M5Paper EPD power consumption



  • Hello,

    i also made a fisrst compact schema to facilitate understanding

    0_1609362387445_6bedbef9-cc33-48d4-96bd-970bd15532db-image.png

    SYL



  • Hello,

    If the repository is facing the wheel,

    0_1609397793398_abc6142e-f0dd-4827-9167-49a0b347486c-image.png

    "code source" is true, "SCH-name" is false

    0_1609397946546_5e5d7b82-4846-499d-8f3b-096794dee6ba-image.png

    SYL



  • Hello,
    I completed the schema with VUSB_IN, VSYS and OR fonction with D9,D12

    0_1609408092751_1b84713e-842f-4d87-af32-590bbc36dd6f-image.png

    SYL



  • I just received my M5Paper and I can not get a 100% charge? The power consumption also seems high. I am only observing the battery level indicator relative to device use. Is there a problem with the firmware? Is the Wifi function draining the battery prematurely?



  • Hello,
    On mine, the maxi level indicator of charge is 86% corresponding to 4.18V
    I measured USB current with the program "Factory test" and a serial USB device named "UT25".
    The value is 131 mA, without interraction.
    I also wrote personal comments about all GPIOs (in french, my native language):
    0_1609540042308_d0d7e2f2-2754-4c13-bdb0-eac50a0d8423-image.png
    All GPIOs are represented (except non-existent ones : 20, 24, 28, 29, 30, 31)
    SYL



  • @tatar-andrei
    Hello!

    I was wondering if you could provide some reference for how you got into doze mode/wake on touch? I've been trying for a few days now and for the life of me can't seem to make any meaningful progress.



  • You can check other GT9xx drivers like (http://read.pudn.com/downloads710/sourcecode/embedded/2849392/gt9xx.c__.htm).

    I will need to play some more with it. I'll probably post here a link to my repo once I push the code.



  • Hello,
    If you want to measure RTC and zener D11 current, i indicate the PCB resistors positions
    0_1609839826079_87253ca3-b5c9-49a3-a940-755467abbc04-image.png
    SYL



  • Hello,
    As I was saying five days ago,
    "I measured USB current with the program "Factory test" and a serial USB device named "UT25".
    The value is 131 mA, without interraction."
    Since then, I have measured the current according to the different programs :
    0_1609964987251_7f2faa65-cde9-482f-afb7-a5bb3f48ebc1-image.png
    The cause of this excess consumption is IT8951.
    An alternative to this component is the 74HC4094D, 8-stage shift-and-store bus register, used as IO extander.
    A competitor with the same display consumes 65 mA, i measured to.
    SYL



  • Hello,
    Here is Shift Register schema, the brend is Nexperia.
    0_1609978353293_046fa671-5c10-4313-ad80-216963318452-image.png
    SYL



  • @bricox nice work on mapping out the power management system! I've noticed some peculiarities with the charging PMIC (SLM6635, which does not seem to have any english documentation). Specifically, it does not seem to have a proper measuring system set up while charging. Once you connect it to USB power, the indicated battery voltage is actually the charging voltage of the battery, which can be 20-30% higher than the actual (resting) voltage of the battery. This is quite visible if you let the M5Paper with the FactoryTest firmware run out of battery, then connect it to power and head to the factory test screen - the battery indicator will be between 30-50%, and reported battery voltage will be around 3.7-3.8V (which is impossible on a device that was just completely discharged).

    The main problem with this is that the battery cutoff voltage for charging seems to be 4.2V - even though the battery is rated 4.35V officially. You can see this, again, on the Factory firmware, by leaving the unit to charge. Once it hits 4.2V stable, charging is cut to that voltage (and the M5Paper displays ~85% battery left). If you disconnect the charger and reconnect it, charging voltage jumps up to 4.35V, however after some time it stops charging (or switches to trickle charging? Not sure about the inner workings of SLM6635), battery voltage slowly drops to 4.2V, and keeps idling there, requiring another disconnect-reconnect to fully charge it again.

    I was wondering, since there seems to be some rudimentary control over power management, would it be possible to reset the charging circuit, or somehow fake the disconnect-connect cycle on it? Even if it's a software workaround, it would be nice to be able to properly charge to maximum capacity - and also it would allow to collect appropriate readings while charging.

    What I hope for is that the next M5Paper generation gets a better power management solution, even if it's more expensive. Proper PMIC control - especially in low-power applications where one would use an eink screen with an ESP32 for periodic updates - is incredibly important, and right now, by the looks of it, all we have is analog voltage readouts of VBAT, not even the charging/charging complete signals are hooked up (which are arguably important here as well).

    Another thing I thought about regarding power saving - would cutting the power to the EXT ports and the EPD display (via methods disableEPDPower() and disableEXTPower()) result in any savings?

    The cause of this excess consumption is IT8951.
    An alternative to this component is the 74HC4094D, 8-stage shift-and-store bus register, used as IO extander.
    A competitor with the same display consumes 65 mA, i measured to.

    Uhm... Pardon my ignorance but according to my research the IT8591 is a full-blown EPD timing controller, not just a bus register. I don't see how the 74HC4094D would be an alternative (most definitely not a drop-in replacement).