outputting the voltage in the Ramp code for Cyclic Voltammetry

Hi,

You may add a line in AppRAMPDataProcess() as below:

static int32_t AppRAMPDataProcess(int32_t *const pData, uint32_t *pDataCount)
{
uint32_t i, datacount;
datacount = *pDataCount;
float *pOut = (float *)pData;
float temp;
for(i = 0; i < datacount; i++)
{
pData[i] &= 0xffff;
temp = -AD5940_ADCCode2Volt(pData[i], AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);

printf(printf("Ramp voltage: %f \n", temp);

pOut[i] = temp / AppRAMPCfg.RtiaValue.Magnitude * 1e3f; /* Result unit is uA. */
}
return 0;
}

Hi Akila,

Thanks for the reply -- but this isn't quite what I'm looking for. I'm trying to get the ramp voltage -- i.e. the voltage that's being applied (the one that's shaped like two sides of a triangle), not the output current transformed into a voltage. I realize it's possible to calculate it based on the input parameters, but I'd like to also output it as a sanity check.

Hi,

You may modify AppRAMPSeqADCCtrlGen() as below:

static AD5940Err AppRAMPSeqADCCtrlGen(void)
{
AD5940Err error = AD5940ERR_OK;
const uint32_t *pSeqCmd;
uint32_t SeqLen;
DSPCfg_Type dsp_cfg;

uint32_t WaitClks;
ClksCalInfo_Type clks_cal;

clks_cal.DataCount = 1; /* Sample one point everytime */
clks_cal.DataType = DATATYPE_SINC3;
clks_cal.ADCSinc3Osr = AppRAMPCfg.ADCSinc3Osr;
clks_cal.ADCSinc2Osr = ADCSINC2OSR_1067; /* Don't care */
clks_cal.ADCAvgNum = ADCAVGNUM_2; /* Don't care */
clks_cal.RatioSys2AdcClk = AppRAMPCfg.SysClkFreq / AppRAMPCfg.AdcClkFreq;
AD5940_ClksCalculate(&clks_cal, &WaitClks);

AD5940_StructInit(&dsp_cfg, sizeof(dsp_cfg));
dsp_cfg.ADCBaseCfg.ADCPga = AppRAMPCfg.AdcPgaGain;
dsp_cfg.ADCFilterCfg.ADCSinc3Osr = AppRAMPCfg.ADCSinc3Osr;
dsp_cfg.ADCFilterCfg.ADCRate = ADCRATE_800KHZ; /* ADC runs at 16MHz clock in this example, sample rate is 800kHz */
dsp_cfg.ADCFilterCfg.BpSinc3 = bFALSE; /* We use data from SINC3 filter */
dsp_cfg.ADCFilterCfg.Sinc2NotchEnable = bTRUE;
dsp_cfg.ADCFilterCfg.BpNotch = bTRUE;
dsp_cfg.ADCFilterCfg.ADCSinc2Osr = ADCSINC2OSR_1067; /* Don't care */
dsp_cfg.ADCFilterCfg.ADCAvgNum = ADCAVGNUM_2; /* Don't care because it's disabled */

AD5940_SEQGenCtrl(bTRUE);
/*Measure ramp voltage*/
dsp_cfg.ADCBaseCfg.ADCMuxN = ADCMUXN_VZERO0
dsp_cfg.ADCBaseCfg.ADCMuxP = ADCMUXP_VBIAS0
AD5940_DSPCfgS(&dsp_cfg);

AD5940_SEQGpioCtrlS(AGPIO_Pin2);
AD5940_AFECtrlS(AFECTRL_ADCPWR, bTRUE);
AD5940_SEQGenInsert(SEQ_WAIT(16 * 250)); /* wait 250us for reference power up */
AD5940_AFECtrlS(AFECTRL_ADCCNV, bTRUE); /* Start ADC convert */
AD5940_SEQGenInsert(SEQ_WAIT(WaitClks)); /* wait for first data ready */
AD5940_AFECtrlS(AFECTRL_ADCPWR | AFECTRL_ADCCNV, bFALSE); /* Stop ADC */
AD5940_SEQGpioCtrlS(0);

