4. M5Dial generate interrupt from RTC?

M5Dial generate interrupt from RTC?

  • H

    In the diagram of the M5Dial I dont see a connection between the INT pin of the RTC module and the ESP32? Is that correct? Does this also mean i can not generate an interrupt from the RTC clock? That feels weird because i sleep and wake up works through the RTC clock. Any thoughts?
    Regards

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  • C

    The hole board including the ESP32 but except the RTC is switched off when "sleeping" and INT draws Q3 on to connect Vbat to the main power circuit. Short after boot the ESP32 must draw GPIO46 (HOLD) high to hold/keep the board powered on.

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  • H

    Thank you for your reply.
    I assume your conclusion is then also : no wake-up with RTC interrupt?
    Regards

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    C
     1 Reply
  • C

    @happyuser said in M5Dial generate interrupt from RTC?:

    I assume your conclusion is then also : no wake-up with RTC interrupt?

    Uhm no, or yes.... maybe.... depending of how you define "wake-up"🤔 ☺️

    When Q3 goes on the hole board including the ESP32 is switched on so in my book the RTC can "wake up" the hole board. Of course you could say that this is more like "switching on" than "waking up".

    But in fact, when ESP32 is in its "native" deep-sleep the main CPU is also effectively switched off which means it needs to boot completely from scratch when it "wakes up" from that state. Now, it is correct that there are some build in features to test for the reason of the boot and then have the program act on that, but that is actually also possible with the circuit M5Stack built. There is a signal called "wake" connected to GPIO42 which will indicate for the ESP32 whether it was started by the push button (S1) or by the INT signal from the RTC chip.

    I can only speculate in why M5Stack has chosen not to use the build in ESP32 RTC/deep sleep functionality but here is two reasons:

    • If the board as a hole needs to have a very low power consumption in (deep)sleep mode it is not enough to just have ESP sleep there are other chips or circuits that may still consume "a lot" just by having Vcc applied. So you need the MOSFET switches any way for a "good sleeping" board and
    • the BM8563 seems to consume less than the ESP32 built-in RTC about ~2-3µA vs 10µA
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