STM32F429ZI reference voltage
In the datasheet page 434 it describes how you can set a reference voltage from 1.8V but not less. If you want the DAC to have full resolution between 0-1V that's just not possible. However you would get pretty acurate readings anyway.



If you want to change the resolution with a new reference voltage you use a voltage divider to set the voltage (1.8V-3.3V). If you set it to say 1.8V then a reading of 1.8V in 12 bit resolution reads 4095.



Since this is the lowest you can go a reading of 1V with this resolution would give you the digital number 2275 giving you a resolution of 0-2275. Alternately you could amplify the signal you are measuring to 1.8-3.3V.