreqofData;
      else
        return AppIMPCfg.SinFreq;
    }
    
    /* Application initialization */
    static AD5940Err AppIMPSeqCfgGen(void)
    {
      AD5940Err error = AD5940ERR_OK;
      const uint32_t *pSeqCmd;
      uint32_t SeqLen;
      AFERefCfg_Type aferef_cfg;
      HSLoopCfg_Type HsLoopCfg;
    	LPLoopCfg_Type lploop_cfg;
      DSPCfg_Type dsp_cfg;
      float sin_freq;
    
      /* Start sequence generator here */
      AD5940_SEQGenCtrl(bTRUE);
      
      AD5940_AFECtrlS(AFECTRL_ALL, bFALSE);  /* Init all to disable state */
    
      aferef_cfg.HpBandgapEn = bTRUE;
      aferef_cfg.Hp1V1BuffEn = bTRUE;
      aferef_cfg.Hp1V8BuffEn = bTRUE;
      aferef_cfg.Disc1V1Cap = bFALSE;
      aferef_cfg.Disc1V8Cap = bFALSE;
      aferef_cfg.Hp1V8ThemBuff = bFALSE;
      aferef_cfg.Hp1V8Ilimit = bFALSE;
      aferef_cfg.Lp1V1BuffEn = bFALSE;
      aferef_cfg.Lp1V8BuffEn = bFALSE;
      aferef_cfg.LpBandgapEn = bTRUE;
      aferef_cfg.LpRefBufEn = bTRUE;
      aferef_cfg.LpRefBoostEn = bFALSE;
      AD5940_REFCfgS(&aferef_cfg);	
    	
    	lploop_cfg.LpDacCfg.LpDacSrc = LPDACSRC_MMR;
      lploop_cfg.LpDacCfg.LpDacSW = LPDACSW_VBIAS2LPPA|LPDACSW_VBIAS2PIN|LPDACSW_VZERO2LPTIA|LPDACSW_VZERO2PIN;
      lploop_cfg.LpDacCfg.LpDacVzeroMux = LPDACVZERO_6BIT;
      lploop_cfg.LpDacCfg.LpDacVbiasMux = LPDACVBIAS_12BIT;
      lploop_cfg.LpDacCfg.LpDacRef = LPDACREF_2P5;
      lploop_cfg.LpDacCfg.DataRst = bFALSE;
      lploop_cfg.LpDacCfg.PowerEn = bTRUE;
      lploop_cfg.LpDacCfg.DacData6Bit = (uint32_t)((AppIMPCfg.Vzero-200)/DAC6BITVOLT_1LSB);
    	lploop_cfg.LpDacCfg.DacData12Bit =(int32_t)((AppIMPCfg.BiasVolt)/DAC12BITVOLT_1LSB) + lploop_cfg.LpDacCfg.DacData6Bit*64;
    	if(lploop_cfg.LpDacCfg.DacData12Bit>lploop_cfg.LpDacCfg.DacData6Bit*64)
    		lploop_cfg.LpDacCfg.DacData12Bit--;
      lploop_cfg.LpAmpCfg.LpAmpPwrMod = LPAMPPWR_NORM;
      lploop_cfg.LpAmpCfg.LpPaPwrEn = bTRUE;
      lploop_cfg.LpAmpCfg.LpTiaPwrEn = bTRUE;
      lploop_cfg.LpAmpCfg.LpTiaRf = AppIMPCfg.LpTiaRf;
      lploop_cfg.LpAmpCfg.LpTiaRload = AppIMPCfg.LpTiaRl;
      lploop_cfg.LpAmpCfg.LpTiaRtia = AppIMPCfg.LptiaRtiaSel;
      lploop_cfg.LpAmpCfg.LpTiaSW = LPTIASW(5)|LPTIASW(2)|LPTIASW(4)|LPTIASW(12)|LPTIASW(13); 
      
      AD5940_LPLoopCfgS(&lploop_cfg);
    	
      HsLoopCfg.HsDacCfg.ExcitBufGain = AppIMPCfg.ExcitBufGain;
      HsLoopCfg.HsDacCfg.HsDacGain = AppIMPCfg.HsDacGain;
      HsLoopCfg.HsDacCfg.HsDacUpdateRate = AppIMPCfg.HsDacUpdateRate;
    
      HsLoopCfg.HsTiaCfg.DiodeClose = bFALSE;
      HsLoopCfg.HsTiaCfg.HstiaBias = HSTIABIAS_1P1;
      HsLoopCfg.HsTiaCfg.HstiaCtia = 31; /* 31pF + 2pF */
      HsLoopCfg.HsTiaCfg.HstiaDeRload = HSTIADERLOAD_OPEN;
      HsLoopCfg.HsTiaCfg.HstiaDeRtia = HSTIADERTIA_OPEN;
      HsLoopCfg.HsTiaCfg.HstiaRtiaSel = AppIMPCfg.HstiaRtiaSel;
    
