I am using the EVAL-AD5940ELCZU. I running the AD5940 impedance example. I have changed some of the parameters from the function void AD5940ImpedanceStructInit(void) in the file AD5940Main.c and others from AppIMPCfg_Type in Impedance.c file.
It measures reasonably well for high impedance values at low frequencies as I guess the calibration resistor is of the same order, but when I tried to measure low impedances (e.g 100 to 2kOhm) I am getting really bad values.
I can see changing ADCSINC3OSR to 4 helps a little bit . Then I read on another Q&A to use the SINC2 and oversampling so I can get more cycles of the signal. The problem comes when I tried to select DFTSRC as SINC2NOTCH. It stops printing data and it seems to not enter in the "if(AD5940_GetMCUIntFlag())" shwon below. When I use SINC3 or AVG as a source data for the DFT works fine, but when I try SINC2NOTCH or ADCRAW doesnt work.
I do also have the EVAL-ADuCM355 which are using similar logic and it works fine in this instance.
Is there any code missing in the AD5940 that stops doing a DFT of the data coming our from the filtering SINC2? How can I solve this issue for the EVAL AD5940-ELCZ?