Chad
MuRaT KaRaDeNiZ wrote:
Well, you can try using a temperature measuring device in a pulsed manner and compansate for the thermal deviations and other offsets in software, connect atmega device to pc, use online atomic time servers to get accurate reference clock. can be a nice challange :)RegardsMurat Karadeniz-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf Of Chad O'Neill
Sent: Monday, December 12, 2005 9:30 PM
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] RTC on Mega 8
What would you recommend then if you wanted the accuracy of a normal digital watch?
Chad O'Neill
Ralph Hilton wrote:On Mon, 12 Dec 2005 15:12:52 +1030 you wrote:Hi All, I'm trying to get a RTC going on a Mega 8 using a 32 kc watch crystal as per Atmel app note AVR134. The code works well except that the time gains about 3 seconds per hour. The crystal is a surplus watch crystal that I had and I have no idea of the capacitance load that it requires. Anyone on the list used a watch crystal on an avr and how accurate can you make them for time keeping ? Do I need a 6pf or 10pf crystal? Do I need any extra caps to gnd, not using any at the moment, would a small trimmer help?I would enable the CKOPT fuse which makes added capacitors unnecessary. I would expect a few seconds a day error from a new crystal. If you want something more accurate maxim give away free samples of the DS32KHz oscillator which is good to about a second a week. -- Ralph Hilton http://www.ralphhilton.org C-Meter: http://www.cmeter.org FZAOINT http://www.fzaoint.net ------------------------ Yahoo! Groups Sponsor --------------------~--> Get Bzzzy! (real tools to help you find a job). Welcome to the Sweet Life. http://us.click.yahoo.com/KIlPFB/vlQLAA/TtwFAA/dN_tlB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/AVR-Chat/ <*> To unsubscribe from this group, send an email to: AVR-Chat-unsubscribe@yahoogroups.com <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/