Rockbox Development > Feature Ideas

compensate for drifting RTC

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oayz:
This is surely pretty nice feature. It's been very helpful on early DOS/Windows systems before people figure out s/w to modem NIS centers. Leter with internet RTC correction issue dissapered for good.

Anyway, I think this should be integrated with time setting function
- whenever we correct time by less than 1 hour we shoud be asked to use auto-correction calculated automatically based current, new last correction times.

I wish we would get summer time support as well!

Datman:
Another solution could be a +/- adjust, like in mechanical clocks: everytime the DAP is powered on (or every i.e. 5h if someone keeps it running so many hours...) it calculates the difference between current time&date and the last saved before it was switched off. Then it applies a correction from a value manually written: 0 is the default speed; -100 is -100ppm; +100 is +100ppm (parts per million).

I.e.: 1day~90000seconds; a +50ppm correction would be +4.5seconds in 24hours. If I switch off the DAP (it writes time&date), then I power on 48 hours later it applies +9 seconds.

With a few tries a good correction can be achieved with a simple implementation. Surely it will be much better than nothing!

Llorean:
If that's the case, you don't even need to calculate the time it's been powered off in any fine sense. Every day at midnight add 4.5 seconds. For every midnight that has passed since last power on, add 4.5 seconds. Rather than going adjusting by a percentage or anything like that, just ask the user "how many tenths of a second do I add, per day" or even "how many per week?"

People shouldn't be using these devices for too fine timing in the first place, so pick a granularity that allows a decent amount of precision, and an update schedule (daily, weekly) that means that most drift won't be more than a minute or so no matter how bad the device is. It typically benefits the user if the option is simple and easy to understand, and doesn't require them to do any calculations in their head beyond basic addition/subtraction to figure out the value to set.

Datman:
My Sansa Fuze goes 15 seconds forward in a few (3 or 4?) days! I take the train every day and I have to be aware to look at the phone clock instead of the Fuze, because error can reach 3-4-5 minutes if I don't care to adjust the time for 1 or 2 months.

An old clock has only a screw with +/- symbols. Here there could be a scale +100/-100.

Another solution: now I set the time and click "Memo"; a week or a month later or whenever I want I set another time the time and click "Memo": it computes the correction and apply it now and everytime I power on proportionally to the elapsed time.

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