> Le 24 juil. 2019 à 11:19, William Unruh <un...@invalid.ca> a écrit : >> >> The hardware under consideration can time the pulse arrivals more >> precisely than the interrupt delivery time, thanks to special hardware.
That tickled a grey cell. There was/is a timing product family bc635/637 time and frequency processors sold by Microsemi which can timestamp a PPS input event to 100ns resolution. Various OS drivers are available, but no ntp refclock driver AFAIK. > > Does that hardware read the local clock of the computer, or its own > internal clock, which then means you have to also figure out what the > relation is between that hardware clock and the system time. > It also means that you have to be careful of termination resistances in > the lines from the gps to that hardware and drive power from the clock. > Remember the "faster than light" neutrinos, which cam down to a bad > fibre optics connection from the gps to the underground detector, making > the underground clock sightly late, making it look like neutrinos got > there faster than than they did. > > The application of the corrections should all get handled in an > ntp driver for the gps unit, which can > apply the corrections and deliver the corrected readings to ntpd. ntpd > has about 50 different refclock drivers and one might well cover your > case. Otherwise one might need to be written. > > >> >> Once that has been set up (in the future), the next problem becomes >> applying the higher precision offset to the time source data input to >> the ntp algorithms. >> >> At a higher abstraction level this means telling ntp that "at >> hhmmss.xxxxxxxxx (local clock), a time stamp of hhmmss.yyyyyyyyy >> arrived from this hardware time source". > > OK, that should work. The main problem is that usually that correction > comes long (seconds) after the actual pulse itself as I understand. > >> >> >> >> Enjoy >> >> Jakob > > _______________________________________________ > questions mailing list > questions@lists.ntp.org > http://lists.ntp.org/listinfo/questions « What’s the point? » J.C. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
