Lime2 RTC battery

[splite]

Hello,

I can not find if the LiPo battery of the Lime2 can be use as RTC backup battery to save date & time ?

What are the solution ?

Thanks,
Florian

[LubOlimex]

Li-Po battery keeps the whole board fully powered, including date and time. It is connected to IPSOUT line of the AXP209 which is the "main battery".

Now the AXP has a separate 3V coin battery option only for the date and time. It is something like second backup. This supply goes to pin #30 of the AXP209 PMU. In the schematic it is called "AXP_BACKUP" and goes to separate pads named "BACKUP". Read more about this battery option in AXP209's datasheet here: http://dl.linux-sunxi.org/AXP/AXP209_Datasheet_v1.0en.pdf search for "Backup Battery".

It is worth mentioning that the main power supply goes to the ACIN line, which is the "Adapter input". And finally powering via USB has own power line called "VBUS".

"Adapter input", "VBUS", "Main battery", and "Backup battery" have different properties. That is why powering the board via USB is not recommended even if you have externally powered USB - the AXP209 wouldn't draw more 500/900mA from it; while if using the power jack it would allow consumption of up to 2500mA.

[splite]

Hey Lub,

Thanks for these good advice. I did not quite well understood if I can use the LiPo battery to save the clock.

In my use case, I have only the LiPo battery and this is not saving the clock. Is there any way to save it this way ?

Thanks
Florian

[LubOlimex]

How do you check the time?

How is the Li-Po not saving the time, if the board doesn't shutdown (since the Li-Po is keep it fully powered)?

What image you you using?

If you want to preserve time between reboots you would find this thread helpful: https://www.olimex.com/forum/index.php?topic=3896.0