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Topic: What is causing my time inaccuracy? (Read 2 times) previous topic - next topic


Woah, I'm sorry.  It would have been more helpful to explain your self.

In any case I reread the relevant section of wiring.c and it appears that the fractions of MS are taken care of.  My mistake.


Jan 20, 2011, 03:26 pm Last Edit: Jan 20, 2011, 03:27 pm by retrolefty Reason: 1
I get 10 seconds a day accuracy out of a Uno and better than 2 seconds a day out of my Duemilanoves  with crystals

sore point........

Well now you have a solution don't you? Just load your older 328 board, that has a crystal, with the new and improved and fixed opto-dewanko bootloader and presto a uno board that keeps time better.

Call it your Uno2009 and use your real Uno as a blink the led demo board.  ;)



Now if the Uno used the same port in Linux, they could be interchangeable......  

Honestly though, would real crystals break the budget on the Uno ?, mine has one crystal on the 8U2 serial USB chip, why not on both ?

I've no issues with resonators on a low end stuff, but surely a real genuine made in Italy Arduino Uno isn't low end ?  

They are still flogging 2009 knockoffs on Ebay that have crystals.


It might be worth to consider a RTC e.g. from the datalog shield - http://www.ladyada.net/make/logshield/index.html - although I never have investigated the accuracy my gut feeling says its less than 10 seconds a day.

If you need higher accuracy you must consider syncing with a timeserver using the NTP protocol (e.g. every hour)
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


Thank you all for the responses.  It's an Uno board that I just purchased, so it's probably the latest one.  I was just so surprised that the accuracy was THAT bad using the chip.  

I already ordered the Sparkfun RTC, our choices are very limited here in Singapore as far as local suppliers which we don't need to wait 2 weeks for.  The local companies seem to have 95% Sparkfun products :/

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