Hello.
On an ESP32-POE-ISO-EA-16MB board.
On the ESP32 GPIO0 and GPIO15 are strapping pins. Could I have problems if I install an external 10k pull up resistor in both of them? I want to use them as inputs through an optocoupler and I want to install external resistors.
Greetings and thank you
GPIO15 is not a strapping pin.
GPIO0 is strapping pin and if pulled up at reset the board won't enter download mode. Meaning you can't reprogram the board. Notice that GPIO0 has internal pull up, not sure why you need external one.
Overall I would recommend NOT using GPIO0 but another GPI or GPIO pin instead. GPIO0 is a very special pin and I wouldn't recommend changing its pull ups or pull downs. Since you need input, I'd recommend one of the pins that are only inputs like GPI35 or GPI36.
You need to read the ESP32 datasheet and any notes about GPIO0 and GPIO15.
https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf