It is possible to turn on the VBIAS and at the same time use this pint as a reference in negative AIN to perform measurement referenced to VDDreg/2?
Just like that
pADI_ADC0->CON = (pADI_ADC0->CON & ~ADC0CON_ADCCP_MSK & ~ADC0CON_ADCCN_MSK) | ADC0CON_ADCCP_AIN10 | ADC0CON_ADCCN_AIN11;
/* ON Vbias */ pADI_ADC0->ADCCFG = ADCCFG_PINSEL_AIN11;
Not sure if it can work well due to the limited drive capability. You can have a try.
However I don't suggest to use this way. Because we always hope that the reference has good drift and precision performance. Obviously the voltage get from Vbias cannot match this point.
barryzhang thanks for the replay. Initialy I wanted to do this ratiometricly in pH measurement (bias pH voltage and reference to AIN) but now I have changed the design.