I keep lossing my rtc datetime, when on lipo power.
But on usb, i don’t see any issue.
The schematic of the RAK12002 show the super caps charge from 3V3 (not 3V3_S).
When i have a RAK4631/RAK19001 and the 4631 spents 99% for the time deep sleep, is 3V3 bus still powered and charging the caps?
Not sure why you loose RTC time when running from battery, it should not happen.
3V3 is always on independent whether the RAK4631 is in deep sleep or the supply is from USB or battery.
What is your initialization for the RTC? My default code for the RTC is RAK12002_rtc.cpp
Maybe this setting helps:
rtc.writeToRegister(0x35, 0x00);
rtc.writeToRegister(0x37, 0xB4); // Direct Switching Mode (DSM): when VDD < VBACKUP, switchover occurs from VDD to VBACKUP
I had those initializations in my early projects, but they disappeared at some point.
I have added them back into the current project.
Hopefully that fixes my issues. I will let you know in a couple days.
Thx.
Hello @sspw,
We are having a similar issue with our devices, researching a little bit we noticed that R6 in rak12002 is not populated! (@beegee I would really appreciate your comments here) This is a real big problem, cause the supercaps are being charged via this resistor! Next week we are gonna solder this resistor and also add a Schottky diode in series with it so the supercaps will only distribute power into the RTC and not to the whole VDD power rail when the VDD voltage drops under the supercaps voltage.
We are gonna test with different VDD voltages from an external power supply and see at which voltage the RTC is losing time (first with the module exactly as it comes, then with the hardware changes).
I will post the results here! Regards!
Hello @HeldersX
does your code enable the built-in trickle charger? See RV-3028-C7 datasheet - section: 4.3. TRICKLE CHARGER
Thanks
Felix
Hello @felmue, our code doesn’t enable the trickle charge, I didn’t know about that feature, thank you for the advice! Regardless of that, is really weird that the guys left the pads with the resistor unpopulated but maybe they were thinking about using that trickle charge… We are gonna try that feature also and see how it performs, if it works as it should, then we can use it instead of populate every device with the diode + resistor combo. Thank you very much!
