OK, I use the two GPSDOs method because I can set the PPS position but the cable is useful and only one GPSDO (or any other stable PPS source) is enough.
On Sat, Dec 8, 2012 at 6:53 PM, Don Latham <[email protected]> wrote: > I use a tee connection and terminated 100 foot (33 m )piece of RG58 coax > for a known delay to the stop pulse. > Don L > > Azelio Boriani > > Yes, this is a good test: to evaluate how your preferred uP can perform > > as > > a time interval counter, you can hook two GPDSOs' PPS to it and see the > > result. The best would be to have at hand also a real TIC (HP53132A, > > PM6681, SR620 or similar) and compare. > > > > On Sat, Dec 8, 2012 at 4:28 AM, Bob Camp <[email protected]> wrote: > > > >> Hi > >> > >> A lot depends on exactly what the interrupt structure is. It may also > >> depend on the phase of the cpu clock relative to the pps signal. > >> What's > >> reasonably sure is that there is indeed some offset between the two > >> where > >> the answer is indeed "ft's" random. Another thing to check - how wide > >> is > >> the random region? > >> > >> Bob > >> > >> On Dec 7, 2012, at 9:19 PM, Chris Albertson > >> <[email protected]> > >> wrote: > >> > >> > One more test to try. Connect one PPS signal to both GPIO ports and > >> see > >> > how close to zero offset you get. It would likely be random which > >> gets > >> > read first. > >> > > >> > > >> > On Wed, Dec 5, 2012 at 5:37 AM, Gabs Ricalde <[email protected]> > >> wrote: > >> > > >> >> Hi everyone, > >> >> > >> >> As Tom suggested, I redid the test with less than 1 ft. of wire > >> from the > >> >> PPS output to the GPIO without any logic gates or line receivers. > >> Same > >> >> result, > >> >> the SKG25A1 was 2 microseconds ahead of the 58534A. Without any > >> other > >> way > >> >> of > >> >> testing, I would probably trust the output of the timing receiver > >> more > >> >> than the SkyNav module. Anyway the SkyNav board is an inexpensive > >> unit > >> and > >> >> I wouldn't mind setting an offset in ntpd. > >> >> > >> >> I don't have a scope yet, and a low jitter PPS GPIO is the closest > >> thing I > >> >> have > >> >> to a TIC. > >> >> > >> >> _______________________________________________ > >> >> 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. > >> >> > >> > > >> > > >> > > >> > -- > >> > > >> > Chris Albertson > >> > Redondo Beach, California > >> > _______________________________________________ > >> > 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. > >> > >> > >> _______________________________________________ > >> 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. > >> > > _______________________________________________ > > 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. > > > > > -- > "Neither the voice of authority nor the weight of reason and argument > are as significant as experiment, for thence comes quiet to the mind." > De Erroribus Medicorum, R. Bacon, 13th century. > "If you don't know what it is, don't poke it." > Ghost in the Shell > > > Dr. Don Latham AJ7LL > Six Mile Systems LLP > 17850 Six Mile Road > POB 134 > Huson, MT, 59846 > VOX 406-626-4304 > www.lightningforensics.com > www.sixmilesystems.com > > > > _______________________________________________ > 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. > _______________________________________________ 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.
