Problem with GPSD refclock
hmurray at megapathdsl.net
Thu Jan 26 18:46:20 UTC 2017
richw at richw.org said:
> When I first wired up a GPS in 2009 for use as an NTP refclock, my
> understanding was that USB-based devices (including "serial port" PCIe cards
> which really used USB technology under the hood) were simply not capable of
> the exact timing necessary to handle a PPS signal from a GPS unit.
I've never seen a PCI serial card that used USB. (But there is a lot of the
world I haven't seen.)
It would require 2 chips rather than one: PCI-USB and USB-Serial vs
PPS over USB adds roughly 1 ms of noise/jitter. It works, just not as well
as a real serial port.
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