5. Cannot start running on bat while com.x is connected

Cannot start running on bat while com.x is connected

  • T

    Hi there,

    I've made a following setup:

    Core2 - (removed factory battery)
    Com.x Nb-IoT module
    Com.x GPS module
    Bottom2

    When I power it up using usbc on core2 everything works perfectly. When I disconnect usbc power source it continues to work on battery (which is in bottom2) and this is also fine.

    The problem is when I switch it off and try to start it only on battery. It starts only for a fraction of a second then turns off. I tried the same thing with both com.x modules disconnected and in that case it powers up normally.

    Anyone knows maybe why it cannot start up on battery but can run on battery once it has been started using usbc power and how to circumvent this situation?

    0

  • Hello @Test471

    what is the behavior with only one of the two modules stacked?

    What happens (w/ both modules stacked) after it turns off?

    • Does it stay off? Maybe the battery needs to be charged a little more?
    • Does it try to start again, eg. boot loop? Maybe the battery cannot handle the initial current for the core and both modules?

    There is a note on both COM.X module description pages saying that with M5Core2 one is supposed to use an external DC power supply: The equipment needs to use external DC for power supply. Not sure though if that means it is not supposed to run from battery or if it only means when not using a battery it needs to be powered from external DC power instead of USBC power.

    Edit: I don't own the COMX.GPS module so I cannot try the exact same constellation, but as soon as I connect two COMX modules (eg. NB-IoT and LoraWAN) my M5Core2 only starts for a short period and then shuts down. For me that happens when powered for USBC or battery.

    I think what might be happening is that the 5 V boost IC shuts down due to a too high inrush current. When running from battery (or USB for that matter) the battery (or USB) voltage gets reduced to 3.3 V (in the AXP192) and then is boosted back up to 5 V (through the SY7088) which then needs to power everything on the 5 V line.

    Thanks
    Felix

    0
    T
     1 Reply
  • T

    @felmue Seems like you're right. In the meantime I charged the battery to almost 4V and now it can start on battery almost every time I try. I guess when battery is 100% full it will work fine.

    And yes, when startup fails it just stays off without boot loop or anything like that. LCD and green LED inside just blink for a sec and it is off. Just like there is not enough power.

    I just tried running on usb without the battery (removed bottom2) and everything works fine. Both nbiot modem and gps are performing as expected.

    Yes, I know about this thing with connecting external 5V/12V directly to the module but there I have another problem:

    When I run it on usb/battery and call M5.shutdown() function (or press the button) everything shuts down (including com.x modules) which is something that I expect.

    When I run it on external 12V and call M5.shutdown() or press the button then only Core2 is shut down. Other com.x components are still running and I don't know how to switch them off.

    Also, if I plug out the 12V then com.x components are off but Core2 stays running on battery and I am also not sure how to handle this. That is why powering via USB is perfect solution because when I plug the usb out then Axp.isOnAC() is false so I can call shutdown() method which will switch everything off.

    0

  • Hello @Test471

    I don't see anything in the COMX module schematic which would allow the DCDC converter in the module to be turned off programmatically. The DCDC converter is on when external DC power is applied and off when DC power is disconnected.

    However there is a power off AT command AT+CPOWD for the SIM7020 module. Have a look at its datasheet linked here under related link.

    Thanks
    Felix

    0
  • T

    Thank you very much for your help. I will give it a try.

    0