Cannot disable PullUp on GPIO18

[maldus]

Hello everyone,
I'm working on an ESP32S2 and I must read an analog value from GPIO18.
I am successful in reading a correct value from the pin; however, the voltage on the pin never fell below 0.5V (even with an external pulldown resistor), which prompted me to do some experiments.

I started fiddling with an ESP32S2-Devkit-m1 and configured the GPIO18 as a floating input: the result was the same, with the analog level on the pin being 3.3V without anything connected to it. With a pulldown (2KOhm) it falls to about 0.5V.

Is there a special configuration for the GPIO18? I could find nothing specific on the datasheet or other documents. It's the default RX pin for UART1, but I'm not using it in my project.

[MicroController]

https://docs.espressif.com/projects/esp ... pin-layout
GPIO18 is connected to the on-board RGB LED of the devkit, the one that should be labeled "RGB@IO18" on the PCB.