Hi Jim: I've made similar clocks using PIC micro controllers where the input is the 10 MHz from the frequency standard. http://www.prc68.com/I/PRC68COM.shtml#07092006
There's a subtle problem that has to do with if an interrupt occurs during a 3 cycle long instruction or a 2 cycle long instruction. This can cause erratic behavior if not properly accounted for. The 1 PPS from your clock should be spot on all the time, not off by a few hundred nano seconds. Have Fun, Brooke Clarke http://www.prc68.com/P/Prod.html Products I make and sell http://www.prc68.com/Alpha.shtml All my web pages listed based on html name http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Web Cam Jim Palfreyman wrote: > This discussion has come at an interesting time. > > I've hooked up an LPRO-101 from ebay to an AVR micro-controller - basically > using it to clock the processor directly. > > I've written code so the AVR is a clock and I've been comparing my clock's 1 > PPS to the GPS. > > Over a few minutes it hops back and forward a few hundred nsec. All quite > acceptable given the clock speed. > > When I come back after a few hours it will suddenly be 10-20 usec slow. I > did see it jump over a few seconds from 200nsec to 17 usec. > > At first I put this down to interference because it coincide with me > switching off a light. So I put the whole lot into a metal box, shorter > wires and tried again. > > It still has jumps but this time it is *gaining*. > > Until this post started I'd assumed it was maybe my code and was about to > dive in and check it. > > Could these crystal "jumps" account for my issues? > > Regards, > > Jim _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
