Why the unusually high "LOW" voltage when pressing NodeMCU ESP-32s boot button?
According to the datasheet page 15 ("Strapping Pins" section): https://www.espressif.com/sites/default/files/documentation/esp32-s2_datasheet_en.pdf

"GPIO0, GPIO45 and GPIO46 are connected to the chip’s internal pull-up/pull-down during the chip reset.
Consequently, if they are unconnected or the connected external circuit is high-impedance, the internal weak
pull-up/pull-down will determine the default input level of these strapping pins"

Table 3 shows GPIO0 is tied-up to the default pull-up during system reset.
Table 9 shows the default pull-up resistor value is typically 45kOhm.
So in theory you should measure about 0.156V at the pin when pressing the button.

In your case measuring 1.33V on GPIO0 means the equivalent pull-up resistance would be around 700 Ohm, more like if the ESP is actively driving it rather than being passive pulling.


Can you boot the ESP normally then measure the voltage on that pin when the button is pressed and released?
Can you now turn the power off, press the button while monitor the GPIO0 voltage and turn the board back on?
Any differences between these 2 operations?