      HsLoopCfg.SWMatCfg.Dswitch = AppIMPCfg.DswitchSel;
      HsLoopCfg.SWMatCfg.Pswitch = AppIMPCfg.PswitchSel;
      HsLoopCfg.SWMatCfg.Nswitch = AppIMPCfg.NswitchSel;
      HsLoopCfg.SWMatCfg.Tswitch = SWT_TRTIA|AppIMPCfg.TswitchSel;
    
      HsLoopCfg.WgCfg.WgType = WGTYPE_SIN;
      HsLoopCfg.WgCfg.GainCalEn = bTRUE;
      HsLoopCfg.WgCfg.OffsetCalEn = bTRUE;
      if(AppIMPCfg.SweepCfg.SweepEn == bTRUE)
      {
        AppIMPCfg.FreqofData = AppIMPCfg.SweepCfg.SweepStart;
        AppIMPCfg.SweepCurrFreq = AppIMPCfg.SweepCfg.SweepStart;
        AD5940_SweepNext(&AppIMPCfg.SweepCfg, &AppIMPCfg.SweepNextFreq);
        sin_freq = AppIMPCfg.SweepCurrFreq;
      }
      else
      {
        sin_freq = AppIMPCfg.SinFreq;
        AppIMPCfg.FreqofData = sin_freq;
      }
      HsLoopCfg.WgCfg.SinCfg.SinFreqWord = AD5940_WGFreqWordCal(sin_freq, AppIMPCfg.SysClkFreq);
    	HsLoopCfg.WgCfg.SinCfg.SinAmplitudeWord = (uint32_t)(AppIMPCfg.DacVoltPP/800.0f*2047 + 0.5f);
      HsLoopCfg.WgCfg.SinCfg.SinOffsetWord = 0;
      HsLoopCfg.WgCfg.SinCfg.SinPhaseWord = 0;
      AD5940_HSLoopCfgS(&HsLoopCfg);
    
      dsp_cfg.ADCBaseCfg.ADCMuxN = ADCMUXN_HSTIA_N;
      dsp_cfg.ADCBaseCfg.ADCMuxP = ADCMUXP_HSTIA_P;
      dsp_cfg.ADCBaseCfg.ADCPga = AppIMPCfg.AdcPgaGain;
      
      memset(&dsp_cfg.ADCDigCompCfg, 0, sizeof(dsp_cfg.ADCDigCompCfg));
      
      dsp_cfg.ADCFilterCfg.ADCAvgNum = AppIMPCfg.ADCAvgNum;
      dsp_cfg.ADCFilterCfg.ADCRate = ADCRATE_800KHZ;	/* Tell filter block clock rate of ADC*/
      dsp_cfg.ADCFilterCfg.ADCSinc2Osr = AppIMPCfg.ADCSinc2Osr;
      dsp_cfg.ADCFilterCfg.ADCSinc3Osr = AppIMPCfg.ADCSinc3Osr;
      dsp_cfg.ADCFilterCfg.BpNotch = bTRUE;
      dsp_cfg.ADCFilterCfg.BpSinc3 = bFALSE;
      dsp_cfg.ADCFilterCfg.Sinc2NotchEnable = bTRUE;
      dsp_cfg.DftCfg.DftNum = AppIMPCfg.DftNum;
      dsp_cfg.DftCfg.DftSrc = AppIMPCfg.DftSrc;
      dsp_cfg.DftCfg.HanWinEn = AppIMPCfg.HanWinEn;
      
      memset(&dsp_cfg.StatCfg, 0, sizeof(dsp_cfg.StatCfg));
      AD5940_DSPCfgS(&dsp_cfg);
        
      /* Enable all of them. They are automatically turned off during hibernate mode to save power */
      if(AppIMPCfg.BiasVolt == 0.0f)
        AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
                    AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
                    AFECTRL_SINC2NOTCH, bTRUE);
      else
        AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
                    AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
                    AFECTRL_SINC2NOTCH|AFECTRL_DCBUFPWR, bTRUE);
        /* Sequence end. */
      AD5940_SEQGenInsert(SEQ_STOP()); /* Add one extra command to disable sequencer for initialization sequence because we only want it to run one time. */
    