/*Measure CV response*/
dsp_cfg.ADCBaseCfg.ADCMuxN = ADCMUXN_LPTIA0_N;//ADCMUXN_VZERO0
dsp_cfg.ADCBaseCfg.ADCMuxP = ADCMUXP_LPTIA0_P;//ADCMUXP_VBIAS0
AD5940_DSPCfgS(&dsp_cfg);

AD5940_SEQGpioCtrlS(AGPIO_Pin2);
AD5940_AFECtrlS(AFECTRL_ADCPWR, bTRUE);
AD5940_SEQGenInsert(SEQ_WAIT(16 * 250)); /* wait 250us for reference power up */
AD5940_AFECtrlS(AFECTRL_ADCCNV, bTRUE); /* Start ADC convert*/
AD5940_SEQGenInsert(SEQ_WAIT(WaitClks)); /* wait for first data ready */
AD5940_AFECtrlS(AFECTRL_ADCPWR | AFECTRL_ADCCNV, bFALSE); /* Stop ADC */
AD5940_SEQGpioCtrlS(0);
AD5940_EnterSleepS();/* Goto hibernate */
/* Sequence end. */
error = AD5940_SEQGenFetchSeq(&pSeqCmd, &SeqLen);
AD5940_SEQGenCtrl(bFALSE); /* Stop sequencer generator */

if(error == AD5940ERR_OK)
{
AD5940_StructInit(&AppRAMPCfg.ADCSeqInfo, sizeof(AppRAMPCfg.ADCSeqInfo));
if((SeqLen + AppRAMPCfg.InitSeqInfo.SeqLen) >= AppRAMPCfg.MaxSeqLen)
return AD5940ERR_SEQLEN;
AppRAMPCfg.ADCSeqInfo.SeqId = SEQID_2;
AppRAMPCfg.ADCSeqInfo.SeqRamAddr = AppRAMPCfg.InitSeqInfo.SeqRamAddr + AppRAMPCfg.InitSeqInfo.SeqLen ;
AppRAMPCfg.ADCSeqInfo.pSeqCmd = pSeqCmd;
AppRAMPCfg.ADCSeqInfo.SeqLen = SeqLen;
AppRAMPCfg.ADCSeqInfo.WriteSRAM = bTRUE;
AD5940_SEQInfoCfg(&AppRAMPCfg.ADCSeqInfo);
}
else
return error; /* Error */
return AD5940ERR_OK;
}

and you may modify AppRAMPDataProcess() as below:

static int32_t AppRAMPDataProcess(int32_t *const pData, uint32_t *pDataCount)
{
uint32_t i, datacount;
datacount = *pDataCount;
float *pVolt, *pCurrent;
float *pOut = (float *)pData;
float temp;
for(i = 0; i < datacount; i++)
{
pVolt = pData++;
pCurrent = pData;
pVolt &= 0xffff;
temp = -AD5940_ADCCode2Volt(pVolt, AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);
Printf("Vbias - Vzero = %f/n",temp);

pCurrent &= 0xffff;
temp = -AD5940_ADCCode2Volt(pCurrent, AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);
pOut[i] = temp / AppRAMPCfg.RtiaValue.Magnitude * 1e3f; /* Result unit is uA. */
}
return 0;
}

Via code, any measurement alteast goes through ADC. Can't measure it directly before ADC.

Hi Akila,

Thanks for this! This is super helpful. A few follow-up questions.

1. In the original AppRAMPSeqADCCtrlGen code, AD5940_SEQGenCtrl(bTRUE); gets called once right before  AD5940_SEQGpioCtrlS(AGPIO_Pin2); -- in this revised code it still only get called once right before "Measure Ramp Voltage" - can you confirm that it only needs to get called a single time?
   
