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.
