Hi,
I am currently working with an nRF52 board connected to the AD5941 EVAL-AD5941ELCZ through SPI.
-
SPI communication is verified (Chip ID can be read correctly).
-
I am using the Amperometry application mode.
What I observe:
-
When I set
Vzero = 800 mV, the SE node reads ~800 mV. -
When I set
Vzero = 1100 mV, the SE node reads ~1100 mV.
So the SE pin clearly follows the Vzero setting as expected.
However, the RE pin does not behave as expected:
-
With
Vzero = 800 mVandVbias = 0 mV, I expect RE ≈ 800 mV. -
With
Vzero = 800 mVandVbias = 200 mV, I expect RE ≈ 1000 mV.
But in both cases, RE does not show these expected values at all.
In summary:
-
SE output is correct (tracks Vzero).
-
RE output is incorrect (does not track Vbias).
This makes me suspect that either there is an issue with the switch matrix configuration, or I may have overlooked some minor but crucial detail.
I will share my code configuration as well in case something is missing there.
Please advise on what I might be missing and how I can properly drive/observe RE output voltage.
Attached is the code for reference.
Thank you very much for your help.
void AD5940Sensor::start(int16_t Vbias, uint32_t pulseLenforCHRONO, uint8_t sensorIndex)
{
configurationInit(Vbias, pulseLenforCHRONO);
sensorIDX = sensorIndex;
switch (_SensorMethod)
{
case Amperometry:
AppAMPCtrl(AMPCTRL_START, 0);
break;
case ChronoAmperometry:
AppCHRONOAMPCtrl(CHRONOAMPCTRL_PULSETEST, 0);
break;
case Impedance:
AppIMPCtrl(IMPCTRL_START, 0);
break;
default:
break;
}
}
void AD5940Sensor::configurationInit(int16_t Vbias, uint32_t PulseLen)
{
/*
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
*/
// switch (cfg)
switch (_SensorMethod)
{
case Amperometry:
AppAMPCfg.bParaChanged = bFALSE;
// AppAMPCfg.SeqStartAddr = 0;
// AppAMPCfg.MaxSeqLen = 0;
AppAMPCfg.SeqStartAddrCal = 0;
AppAMPCfg.MaxSeqLenCal = 0;
// AppAMPCfg.FifoThresh = 5;
AppAMPCfg.SysClkFreq = 16000000.0;
// AppAMPCfg.WuptClkFreq = 32000.0;
AppAMPCfg.AdcClkFreq = 16000000.0;
AppAMPCfg.NumOfData = -1;
AppAMPCfg.RcalVal = 10000.0; /* RCAL = 10kOhm */
AppAMPCfg.PwrMod = AFEPWR_LP;
AppAMPCfg.AMPInited = bFALSE;
AppAMPCfg.StopRequired = bFALSE;
/* LPTIA Configure */
AppAMPCfg.ExtRtia = bFALSE; /* Set to true if using external RTIA */
// AppAMPCfg.LptiaRtiaSel = LPTIARTIA_4K;
AppAMPCfg.LpTiaRf = LPTIARF_1M; /* Configure LPF resistor */
// AppAMPCfg.LpTiaRl = LPTIARLOAD_100R;
AppAMPCfg.ReDoRtiaCal = bTRUE;
AppAMPCfg.RtiaCalValue = {0, 0};
AppAMPCfg.ExtRtiaVal = 0;
/* ADC Configure*/
AppAMPCfg.ADCSinc3Osr = ADCSINC3OSR_4;
AppAMPCfg.ADCSinc2Osr = ADCSINC2OSR_22;
AppAMPCfg.DataFifoSrc = FIFOSRC_SINC2NOTCH;
AppAMPCfg.ADCRefVolt = 1.8162; /* Measure voltage on ADCRefVolt pin and enter here*/
LOG_INF("LFOSC = %.2f Hz", (double)LFOSCFreq);
AppAMPCfg.WuptClkFreq = LFOSCFreq;
AppAMPCfg.SeqStartAddr = 0;
AppAMPCfg.MaxSeqLen = 512;
AppAMPCfg.NumOfData = -1; /* Never stop until you stop it manually by AppAMPCtrl() function */
AppAMPCfg.LpTiaRl = LPTIARLOAD_10R;
AppAMPCfg.LptiaRtiaSel = LPTIARTIA_3K; /* COnfigure RTIA */
/* user define parameters */
AppAMPCfg.AmpODR = 0.5f; /* Sample time in seconds. I.e. every 5 seconds make a measurement */
AppAMPCfg.FifoThresh = 4; /* Number of points for FIFO */
/* Sensor related parameters */
AppAMPCfg.ADCPgaGain = ADCPGA_1P5;
AppAMPCfg.SensorBias = Vbias; /* Vbias Sets voltage between RE0 and SE0 */
AppAMPCfg.Vzero = 800; /* Sets voltage on SE0 and LPTIA */
// AppAMPInit((uint32_t *)pBuffer, bufferSize);
AppAMPInit(AppBuff[0], APPBUFF_SIZE);
break;