   
2. I'm aconfused about the revised code in AppRAMPDataProcess  - specifically:
   1. pVolt = pData++;  this throws an error: cannot assign to variable 'pData' with const qualified type. Given that pData is a const, I don't see how you can increment it. Also, how can you assign pData to pVolt when the latter is a float and the former is an int? Should I be trying to increment i instead of pData? is the pData array now alternating voltage / current values?
      
   2. Indeed, on the line pCurrent = pData; I get an incompatible pointer types warning because it assigns a const int pointer to a float pointer. 
   3. on the line  pVolt &= 0xffff; I get an error "invalid operands to binary expression ('float *' and 'int') - I get the idea that I'm doing this AND in order only look at the last 16 bits of pVolt, but this doesn't seem to work.
      
      
   4. on the line  temp = -AD5940_ADCCode2Volt(pVolt, AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt); - i also get a warning because AD5940_ADCCode2Volt expects an unsigned int to be the first argument but I'm passing a float *. 
      

thanks again!

hi,

1) Yes, it needs to be called only once.

2) Yes.You may modify as below:

static int32_t AppRAMPDataProcess(int32_t *const pData, uint32_t *pDataCount)
{
uint32_t i, datacount;
datacount = *pDataCount;
int32_t pVolt, pCurrent;
float *pOut = (float *)pData;
float temp;
for(i = 0; i < datacount; i++)
{
pVolt = pData[i++];
pCurrent = pData[i];
pVolt &= 0xffff;
temp = -AD5940_ADCCode2Volt(pVolt, AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);
printf("Vbias - Vzero = %f/n",temp);

pCurrent &= 0xffff;
temp = -AD5940_ADCCode2Volt(pCurrent, AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);
pOut[i] = temp / AppRAMPCfg.RtiaValue.Magnitude * 1e3f; /* Result unit is uA. */
}
return 0;
}

Thanks! Ok, this runs now - however, the voltages I get out don't make sense. 

For example, setting vstart to -0.6V and vpeak to 1V, and vzero_start and vzero_peak to -0.6V I get the following when I plot the voltage:

The corresponding current plot does make sense (I get the expected peaks), so it seems clear that the applied voltage isn't right:

Any advice on how to proceed?

thanks again!

Thanks! Ok, this runs now - however, the voltages I get out don't make sense. 

For example, setting vstart to -0.6V and vpeak to 1V, and vzero_start and vzero_peak to -0.6V I get the following when I plot the voltage:

The corresponding current plot does make sense (I get the expected peaks), so it seems clear that the applied voltage isn't right:

Any advice on how to proceed?

thanks again!

Hi Akila - Circling back to this - do you have any advice on how to proceed? Thank you!

Hi Akila - me again - have you verified that this code works on your side? I went through line by line and I don't see any differences between our code and yours. 

Hi,

With the modifications below, I am getting the plot below:

Series1 = (Vbias - Vzero)

Series2 = Current output in uA

Code:-

static int32_t RampShowResult(float *pData, uint32_t DataCount)
{
static uint32_t index;
/* Print data*/
for(int i=0;i<DataCount;i++)
{
printf("index:%d,Vbias-Vzero0 = %.3f, Current =%.3f\n", index++, pData[i++], pData[i]);
//i += 10; /* Print though UART consumes too much time. */
}
return 0;
}

static int32_t AppRAMPDataProcess(int32_t *const pData, uint32_t *pDataCount)
{
uint32_t i, datacount;
datacount = *pDataCount;
float *pOut = (float *)pData;
float temp1, temp;
for(i = 0; i < datacount; i++)
{
pData[i] &= 0xffff;
temp1 = AD5940_ADCCode2Volt(pData[i], AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);
pOut[i++] = temp1;

pData[i] &= 0xffff;
temp = -AD5940_ADCCode2Volt(pData[i], AppRAMPCfg.AdcPgaGain, AppRAMPCfg.ADCRefVolt);
pOut[i] = temp / AppRAMPCfg.RtiaValue.Magnitude * 1e3f; /* Result unit is uA. */

