Hi Bob S, I have noticed skipped 1PPS on the Adafruit GPS also. Some days are clean, other days miss a few samples. I have not explained it yet. I plan to run two GPS boards and two counters to narrow down the cause.
In any event, IMHO, a GPSDO should not go crazy if glitches like this occur. I don't think it should go into holdover for one missed sample, or even a few missed samples. But then you need to define what holdover is. I mean, by some definition a GPSDO is in "holdover" between every second. I do not think there is any standard. Just conventions: some documented, some not. It's attention to a dozen little details like this that separate a quick hack GPSDO from a quality one. You'll also face a number of design issues at startup, and coming out of holdover. Lastly, you get to choose between it being an ideal time standard vs. an ideal frequency standard. /tvb p.s. Please fix your address book. The correct email for the list is [email protected] ----- Original Message ----- From: Bob Stewart To: [email protected] Sent: Tuesday, April 22, 2014 6:03 PM Subject: GPSDO and holdover I hope I haven't asked this before, but is there a standard way of deciding to go into holdover mode? I'm still wrapping up code for this Adafruit, and as I've posted before: every now and then it skips a PPS. I'm trying to decide whether to allow a free pass (if not followed by another skip within some timeframe) or to immediately stop processing any further PPS pulses until I decide based on some criteria that they're reliable. Bob - AE6RV _______________________________________________ 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.
