chipKIT® Development Platform

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Battery backup for Uno32

Created Sat, 29 Dec 2012 18:53:12 +0000 by helpme


Sat, 29 Dec 2012 18:53:12 +0000


I need to maintain the wall clock time through a power outage.

I currently use an external RTC, with battery, which uses I2C and is currently a headache to get it to jibe with the rest of the components.

I noticed in the ChipKit Uno32 Reference Manual that pin 6 (VIN) can be used to power the board. And the ChipKit Uno32 has an on chip RTCC.

I noticed that the PIC32 Pinguino has implemented a battery backup solution:

Li-Ion/Li-Poly rechargable battery power supply option with built-in on board charger. When a battery is attached to the JST connector, it is automatically charged and kept in this state until the other power source (USB or external adapter) is removed. The switch-over is automatic - no jumpers, no switches!

Does anyone know of or used a similar battery backup solution for the ChipKit? Also, it would be nice if the fact that battery is being used to power the system is apparent to the software, as the only thing useful to accomplish on battery power would be to maintain the wall clock time. Bonus Question: What would be the ball park period that the system could operate on battery backup? The reason I ask is that outages of seconds to minutes would be expected, outages of hours would be rare but nice to be handled, outages of days would need human interaction with the system and resetting the wall clock time would be a comparatively minor issue.

Thanks in advance,



Sat, 29 Dec 2012 20:03:27 +0000

Do you know the chipKIT Uno32 has already a built-in Real Time Clock?

You only need to solder a 32.768 kHz quartz.

Learn more and download the library from :arrow: chipKIT Built-In Real Time Clock

Enjoy ;)


Sat, 29 Dec 2012 21:33:47 +0000

Yes, I know the ChipKit Uno32 has a RTCC, but it is useless if it does not maintain the wall clock time through a power outage, the whole point of the topic.

Thanks for the pointer to the library.



Fri, 04 Jan 2013 05:58:10 +0000

I use this. Just attach to the 5V pin.


Fri, 04 Jan 2013 13:50:51 +0000

I usually recommend the SparkFun LiPower shield:


It has everything you need (except the battery - you need to supply your own), including a fuel gauge chip to monitor the charge on the battery.


Fri, 04 Jan 2013 14:09:53 +0000

Isn't there something like :arrow: this possible for the Uno32?

The Teensy 3 is powered by a coin cell in order to keep the RTC running.