Figure2. GPIO input mode with Pull-down resistor Let’s understand theGPIO pinin input mode with external or internal pull-up/pull-down resistor connected, as shown in Figure 1 and Figure 2. It’s a simple circuit in which the floating state is avoided by introducing or activating internal...
Tested it for all GPIOs that can be a DI. Works for all of them but not for GPIO34 ... GPIO39. They work as input but get not pulled up. Same with INPUT_PULLDOWN. These input-only pins don't have PU/PD circuits. OK, thanks for the information. ...