Reading value on GPIO analog mode

Show the link you googled.

JW

The description is a bit blur.

For GPIO with Analog function, the pin structure looks like this: (reference manual)

If you want to know the input voltage level, make sure the pull-up and pull-down are disabled (unless wanting to self test)

Then reading the GPIO Input Register (IDR) to read the pin level respective to datasheet high-low threshold voltage spec.

There is no alternate function for the ADC, ADC has a mux to multiple channels going to selected GPIO as the one above.

I guess that if the pin is not connected and the GPIO is forced as output low or high, the ADC or Analog input can be read/converted. Does it make sense?