STM32 controlled PI detector

[cristiano.sar]

Now I have another doubt, as my Stm32 is powered this way (VDD = power supply GND and VSS = power supply -3.3v), to give the preamp signal to the ADC input, I need to create a centered reference of 1.65v, should this 1.65 be positive or negative relative do circuit GND, so the ADC can read it properly?

Thanks.

[eduardo1979]

The value must be negative (-1.65V) with respect to GND.

[cristiano.sar]

The value must be negative (-1.65V) with respect to GND.

Thank you!