GPIO pullup settings

#1

Hi All
I am using ext0 for waking up Heltec Lora ESP32 board from deepsleep. Works fine if use HIGH pin (GPIO4) for trigger. If i want change it, to LOW pin trigger waking up i use rtc_gpio_pullup_en(GPIO_NUM_4); command, the board keeps wakeup all the time byself. If i put external pullup resistor everythig works fine. If I omit command: rtc_gpio_pullup_en(GPIO_NUM_4); there are not any voltage on pin 4 (pin is isolated btw), if I use command: rtc_gpio_pullup_en(GPIO_NUM_4); there is cca 0.5 V on the pin.

Please help. Is it any other way to put internal pullup or maybe some pins not accepting command?
Thanks

#2

Take a look at the introduction of this function, rtc_ gpio_ hold_ en。

#4

Thanks for respond. Now works. I put pinMode(4,INPUT_PULLUP); under void(setup) and works.
Rgds