How is "blackpill" ADC analog voltage supplied?

[derek-eder]

I am interested in the ADC analog voltage supplies - specifically VDDA and Vref+

Is it possible to isolate these and supply the analog voltage from an external supply? One developer, Martin Loren*, says he "removes a component" (capacitor ?) on the blackpill board and wires a "shunt" to supply an external Vref+ from board pin PA2 but I can't find any blackpill board schematics or PCB layout to get more details.

STM provided a seperate analog supply to the ADC for a very good reason and I would like to be able to use them in the Blackpill or some future iteration.

Many thanks!

Derek Eder

• https://www.martinloren.com/hs40x-diy-oscilloscopes/

[WeActStudio]

STM32F411CEU6 Only VDDA, no VREF.
You can use one ADC specifically to read the voltage from the external reference source, and then another ADC to sample what you need, and compare the two.