Re: [avr-chat] GPS based digital clock

[Juergen Harms]

I have experience with a remotely stabilised digital clock and 
corresponding code - not GPS but DCF based, an DCF being an FM 
transmitter of standard clock time (for me the one in Frankfurt, but 
there are others).

Basic concept: (1) use a normal crystal oscillator (14.xxx Mhz for me), 
(2) add a polynomial correction to correct for the deviation between (a) 
its effective frequency (which nominally may not be precisely a decimal 
fraction of a second and is also subject to variations between 
individual crystals), (3) do all the evident junk to get human readable 
wall-time, do lap-year and daylight saving-time correction (4) receive 
and decode the FM signal from the standard time transmitter, (5) 
whenever you receive a valid value from the FM source, synchronise your 
crystal time with that value (preferably doing this smoothly to avoid 
upsetting the applications that use your time base).

In case you are interested in the corresponding code, say so. If you are 
interested in the DCF time source, most distributors of electronic 
components sell antennas and receivers for a few bucks worth. 
Personally, I have tried two, one distributed by Conrad and one 
distributed by Distrelec and have a clear preference for the latter. You 
can directly feed its output to an input pin of your AVR (I have long 
leads and use a balanced pair for transmission).

Good luck, Juergen