      /* Stop here */
      error = AD5940_SEQGenFetchSeq(&pSeqCmd, &SeqLen);
      AD5940_SEQGenCtrl(bFALSE); /* Stop sequencer generator */
      if(error == AD5940ERR_OK)
      {
        AppIMPCfg.InitSeqInfo.SeqId = SEQID_1;
        AppIMPCfg.InitSeqInfo.SeqRamAddr = AppIMPCfg.SeqStartAddr;
        AppIMPCfg.InitSeqInfo.pSeqCmd = pSeqCmd;
        AppIMPCfg.InitSeqInfo.SeqLen = SeqLen;
        /* Write command to SRAM */
        AD5940_SEQCmdWrite(AppIMPCfg.InitSeqInfo.SeqRamAddr, pSeqCmd, SeqLen);
      }
      else
        return error; /* Error */
      return AD5940ERR_OK;
    }
    
    
    static AD5940Err AppIMPSeqMeasureGen(void)
    {
      AD5940Err error = AD5940ERR_OK;
      const uint32_t *pSeqCmd;
      uint32_t SeqLen;
      
      uint32_t WaitClks;
      SWMatrixCfg_Type sw_cfg;
      ClksCalInfo_Type clks_cal;
      LPAmpCfg_Type LpAmpCfg;
    	
      /* Calculate number of clocks to get data to FIFO */
      clks_cal.DataType = DATATYPE_DFT;
      clks_cal.DftSrc = AppIMPCfg.DftSrc;
      clks_cal.DataCount = 1L<<(AppIMPCfg.DftNum+2); /* 2^(DFTNUMBER+2) */
      clks_cal.ADCSinc2Osr = AppIMPCfg.ADCSinc2Osr;
      clks_cal.ADCSinc3Osr = AppIMPCfg.ADCSinc3Osr;
      clks_cal.ADCAvgNum = AppIMPCfg.ADCAvgNum;
      clks_cal.RatioSys2AdcClk = AppIMPCfg.SysClkFreq/AppIMPCfg.AdcClkFreq;
      AD5940_ClksCalculate(&clks_cal, &WaitClks);
      
      /* Start Sequence Generator */
      AD5940_SEQGenCtrl(bTRUE);
      AD5940_SEQGpioCtrlS(AGPIO_Pin2); /* Set GPIO1, clear others that under control */
      AD5940_SEQGenInsert(SEQ_WAIT(16*250));  /* @todo wait 250us? */
    
      /* Disconnect SE0 from LPTIA*/
    	LpAmpCfg.LpAmpPwrMod = LPAMPPWR_NORM;
      LpAmpCfg.LpPaPwrEn = bTRUE;
      LpAmpCfg.LpTiaPwrEn = bTRUE;
      LpAmpCfg.LpTiaRf = AppIMPCfg.LpTiaRf;
      LpAmpCfg.LpTiaRload = AppIMPCfg.LpTiaRl;
      LpAmpCfg.LpTiaRtia = LPTIARTIA_OPEN; /* Disconnect Rtia to avoid RC filter discharge */
      LpAmpCfg.LpTiaSW = LPTIASW(7)|LPTIASW(8)|LPTIASW(12)|LPTIASW(13); 
    	AD5940_LPAMPCfgS(&LpAmpCfg);
      /* Sensor + Rload Measurement */
      sw_cfg.Dswitch = AppIMPCfg.DswitchSel;
      sw_cfg.Pswitch = AppIMPCfg.PswitchSel;
      sw_cfg.Nswitch = AppIMPCfg.NswitchSel;
      sw_cfg.Tswitch = SWT_TRTIA|AppIMPCfg.TswitchSel;
      AD5940_SWMatrixCfgS(&sw_cfg);
      
      AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
                    AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
                    AFECTRL_SINC2NOTCH, bTRUE);
      
    																 
      AD5940_AFECtrlS(AFECTRL_ADCPWR|AFECTRL_SINC2NOTCH, bTRUE);  /* Enable Waveform generator */
      //delay for signal settling DFT_WAIT
      AD5940_SEQGenInsert(SEQ_WAIT(16*10));
      AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT, bTRUE);  /* Start ADC convert and DFT */
       AD5940_SEQGenFetchSeq(NULL, &AppIMPCfg.SeqWaitAddr[0]); /* Record the start address of the next command. */
    
      AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
       AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
      //wait for first data ready
      AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
        AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
          AFECTRL_SINC2NOTCH|AFECTRL_DFT|AFECTRL_ADCCNV, bFALSE);
      