}
return 0;
}

static AD5940Err AppRAMPSeqInitGen(void)
{
AD5940Err error = AD5940ERR_OK;
const uint32_t *pSeqCmd;
uint32_t SeqLen;
AFERefCfg_Type aferef_cfg;
LPLoopCfg_Type lploop_cfg;
DSPCfg_Type dsp_cfg;
/* 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;
/* LP reference control - turn off them to save power*/
aferef_cfg.LpBandgapEn = bTRUE;
aferef_cfg.LpRefBufEn = bTRUE;
aferef_cfg.LpRefBoostEn = bFALSE;
AD5940_REFCfgS(&aferef_cfg);

lploop_cfg.LpAmpCfg.LpAmpSel = LPAMP0;
lploop_cfg.LpAmpCfg.LpAmpPwrMod = LPAMPPWR_BOOST3;
lploop_cfg.LpAmpCfg.LpPaPwrEn = bTRUE;
lploop_cfg.LpAmpCfg.LpTiaPwrEn = bTRUE;
lploop_cfg.LpAmpCfg.LpTiaRf = LPTIARF_20K;
lploop_cfg.LpAmpCfg.LpTiaRload = AppRAMPCfg.LPTIARloadSel;
lploop_cfg.LpAmpCfg.LpTiaRtia = AppRAMPCfg.LPTIARtiaSel;
if(AppRAMPCfg.LPTIARtiaSel == LPTIARTIA_OPEN) /* User want to use external RTIA */
lploop_cfg.LpAmpCfg.LpTiaSW = LPTIASW(2) | LPTIASW(4) | LPTIASW(5) | LPTIASW(9)/*|LPTIASW(10)*/; /* SW5/9 is closed to support external RTIA resistor */
else
lploop_cfg.LpAmpCfg.LpTiaSW = LPTIASW(2)|LPTIASW(4)|LPTIASW(5);

lploop_cfg.LpDacCfg.LpdacSel = LPDAC0;
lploop_cfg.LpDacCfg.DacData12Bit = 0x800;
lploop_cfg.LpDacCfg.DacData6Bit = 0;
lploop_cfg.LpDacCfg.DataRst = bFALSE;
lploop_cfg.LpDacCfg.LpDacSW = LPDACSW_VBIAS2LPPA|LPDACSW_VBIAS2PIN | LPDACSW_VZERO2LPTIA|LPDACSW_VZERO2PIN;
lploop_cfg.LpDacCfg.LpDacRef = LPDACREF_2P5;
lploop_cfg.LpDacCfg.LpDacSrc = LPDACSRC_MMR;
lploop_cfg.LpDacCfg.LpDacVbiasMux = LPDACVBIAS_12BIT; /* Step Vbias. Use 12bit DAC ouput */
lploop_cfg.LpDacCfg.LpDacVzeroMux = LPDACVZERO_6BIT; /* Base is Vzero. Use 6 bit DAC ouput */
lploop_cfg.LpDacCfg.PowerEn = bTRUE;
AD5940_LPLoopCfgS(&lploop_cfg);

AD5940_StructInit(&dsp_cfg, sizeof(dsp_cfg));
dsp_cfg.ADCBaseCfg.ADCMuxN = ADCMUXN_VZERO0;//ADCMUXN_LPTIA0_N;
dsp_cfg.ADCBaseCfg.ADCMuxP = ADCMUXP_VBIAS0;//ADCMUXP_LPTIA0_P;
dsp_cfg.ADCBaseCfg.ADCPga = AppRAMPCfg.AdcPgaGain;

