Pytrack V_BCKP connection



  • Is V_BCKP (pin 6 of Quectel L76 GPS) connected to something on Pytrack ?
    This pin, usually connected to very small battery (7µA conso) would enable standby mode when pytrack is in deep_sleep mode (where I guess VCC is off), or when pytrack is off.
    Standby mode would enable 5s or 15s TTFF instead of 30s. This would save a lot of uptime !
    0_1499497761849_upload-6270004a-f958-4c60-bda5-851406923fe8



  • Reading this up and down a couple of times. But still cannot figure out if V_BCKP is connected to the L76 GPS or not? Trying to use go_to_sleep(gps=True) but it still takes 30+ seconds to get a GPS fix after waking up. Straight up, do I need to solder a bridge on the unpopulated component or not?



  • As today I think it's done in pytrack.lib, looking at go_to_sleep seems to set a PIC output, so my guess is it's connected to PIC PC7?

        def go_to_sleep(self, gps=True):
            # enable or disable back-up power to the GPS receiver
            if gps:
                self.set_bits_in_memory(PORTC_ADDR, 1 << 7)
            else:
                self.mask_bits_in_memory(PORTC_ADDR, ~(1 << 7))
    

    Tested and confirmed go_to_sleep(gps=True) fix takes 1/2 seconds from wake from deep sleep and when go_to_sleep(gps=False) is used fix takes much longer, may be same as first fix
    Good to know



  • Hi Guys,
    I'm facing the same issue, would be very helpfull having some schematics for this kind of questions.

    Anyway did one of you succeed to enable V_BCKP to increase fix time on wake up from deep sleep?

    May be stupid question, connecting V_BCKP to a I/O pin, then put this I/O High before deep sleep could to the trick ?



  • Well it's not connected to the PIC16, it seems to end on one pad of an unpopulated component - the pad NOT marked with +. The other side of that component (which is marked +) then connects to 3v3_Sensors.

    I wonder what was supposed to be there - diode? - and/or why it was removed.

    0_1499635373306_IMG_2559.JPG



  • @Emmanuel-Goudot
    I think I see V_BCKP connected but not sure where to, possibly all the way to PIC16?

    0_1499624142244_IMG_2557.JPG



  • It seems after testing that L76 VCC and V_BCKP are not powered during deep_sleep.
    So backup state is not possible as it is.

    As 3v3_Pymodule is still on, would connecting V_BCKP to 3v3_Pymodule wouldn't be possible ?
    That would make consumption of 18µA+7µA=25µA in deep sleep.


 

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