      /* RLOAD Measurement */
      sw_cfg.Dswitch = SWD_SE0;
      sw_cfg.Pswitch = SWP_SE0;
      sw_cfg.Nswitch = SWN_SE0LOAD;
      sw_cfg.Tswitch = SWT_SE0LOAD|SWT_TRTIA;
      AD5940_SWMatrixCfgS(&sw_cfg);
      AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
        AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|AFECTRL_SINC2NOTCH, bTRUE);
      AD5940_SEQGenInsert(SEQ_WAIT(16*10));  //delay for signal settling DFT_WAIT
      AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT, bTRUE);  /* Start ADC convert and DFT */
      AD5940_SEQGenFetchSeq(NULL, &AppIMPCfg.SeqWaitAddr[1]); /* Record the start address of the next command. */
    
      AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
       AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
      AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
        AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
          AFECTRL_SINC2NOTCH|AFECTRL_ADCCNV, bFALSE);
      
      /* RCAL Measurement */
      sw_cfg.Dswitch = SWD_RCAL0;
      sw_cfg.Pswitch = SWP_RCAL0;
      sw_cfg.Nswitch = SWN_RCAL1;
      sw_cfg.Tswitch = SWT_RCAL1|SWT_TRTIA;
      AD5940_SWMatrixCfgS(&sw_cfg);
    	/* Reconnect LP loop */
    	LpAmpCfg.LpTiaRtia = AppIMPCfg.LptiaRtiaSel; /* Disconnect Rtia to avoid RC filter discharge */
      LpAmpCfg.LpTiaSW = LPTIASW(5)|LPTIASW(2)|LPTIASW(4)|LPTIASW(12)|LPTIASW(13); 
    	AD5940_LPAMPCfgS(&LpAmpCfg);
    	
      AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
        AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|AFECTRL_SINC2NOTCH, bTRUE);
      AD5940_SEQGenInsert(SEQ_WAIT(16*10));  //delay for signal settling DFT_WAIT
      AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT/*|AFECTRL_SINC2NOTCH*/, bTRUE);  /* Start ADC convert and DFT */
     AD5940_SEQGenFetchSeq(NULL, &AppIMPCfg.SeqWaitAddr[2]); /* Record the start address of the next command. */
    
      AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
       AD5940_SEQGenInsert(SEQ_WAIT(WaitClks/2));
      AD5940_AFECtrlS(AFECTRL_ADCCNV|AFECTRL_DFT|AFECTRL_WG|AFECTRL_ADCPWR, bFALSE);  /* Stop ADC convert and DFT */
      AD5940_AFECtrlS(AFECTRL_HSTIAPWR|AFECTRL_INAMPPWR|AFECTRL_EXTBUFPWR|\
        AFECTRL_WG|AFECTRL_DACREFPWR|AFECTRL_HSDACPWR|\
          AFECTRL_SINC2NOTCH, bFALSE);
      AD5940_SEQGpioCtrlS(0); /* Clr GPIO1 */
      
      sw_cfg.Dswitch = SWD_OPEN;
      sw_cfg.Pswitch = SWP_OPEN;
      sw_cfg.Nswitch = SWN_OPEN;
      sw_cfg.Tswitch = SWT_OPEN;
      AD5940_SWMatrixCfgS(&sw_cfg);
      
      //AD5940_EnterSleepS();/* Goto hibernate */
      
      /* Sequence end. */
      error = AD5940_SEQGenFetchSeq(&pSeqCmd, &SeqLen);
      AD5940_SEQGenCtrl(bFALSE); /* Stop sequencer generator */
    
      if(error == AD5940ERR_OK)
      {
        AppIMPCfg.MeasureSeqInfo.SeqId = SEQID_0;
        AppIMPCfg.MeasureSeqInfo.SeqRamAddr = AppIMPCfg.InitSeqInfo.SeqRamAddr + AppIMPCfg.InitSeqInfo.SeqLen ;
        AppIMPCfg.MeasureSeqInfo.pSeqCmd = pSeqCmd;
        AppIMPCfg.MeasureSeqInfo.SeqLen = SeqLen;
        /* Write command to SRAM */
        AD5940_SEQCmdWrite(AppIMPCfg.MeasureSeqInfo.SeqRamAddr, pSeqCmd, SeqLen);
      }
      else
        return error; /* Error */
      return AD5940ERR_OK;
    }
    
    
    /* This function provide application initialize. It can also enable Wupt that will automatically trigger sequence. Or it can configure  */
    int32_t AppIMPInit(uint32_t *pBuffer, uint32_t BufferSize)
    {
      AD5940Err error = AD5940ERR_OK;  
      SEQCfg_Type seq_cfg;
      FIFOCfg_Type fifo_cfg;
    
      if(AD5940_WakeUp(10) > 10)  /* Wakeup AFE by read register, read 10 times at most */
        return AD5940ERR_WAKEUP;  /* Wakeup Failed */
    
