Lime2 RTC battery question???

Started by jamesmustain, February 17, 2021, 06:39:47 AM

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jamesmustain

Hi there, I can't find if the LiPo battery of the Lime2 can be use as RTC backup battery to save date & time?
Any help? Thanks!

LubOlimex

The Li-Po battery keeps the whole board alive and operational! Including the RTC.

There is built-in charger, so the transition external power -> battery and vice versa is seamless (as long as the battery has some charge).

There is an option to add an extra battery for only the RTC! The RTC back-up, is lead out to BACKUP pin holes near edge of board (no connector by default), you can attach 3V to it it to keep the RTC.

For best back-up it is probably to have both batteries present.

My advice is to check the AXP209 datasheet and find more info about Backup battery (BACKUP) and main battery (IPSOUT):

https://linux-sunxi.org/images/8/89/AXP209_Datasheet_v1.0en.pdf

If you are not happy with the built in battery options you can place external RTC module. It will not fit inside the metal frame, since the UBS ports are lead out of the box. It will be attached outside of the frame. I would recommend MOD-RTC2, it uses I2C:

https://www.olimex.com/Products/Modules/Time/MOD-RTC2/open-source-hardware
Technical support and documentation manager at Olimex