dsp_cfg.ADCFilterCfg.ADCSinc3Osr = AppRAMPCfg.ADCSinc3Osr;
dsp_cfg.ADCFilterCfg.ADCRate = ADCRATE_800KHZ; /* ADC runs at 16MHz clock in this example, sample rate is 800kHz */
dsp_cfg.ADCFilterCfg.BpSinc3 = bFALSE; /* We use data from SINC3 filter */
dsp_cfg.ADCFilterCfg.Sinc2NotchEnable = bTRUE;
dsp_cfg.ADCFilterCfg.BpNotch = bTRUE;
dsp_cfg.ADCFilterCfg.ADCSinc2Osr = ADCSINC2OSR_1067; /* Don't care */
dsp_cfg.ADCFilterCfg.ADCAvgNum = ADCAVGNUM_2; /* Don't care because it's disabled */
AD5940_DSPCfgS(&dsp_cfg);

/* 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 sequence generator here */
AD5940_SEQGenCtrl(bFALSE); /* Stop sequencer generator */
error = AD5940_SEQGenFetchSeq(&pSeqCmd, &SeqLen);
if(error == AD5940ERR_OK)
{
AD5940_StructInit(&AppRAMPCfg.InitSeqInfo, sizeof(AppRAMPCfg.InitSeqInfo));
if(SeqLen >= AppRAMPCfg.MaxSeqLen)
return AD5940ERR_SEQLEN;

AppRAMPCfg.InitSeqInfo.SeqId = SEQID_3;
AppRAMPCfg.InitSeqInfo.SeqRamAddr = AppRAMPCfg.SeqStartAddr;
AppRAMPCfg.InitSeqInfo.pSeqCmd = pSeqCmd;
AppRAMPCfg.InitSeqInfo.SeqLen = SeqLen;
AppRAMPCfg.InitSeqInfo.WriteSRAM = bTRUE;
AD5940_SEQInfoCfg(&AppRAMPCfg.InitSeqInfo);
}
else
return error; /* Error */
return AD5940ERR_OK;
}

static AD5940Err AppRAMPSeqADCCtrlGen(void)
{
AD5940Err error = AD5940ERR_OK;
const uint32_t *pSeqCmd;
uint32_t SeqLen;

uint32_t WaitClks;
ClksCalInfo_Type clks_cal;
DSPCfg_Type dsp_cfg;

clks_cal.DataCount = 1; /* Sample one point everytime */
clks_cal.DataType = DATATYPE_SINC3;
clks_cal.ADCSinc3Osr = AppRAMPCfg.ADCSinc3Osr;
clks_cal.ADCSinc2Osr = ADCSINC2OSR_1067; /* Don't care */
clks_cal.ADCAvgNum = ADCAVGNUM_2; /* Don't care */
clks_cal.RatioSys2AdcClk = AppRAMPCfg.SysClkFreq / AppRAMPCfg.AdcClkFreq;
AD5940_ClksCalculate(&clks_cal, &WaitClks);

AD5940_SEQGenCtrl(bTRUE);
AD5940_SEQGpioCtrlS(AGPIO_Pin2);
AD5940_AFECtrlS(AFECTRL_ADCPWR, bTRUE);
AD5940_SEQGenInsert(SEQ_WAIT(16 * 250)); /* wait 250us for reference power up */
AD5940_AFECtrlS(AFECTRL_ADCCNV, bTRUE); /* Start ADC convert and DFT */
AD5940_SEQGenInsert(SEQ_WAIT(WaitClks)); /* wait for first data ready */
AD5940_AFECtrlS(AFECTRL_ADCPWR | AFECTRL_ADCCNV, bFALSE); /* Stop ADC */