      /* Configure sequencer and stop it */
      seq_cfg.SeqMemSize = SEQMEMSIZE_2KB;  /* 2kB SRAM is used for sequencer, others for data FIFO */
      seq_cfg.SeqBreakEn = bFALSE;
      seq_cfg.SeqIgnoreEn = bTRUE;
      seq_cfg.SeqCntCRCClr = bTRUE;
      seq_cfg.SeqEnable = bFALSE;
      seq_cfg.SeqWrTimer = 0;
      AD5940_SEQCfg(&seq_cfg);
      
      /* Reconfigure FIFO */
      AD5940_FIFOCtrlS(FIFOSRC_DFT, bFALSE);									/* Disable FIFO firstly */
      fifo_cfg.FIFOEn = bTRUE;
      fifo_cfg.FIFOMode = FIFOMODE_FIFO;
      fifo_cfg.FIFOSize = FIFOSIZE_4KB;                       /* 4kB for FIFO, The reset 2kB for sequencer */
      fifo_cfg.FIFOSrc = FIFOSRC_DFT;
      fifo_cfg.FIFOThresh = AppIMPCfg.FifoThresh;              /* DFT result. One pair for RCAL, another for Rz. One DFT result have real part and imaginary part */
      AD5940_FIFOCfg(&fifo_cfg);
      AD5940_INTCClrFlag(AFEINTSRC_ALLINT);
    
      /* Start sequence generator */
      /* Initialize sequencer generator */
      if((AppIMPCfg.IMPInited == bFALSE)||\
           (AppIMPCfg.bParaChanged == bTRUE))
      {
        if(pBuffer == 0)  return AD5940ERR_PARA;
        if(BufferSize == 0) return AD5940ERR_PARA;   
        AD5940_SEQGenInit(pBuffer, BufferSize);
    
        /* Generate initialize sequence */
        error = AppIMPSeqCfgGen(); /* Application initialization sequence using either MCU or sequencer */
        if(error != AD5940ERR_OK) return error;
    
        /* Generate measurement sequence */
        error = AppIMPSeqMeasureGen();
        if(error != AD5940ERR_OK) return error;
    
        AppIMPCfg.bParaChanged = bFALSE; /* Clear this flag as we already implemented the new configuration */
      }
    
      /* Initialization sequencer  */
      AppIMPCfg.InitSeqInfo.WriteSRAM = bFALSE;
      AD5940_SEQInfoCfg(&AppIMPCfg.InitSeqInfo);
      seq_cfg.SeqEnable = bTRUE;
      AD5940_SEQCfg(&seq_cfg);  /* Enable sequencer */
      AD5940_SEQMmrTrig(AppIMPCfg.InitSeqInfo.SeqId);
      while(AD5940_INTCTestFlag(AFEINTC_1, AFEINTSRC_ENDSEQ) == bFALSE);
      
      /* Measurement sequence  */
      AppIMPCfg.MeasureSeqInfo.WriteSRAM = bFALSE;
      AD5940_SEQInfoCfg(&AppIMPCfg.MeasureSeqInfo);
      
      AppIMPCheckFreq(AppIMPCfg.FreqofData);
    
      seq_cfg.SeqEnable = bTRUE;
      AD5940_SEQCfg(&seq_cfg);  /* Enable sequencer, and wait for trigger */
      AD5940_ClrMCUIntFlag();   /* Clear interrupt flag generated before */
    
      AD5940_AFEPwrBW(AppIMPCfg.PwrMod, AFEBW_250KHZ);
    
    	AD5940_WriteReg(REG_AFE_LPTIASW0, 0x3180);
      AppIMPCfg.IMPInited = bTRUE;  /* IMP application has been initialized. */
      return AD5940ERR_OK;
    }
    
    /* Modify registers when AFE wakeup */
    int32_t AppIMPRegModify(int32_t * const pData, uint32_t *pDataCount)
    {
      if(AppIMPCfg.NumOfData > 0)
      {
        AppIMPCfg.FifoDataCount += *pDataCount/4;
        if(AppIMPCfg.FifoDataCount >= AppIMPCfg.NumOfData)
        {
          AD5940_WUPTCtrl(bFALSE);
          return AD5940ERR_OK;
        }
      }
      if(AppIMPCfg.StopRequired == bTRUE)
      {
        AD5940_WUPTCtrl(bFALSE);
        return AD5940ERR_OK;
      }
      if(AppIMPCfg.SweepCfg.SweepEn) /* Need to set new frequency and set power mode */
      {
    		/* Check frequency and update FIlter settings */
        AD5940_WGFreqCtrlS(AppIMPCfg.SweepNextFreq, AppIMPCfg.SysClkFreq);
    	AppIMPCheckFreq(AppIMPCfg.SweepNextFreq);
      }
      return AD5940ERR_OK;
    }
    
