RTC Battery Backup

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User avatar
Coco Xia
Posts: 75
Joined: Wed Aug 02, 2017 8:36 am

Sat Apr 28, 2018 2:10 am

untitled86 wrote:
Fri Apr 20, 2018 3:46 pm
I don’t have a picture now of the battery connection, but I can supply one later.

We verified polarity by powering the device up without the battery and using a multimeter. Also the panda’s backup battery V+ pad has a mark above it, so we always had that wired correctly.

We’re using the auto power-on feature in the BIOS and the LattePanda simply refuses to power up sometimes. This happens very rarely, one out of 500 times. But only with the 3V backup battery connected.

I’m working with an experianced electrical engineer on this in a professional setting. We automated surprise resets to test our LattePanda based product and that’s how we discovered this problem.

If the panda refuses to turn on we can hold the power button down and it will reset and boot.

We’ve bought about 30 LattePandas so far. It’d be great if this could be fixed. I hope it’s a bios Power-On logic problem not a hardware problem.

Not sure where the problem is, would you have any other alternative solution?Can we add a button to control the connection of the RTC battery?that's what in my mind, but i don't know if is feasible. Any idea? :)

User avatar
untitled86
Posts: 24
Joined: Thu May 04, 2017 4:30 am

Mon May 07, 2018 9:30 pm

LattePanda wrote:
Fri Apr 20, 2018 4:03 am
untitled86 wrote:
Thu Apr 19, 2018 4:52 pm
@Coco Xia

We're having this problem as well. The voltage isn't reversed. Any other possible causes?
LattePanda wrote:
Thu Feb 01, 2018 2:59 am


Hi, please make sure you've not reversed the positive and negative . :)
Would you mind to describe your case in details? Or some photos? How about the frequency of these similar situation?
We still haven't resolved this problem, but we believe we know the cause. There's a setting in the BIOS, "RTC Lock" that enables or disables writing to the RTC's NVRAM. If this NVRAM gets corrupted (because power disappears while writing for example) it can cause the system to fail to boot. Removing the clock will reset this.

Is there a way for us to reset the NVRAM other than removing the battery? ...If we sign an NDA can we get the schematic for the LattePanda board? We're buying ~10-20 of these a month now.

User avatar
untitled86
Posts: 24
Joined: Thu May 04, 2017 4:30 am

Mon May 07, 2018 9:33 pm

Coco Xia wrote:
Sat Apr 28, 2018 2:10 am
untitled86 wrote:
Fri Apr 20, 2018 3:46 pm
I don’t have a picture now of the battery connection, but I can supply one later.

We verified polarity by powering the device up without the battery and using a multimeter. Also the panda’s backup battery V+ pad has a mark above it, so we always had that wired correctly.

We’re using the auto power-on feature in the BIOS and the LattePanda simply refuses to power up sometimes. This happens very rarely, one out of 500 times. But only with the 3V backup battery connected.

I’m working with an experianced electrical engineer on this in a professional setting. We automated surprise resets to test our LattePanda based product and that’s how we discovered this problem.

If the panda refuses to turn on we can hold the power button down and it will reset and boot.

We’ve bought about 30 LattePandas so far. It’d be great if this could be fixed. I hope it’s a bios Power-On logic problem not a hardware problem.

Not sure where the problem is, would you have any other alternative solution?Can we add a button to control the connection of the RTC battery?that's what in my mind, but i don't know if is feasible. Any idea? :)
Thanks, we've considered adding an analog switch/transistor to control the RTC. But we want to understand the problem so we can prevent it. Now we believe the RTC's NVRAM is getting corrupt. That would match our symptom.

User avatar
thangta
Posts: 1
Joined: Tue Nov 17, 2020 1:57 am

Wed Nov 25, 2020 1:38 am

HI, Did you fix this error? I also have the same problem

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