AD5940_StructInit(&dsp_cfg, sizeof(dsp_cfg));

dsp_cfg.ADCBaseCfg.ADCMuxN = ADCMUXN_LPTIA0_N;
dsp_cfg.ADCBaseCfg.ADCMuxP = ADCMUXP_LPTIA0_P;
dsp_cfg.ADCBaseCfg.ADCPga = AppRAMPCfg.AdcPgaGain;

dsp_cfg.ADCFilterCfg.ADCSinc3Osr = AppRAMPCfg.ADCSinc3Osr;
dsp_cfg.ADCFilterCfg.ADCRate = ADCRATE_800KHZ; /* ADC runs at 16MHz clock in this example, sample rate is 800kHz */
dsp_cfg.ADCFilterCfg.BpSinc3 = bFALSE; /* We use data from SINC3 filter */
dsp_cfg.ADCFilterCfg.Sinc2NotchEnable = bTRUE;
dsp_cfg.ADCFilterCfg.BpNotch = bTRUE;
dsp_cfg.ADCFilterCfg.ADCSinc2Osr = ADCSINC2OSR_1067; /* Don't care */
dsp_cfg.ADCFilterCfg.ADCAvgNum = ADCAVGNUM_2; /* Don't care because it's disabled */
AD5940_DSPCfgS(&dsp_cfg);

AD5940_AFECtrlS(AFECTRL_ADCPWR, bTRUE);
AD5940_SEQGenInsert(SEQ_WAIT(16 * 250)); /* wait 250us for reference power up */
AD5940_AFECtrlS(AFECTRL_ADCCNV, bTRUE); /* Start ADC convert and DFT */
AD5940_SEQGenInsert(SEQ_WAIT(WaitClks)); /* wait for first data ready */
AD5940_AFECtrlS(AFECTRL_ADCPWR | AFECTRL_ADCCNV, bFALSE); /* Stop ADC */

AD5940_SEQGpioCtrlS(0);
AD5940_EnterSleepS();/* Goto hibernate */
/* Sequence end. */
error = AD5940_SEQGenFetchSeq(&pSeqCmd, &SeqLen);
AD5940_SEQGenCtrl(bFALSE); /* Stop sequencer generator */

if(error == AD5940ERR_OK)
{
AD5940_StructInit(&AppRAMPCfg.ADCSeqInfo, sizeof(AppRAMPCfg.ADCSeqInfo));
if((SeqLen + AppRAMPCfg.InitSeqInfo.SeqLen) >= AppRAMPCfg.MaxSeqLen)
return AD5940ERR_SEQLEN;
AppRAMPCfg.ADCSeqInfo.SeqId = SEQID_2;
AppRAMPCfg.ADCSeqInfo.SeqRamAddr = AppRAMPCfg.InitSeqInfo.SeqRamAddr + AppRAMPCfg.InitSeqInfo.SeqLen ;
AppRAMPCfg.ADCSeqInfo.pSeqCmd = pSeqCmd;
AppRAMPCfg.ADCSeqInfo.SeqLen = SeqLen;
AppRAMPCfg.ADCSeqInfo.WriteSRAM = bTRUE;
AD5940_SEQInfoCfg(&AppRAMPCfg.ADCSeqInfo);
}
else
return error; /* Error */
return AD5940ERR_OK;
}

Hi Akila, 

I think I'm confused because my expectation is that the voltage would ramp upward and then downward, not simply decreasing monotonically. For example, when I run CV using sensorpal I see that the voltage increases and then decreases. Am I missing something? 

thanks again!

Hi,

If you capture for a long duration, you will get both the upward and downward phases:

Also, you may modify the lines as below:

wupt_cfg.SeqxWakeupTime[SEQID_2] = (uint32_t)(2*(AppRAMPCfg.LFOSCClkFreq * AppRAMPCfg.SampleDelay / 1000.0f)) - 4 - 2;
wupt_cfg.SeqxSleepTime[SEQID_0] = 4;
wupt_cfg.SeqxWakeupTime[SEQID_0] = (uint32_t)(2*(AppRAMPCfg.LFOSCClkFreq * (AppRAMPCfg.RampDuration / AppRAMPCfg.StepNumber - AppRAMPCfg.SampleDelay) / 1000.0f)) - 4 - 2;

Hi Akila,

We tried this and It still doesn't seem to yield what we're expecting. In the graph above, what parameters did you use for the CV run, so I can try to replicate your graph exactly?

thanks and happy holidays!