    /* Depending on the data type, do appropriate data pre-process before return back to controller */
    int32_t AppIMPDataProcess(int32_t * const pData, uint32_t *pDataCount)
    {
      uint32_t DataCount = *pDataCount;
      uint32_t ImpResCount = DataCount/6;
      
      fImpPol_Type * const pOut = (fImpPol_Type*)pData;
      iImpCar_Type * pSrcData = (iImpCar_Type*)pData;
      
      *pDataCount = 0;
      
      DataCount = (DataCount/6)*6;/* We expect Rz+Rload, Rload and RCAL data, . One DFT result has two data in FIFO, real part and imaginary part.  */
      
      /* Convert DFT result to int32_t type */
      for(uint32_t i=0; i<DataCount; i++)
      {
        pData[i] &= 0x3ffff;
        if(pData[i]&(1L<<17)) /* Bit17 is sign bit */
        {
          pData[i] |= 0xfffc0000; /* Data is 18bit in two's complement, bit17 is the sign bit */
        }
      }
      for(uint32_t i=0; i<ImpResCount; i++)
      {
        if(1)
        {
          fImpCar_Type DftRcal, DftRzRload, DftRload, temp1, temp2, res;
          fImpCar_Type DftConst1 = {1.0f, 0};
          /*
            The sign of DFT Image result is added '-1' by hardware. Fix it below.
          */
          DftRzRload.Real = pSrcData->Real;
          DftRzRload.Image = -pSrcData->Image;
          pSrcData++;
          DftRload.Real = pSrcData->Real;
          DftRload.Image = -pSrcData->Image;
          pSrcData++;
          DftRcal.Real = pSrcData->Real;
          DftRcal.Image = -pSrcData->Image;
          pSrcData++;
          /**
            Rz = RloadRz - Rload
            RloadRz = DftRcal/DftRzRload*RCAL;
            Rload = DftRcal/DftRload*RCAL;
            Rz = RloadRz - Rload = 
                 (1/DftRzRload - 1/DftRload)*DftRcal*RCAL;
            where RCAL is the RCAL resistor value in Ohm.
          */
          //temp1 = 1/DftRzRload;
          //temp2 = 1/DftRload;
          temp1 = AD5940_ComplexDivFloat(&DftConst1, &DftRzRload); 
          temp2 = AD5940_ComplexDivFloat(&DftConst1, &DftRload); 
          res = AD5940_ComplexSubFloat(&temp1, &temp2);
          res = AD5940_ComplexMulFloat(&res, &DftRcal);
          pOut[i].Magnitude = AD5940_ComplexMag(&res)*AppIMPCfg.RcalVal;
          pOut[i].Phase = AD5940_ComplexPhase(&res);
        }
        else
        {
          iImpCar_Type *pDftRcal, *pDftRzRload, *pDftRload;
          
          pDftRzRload = pSrcData++;
          pDftRload = pSrcData++;
          pDftRcal = pSrcData++;
          
          float RzRloadMag, RzRloadPhase;
          float RloadMag, RloadPhase;
          float RzMag,RzPhase;
          float RcalMag, RcalPhase;
          float RzReal, RzImage;
          
          RzReal = pDftRload->Real - pDftRzRload->Real;
          RzImage = pDftRload->Image - pDftRzRload->Image;
          
          RzRloadMag = sqrt((float)pDftRzRload->Real*pDftRzRload->Real+(float)pDftRzRload->Image*pDftRzRload->Image);
          RzRloadPhase = atan2(-pDftRzRload->Image,pDftRzRload->Real);
          RcalMag = sqrt((float)pDftRcal->Real*pDftRcal->Real+(float)pDftRcal->Image*pDftRcal->Image);
          RcalPhase = atan2(-pDftRcal->Image,pDftRcal->Real);
          RzMag = sqrt((float)RzReal*RzReal+(float)RzImage*RzImage);
          RzPhase = atan2(-RzImage,RzReal);
          RloadMag = sqrt((float)pDftRload->Real*pDftRload->Real+(float)pDftRload->Image*pDftRload->Image);
          RloadPhase = atan2(-pDftRload->Image,pDftRload->Real);
          
