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Precision Clock Mk II - Date portion only showing a random mess
Willemde20 Posted: 30 Oct 2023, 01:20 PM
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Hello,

Precision Clock Mk II has been working great for years now. But after yesterdays DST ending it stopped working right. After a reboot it only shows the time and a mess for the date.

Right now it shows 20-7-Hp-HH and then the correct time. Any tips on how to trouble shoot this issue?

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mit Posted: 1 Nov 2023, 10:00 PM
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yeah whatever

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Hi, sorry for the slow response.

There are a few things that can cause the display to mess up like that. It is strange that it would happen specifically after the DST switch though.

Does it have a full GPS fix when it's showing this?

Is it using the same power supply it's always been using? Could that have become damaged in some way? Electrical noise could cause distortion on the serial data. It's worth trying it with a different power supply if you have one.

Is this at all brightness levels? Again the power supply stability may be affected by the current draw, which will be less if you cover the light sensor.

What's the room temperature? Depending on when the clock was made, the oscillator may not be calibrated, or it may be just on the edge of the tolerance and if the room is suddenly colder than usual (or a lot warmer than usual) it could affect it. You could try warming the ATtiny chip and seeing if that has an effect.

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parrotycheck Posted: 6 Nov 2023, 05:49 PM
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I've just brought mine out of storage and plugged it in, I'm getting

20HH-22-09 95:22:PX.XX (where X.XX is an incremental second counter)

Last night it was flipping between the above format and the correct expected date format.

Power supply is from one of my PC monitors, I'll try a more robust one as soon as I can. Temperature wise it's not exactly warm in here, but it's not freezing either - I tried placing it in the PC's exhaust which is reasonably toasty but it didn't help.

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Willemde20 Posted: 7 Nov 2023, 09:27 AM
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Hey, thanks for the responses! I Power cycled it again and it seems to be working again as usual.

GPS fix seems to be harder somehow its in the same position as it has been since December last year.

And yea i have noticed the clock spitting random stuff when it gets cold in the room. but that wasn't the case this time since it just was stuck on that random output.

But it is working now so all good.

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mit Posted: 7 Nov 2023, 11:18 PM
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yeah whatever

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There are a few other threads here relating to the oscillator calibration, see here and here, which also links to a couple more. For the last few years I've been calibrating the oscillators before shipping them, so this issue has almost completely disappeared, but it's not impossible I've made mistakes during the calibration process.

See also this thread where the power supply was the culprit, and it only manifested when on max brightness.

Another situation that can lead to scrambled data on the date is during first power-up of the GPS module, it can sometimes misinterpret the serial data when the module does not yet have the date available, but this always goes away when it gets a GPS fix.

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