setting up STM32H757 with ACD1 measuring at 3.3v

[RAtki.2]

Hi 

i am using a STM32H757 with ACD1 measuring a voltage around 1.8v and adc2 at 3.3v, But my adc1 value is 1488 for 12 bit adc. Vref+ is at 3.3v and Vref- at ground. how do set the parameters to measure 3.3V adc? as i seem to be getting the wrong value. 

[Tesla DeLorean]

>>as i seem to be getting the wrong value. 

Of what?

1488 is more indicative of 1.19V, unless +VREF is 5V

What do you get when you measure 3.3V?

What is the source of these voltages?

[RAtki.2]

+Vref is set to 3.3v

-vref is gnd

adc 2 is measuring the supply

adc1 is measuring a voltage 20v which stepped down by resistors to 1.8v