          RzMag = (AppIMPCfg.RcalVal*RcalMag*RzMag)/(RzRloadMag*RloadMag);
          RzPhase = -(RcalPhase + RzPhase - RloadPhase - RzRloadPhase);
         // RzPhase = (RcalPhase + RzPhase - RloadPhase - RzRloadPhase);
    
          
          pOut[i].Magnitude = RzMag;
          pOut[i].Phase = RzPhase;
        }
      }
      *pDataCount = ImpResCount; 
      AppIMPCfg.FreqofData = AppIMPCfg.SweepCurrFreq;
      /* Calculate next frequency point */
      if(AppIMPCfg.SweepCfg.SweepEn == bTRUE)
      {
        AppIMPCfg.FreqofData = AppIMPCfg.SweepCurrFreq;
        AppIMPCfg.SweepCurrFreq = AppIMPCfg.SweepNextFreq;
        AD5940_SweepNext(&AppIMPCfg.SweepCfg, &AppIMPCfg.SweepNextFreq);
      }
    
      return 0;
    }
    
    /**
    
    */
    int32_t AppIMPISR(void *pBuff, uint32_t *pCount)
    {
      uint32_t BuffCount;
      uint32_t FifoCnt;
      BuffCount = *pCount;
      
      *pCount = 0;
      
      if(AD5940_WakeUp(10) > 10)  /* Wakeup AFE by read register, read 10 times at most */
        return AD5940ERR_WAKEUP;  /* Wakeup Failed */
      AD5940_SleepKeyCtrlS(SLPKEY_LOCK);  /* Prohibit AFE to enter sleep mode. */
    
      if(AD5940_INTCTestFlag(AFEINTC_0, AFEINTSRC_DATAFIFOTHRESH) == bTRUE)
      {
        /* Now there should be 4 data in FIFO */
        FifoCnt = (AD5940_FIFOGetCnt()/6)*6;
        
        if(FifoCnt > BuffCount)
        {
          ///@todo buffer is limited.
        }
        AD5940_FIFORd((uint32_t *)pBuff, FifoCnt);
        AD5940_INTCClrFlag(AFEINTSRC_DATAFIFOTHRESH);
        AppIMPRegModify(pBuff, &FifoCnt);   /* If there is need to do AFE re-configure, do it here when AFE is in active state */
        //AD5940_EnterSleepS(); /* Manually put AFE back to hibernate mode. This operation only takes effect when register value is ACTIVE previously */
        AD5940_SleepKeyCtrlS(SLPKEY_UNLOCK);  /* Allow AFE to enter sleep mode. */
        /* Process data */ 
        AppIMPDataProcess((int32_t*)pBuff,&FifoCnt); 
        *pCount = FifoCnt;
        return 0;
      }
      
      return 0;
    } 

    Impedance.h :-

    /*!
     *****************************************************************************
     @file:    Impedance.h
     @author:  Neo Xu
     @brief:   Electrochemical impedance spectroscopy based on example AD5940_Impedance
     -----------------------------------------------------------------------------
    
    Copyright (c) 2017-2019 Analog Devices, Inc. All Rights Reserved.
    
    This software is proprietary to Analog Devices, Inc. and its licensors.
    By using this software you agree to the terms of the associated
    Analog Devices Software License Agreement.
     
    *****************************************************************************/
    #ifndef _IMPEDANCESEQUENCES_H_
    #define _IMPEDANCESEQUENCES_H_
    #include "AD5940.H"
    #include <stdio.h>
    #include "string.h"
    #include "math.h"
    
    typedef struct
    {
    /* Common configurations for all kinds of Application. */
      BoolFlag bParaChanged;        /* Indicate to generate sequence again. It's auto cleared by AppBIAInit */
      uint32_t SeqStartAddr;        /* Initialaztion sequence start address in SRAM of AD5940  */
      uint32_t MaxSeqLen;           /* Limit the maximum sequence.   */
      uint32_t SeqStartAddrCal;     /* Measurement sequence start address in SRAM of AD5940 */
      uint32_t SeqWaitAddr[3];        
      uint32_t MaxSeqLenCal;
    /* Application related parameters */ 
      float ImpODR;                 /*  */
      int32_t NumOfData;            /* By default it's '-1'. If you want the engine stops after get NumofData, then set the value here. Otherwise, set it to '-1' which means never stop. */
      float WuptClkFreq;            /* The clock frequency of Wakeup Timer in Hz. Typically it's 32kHz. Leave it here in case we calibrate clock in software method */
      float SysClkFreq;             /* The real frequency of system clock */
      float AdcClkFreq;             /* The real frequency of ADC clock */
      float RcalVal;                /* Rcal value in Ohm */
      /* Switch Configuration */
      uint32_t DswitchSel;
      uint32_t PswitchSel;
      uint32_t NswitchSel;
      uint32_t TswitchSel;
      uint32_t PwrMod;              /* Control Chip power mode(LP/HP) */
      uint32_t HstiaRtiaSel;        /* Use internal RTIA, select from RTIA_INT_200, RTIA_INT_1K, RTIA_INT_5K, RTIA_INT_10K, RTIA_INT_20K, RTIA_INT_40K, RTIA_INT_80K, RTIA_INT_160K */
      uint32_t ExcitBufGain;        /* Select from  EXCTBUFGAIN_2, EXCTBUFGAIN_0P25 */     
      uint32_t HsDacGain;           /* Select from  HSDACGAIN_1, HSDACGAIN_0P2 */
      uint32_t HsDacUpdateRate;
      float DacVoltPP;              /* DAC output voltage in mV peak to peak. Maximum value is 600mVpp. Peak to peak voltage  */
      float BiasVolt;               /* The excitation signal is DC+AC. This parameter decides the DC value in mV unit. 0.0mV means no DC bias.*/
      float SinFreq;                /* Frequency of excitation signal */
      uint32_t DftNum;              /* DFT number */
      uint32_t DftSrc;              /* DFT Source */
      BoolFlag HanWinEn;            /* Enable Hanning window */
      uint32_t AdcPgaGain;          /* PGA Gain select from GNPGA_1, GNPGA_1_5, GNPGA_2, GNPGA_4, GNPGA_9 !!! We must ensure signal is in range of +-1.5V which is limited by ADC input stage */   
      uint8_t ADCSinc3Osr;
      uint8_t ADCSinc2Osr;  
      uint8_t ADCAvgNum;
    	uint8_t ADC_Rate;
    	
