ESP32CAM RXD2 pin stuck to 3.3V (not by pullup)

[dammuw1]

Hello,

on my ESP32CAM board (two different boards tested), the GPIO16 pin (RXD2) is stuck to high.
22 kOhm resistor connected to ground (to make voltage divider with the on board 10 kOhm pullup).
After SW was flashed the pin shows ~2.2 V.
After I perform a reset (reset-button)
the measured voltage raises to 3.18 V (3.3 pin shows 3.20V)

I stripped my SW down to empty setup()/loop() functions (using Arduino IDE)
Even if I use pinMode(16, INPUT);
in setup() the behavior is the same.

Any idea? Any special configuration to be done for that board? Thank you for any kind of feedback/idea.

Uwe

[ESP_LJH]

Why you connect a pull-down at GPIO16? GPIO16 is used by PSRAM. And I want to confirm that IO16 is only high at boot-up or it still could be low after boot-up process?

[dammuw1]

Without pulldown, the voltage would be 3.2 V due to the pullup resistor in the ESP32CAM board.
In my case it has an additional purpose, I setup a voltage divider for the 5V output voltage of the Arduino RS232 TxD I want to receive using the ESP32 RxD2.

Do you know, if PSRAM is enabled by Arduino automatically? Is there a way beside:
GPIO_ENABLE_REG to configure the GPIO16 as output? (I checked, that GPIO_ENABLE_REG.16==0 -> I expect the pin should be floating, instead of driving it to 3.2 V)

[dammuw1]

Found some answers:
https://www.reddit.com/r/esp32/comments ... /?sort=top
-> same issue, but no solution

https://rntlab.com/question/espcam-gpio ... available/
-> similar issue, but seems to be due to 10k pullup, rather than sourcing high the GPIO16 (as observed by me)

https://preview.redd.it/yv050peu22p21.p ... 2c447fa9eb
-> schematic

PSRAM.CS# PIN is indeed connected to GPIO16, this is an input for the PSRAM (chipselect). which would not drive the pin to high... Maybe the two boards I use are broken...