Lime2 battery backuped RTC

[panda84]

I have the same exact question as in this thread:
https://www.olimex.com/forum/index.php?topic=5386.0
but instead of the A20 SOM I'm interested in the A20-OLinuXino-LIME2.

The Lipo battery would be an acceptable solution if I could put the battery inside the Lime2 metallic case. Unfortunately the connector is headed towards the outside of the case, not towards the inside, so that doesn't seem to be an option.

Powering only the builtin RTC would be the best option, but I can't seem to find the AXP_BACKUP signal in the GPIO connectors PIN table of the A20-OLinuXino-LIME2 manual.

Is there any way to battery backup only the builtin RTC in the Lime2?

Thanks you very much for any help provided.
Diego

[LubOlimex]

Hello Diego,

The AXP209 pin that keeps the RTC alive is LDO1. A20-OLinuXino-LIME2 doesn't have LDO1 pin exposed at all. From the A20 boards that we manufacture so far only A20-SOM has this pin exposed.

You can use external RTC module to keep the RTC alive. We have a project for MOD-RTC and A20 boards (over I2C interface). The code and details are located here: https://github.com/OLIMEX/OLINUXINO/blob/master/SOFTWARE/A20/A20-OLinuXino-Micro%20with%20MOD-RTC/README_RTC_A20.txt

Alternatively, consider de-soldering the connector that bothers you and placing a connector with the orientation that you want (or solder the battery directly to the pads left after the removal of the plastic connector).

Edit October 2019: the infomation above is no longer correct. Refer to the following forum post for more info about the backup pin in LIME2 design: https://www.olimex.com/forum/index.php?topic=7232.msg27533#msg27533

Best regards,
Lub/OLIMEX

[panda84]

Thank you very much LubOlimex for the kind reply.

(or solder the battery directly to the pads left after the removal of the plastic connector).

Can you please kindly elaborate? Do you mean LDO1 pad is actually accessible under one of the plastic connectors on the Lime2?

Thanks

[LubOlimex]

Do you mean LDO1 pad is actually accessible under one of the plastic connectors on the Lime2?

No. Not at all. LDO1 pad is not led out from the AXP209. Its ball is not routed anywhere. My comment was not related to the LDO1. It was related to the LiPo battery connector orientation that bothered you, the following part of your comment "The Lipo battery would be an acceptable solution if I could put the battery inside the Lime2 metallic case. Unfortunately the connector is headed towards the outside of the case, not towards the inside, so that doesn't seem to be an option."[/s]

Edit October 2019: the infomation above is no longer correct. Refer to the following forum post for more info about the backup pin in LIME2 design: https://www.olimex.com/forum/index.php?topic=7232.msg27533#msg27533

[panda84]

Do you mean LDO1 pad is actually accessible under one of the plastic connectors on the Lime2?

No. Not at all. LDO1 pad is not led out from the AXP209. Its ball is not routed anywhere. My comment was not related to the LDO1. It was related to the LiPo battery connector orientation that bothered you, the following part of your comment "The Lipo battery would be an acceptable solution if I could put the battery inside the Lime2 metallic case. Unfortunately the connector is headed towards the outside of the case, not towards the inside, so that doesn't seem to be an option."

Ah, that all makes sense now, the first part of your reply was about the second part of my initial post, and the second part of your reply was about the first part of my initial post.

Thank you very much again,
Diego