    	uint32_t LptiaRtiaSel;        /* Use internal RTIA, select from RTIA_INT_200, RTIA_INT_1K, RTIA_INT_5K, RTIA_INT_10K, RTIA_INT_20K, RTIA_INT_40K, RTIA_INT_80K, RTIA_INT_160K */
      uint32_t LpTiaRf;             /* Rfilter select */
      uint32_t LpTiaRl;             /* SE0 Rload select */
    	float Vzero;                  /* Voltage on SE0 pin and Vzero, optimumly 1100mV*/
      float Vbias;                  /* Voltage on CE0 and PA */
      /* Sweep Function Control */
      SoftSweepCfg_Type SweepCfg;
      uint32_t FifoThresh;           /* FIFO threshold. Should be N*4 */
    /* Private variables for internal usage */
    /* Private variables for internal usage */
      float SweepCurrFreq;
      float SweepNextFreq;
      float FreqofData;                         /* The frequency of latest data sampled */
      BoolFlag IMPInited;                       /* If the program run firstly, generated sequence commands */
      SEQInfo_Type InitSeqInfo;
      SEQInfo_Type MeasureSeqInfo;
      BoolFlag StopRequired;          /* After FIFO is ready, stop the measurement sequence */
      uint32_t FifoDataCount;         /* Count how many times impedance have been measured */
    }AppIMPCfg_Type;
    
    #define IMPCTRL_START          0
    #define IMPCTRL_STOPNOW        1
    #define IMPCTRL_STOPSYNC       2
    #define IMPCTRL_GETFREQ        3   /* Get Current frequency of returned data from ISR */
    #define IMPCTRL_SHUTDOWN       4   /* Note: shutdown here means turn off everything and put AFE to hibernate mode. The word 'SHUT DOWN' is only used here. */
    
    
    int32_t AppIMPInit(uint32_t *pBuffer, uint32_t BufferSize);
    int32_t AppIMPGetCfg(void *pCfg);
    int32_t AppIMPISR(void *pBuff, uint32_t *pCount);
    int32_t AppIMPCtrl(uint32_t Command, void *pPara);
    
    #endif
    

  • Hello  ,

    Thank you for providing the above code. I would like to clarify a couple of things.

    1. The filter settings are adjusted in the AppIMPCheckFreq() function.

    2. The AppIMPCheckFreq() function is called in the AppIMPRegModify() function when the sweep frequency is updated.

    3. An additional element is added to the AppIMPcfg_Type structure, SeqWaitAddr[], which is updated in the AppIMPCheckFreq() function.

    From what I can see, these are the major differences between the code provided in the above post and the code provided on  's GitHub repository (https://github.com/analogdevicesinc/ad5940-examples/tree/master/examples/AD5940_Impedance). Are the listed steps correct? Are there any additional steps, aside from those listed above?

    In addition, when I go to take a measurement with the above code, how long should I expect the measurement of the lower frequencies to be? How long should I expect the total measurement to be?

    Thank you for your assistance.

  • Hi,

    Yes. The listed points are correct. No additional steps required (You may keep ODR value very small and run)

    For small frequencies (<5Hz), it may take as long as 3 minutes for one measurement.

  • Hello  ,

    Thank you for the clarification.