Pytrack V_BCKP connection

[Emmanuel Goudot]

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 !

[Emmanuel Goudot]

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.

[jmarcelino]

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

[jmarcelino]

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.

[Charly86]

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 ?

[Charly86]

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

[Redferne]

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?