How the built-in RTC works

[Gfast2]

Hi ESP-IDF,

Thanks for your supporting again. I do know most of my question can find their answers from ESP-IDF source code, or from ESP32 Datasheets. But it take times for me to get more and more "Woooooha" from my own search in a very effective professional way. Please be patient.

RTC.png (13.83 KiB) Viewed 26922 times

1. I saw the dev-board from sparkfun as example has the 32.768kHz quarz for RTC, in ESP32's Datasheet RTC are mentioned many times, too. But they are more to "Sleep Mode" related. So, If I just wanna ESP32 keeps its time when the power is removed, as in kolban's tutorial implementated with a DS1307 breakout shows. How should I wire the backup battery? and what kind of effort in code should I investate? (Is that means, if I do need to restart ESP32 instead of deep-sleep, should I wake-up ESP32 when main power is reavailable and do a manual "esp_restart()"?). Is there some small snippet about this topic?

2. Why pin15 and pin16 which are connected to the 32.768kHz quarz can be posted as GPIOs? Is that means, this quarz is only be used when in deep-sleep mode? what kind of use case for both pins should I consider to avoid? (I have experienced bad enough issues with GPIO0 and GPIO2 for ethernet and sd Card interface. It takes me literally more then two weeks to bugshooting. Fun, learned much but still painful)

Cheers

Gfast2

[urbanze]

1-) I have not yet used the RTC in esp32, but in the 66 it worked besides reset's via software, that allowed to work with sleep and etc. However, what I have already done and can assure you is to use the ULP to make a simple watch or even the complete calendar. Remembering that the ULP in Deep Sleep consumes ~ 150uA (or less if using certain methods). One cool thing about working with ULP and Deep Sleep is the ability to "hold" the state of a pin so it will not be interfered between Sleep and Wake-up

2) Nothing xD