[ntp:questions] Fwd: Re: NetBSD GPS/PPS using 4.2.6p3

Rob nomail at example.com
Thu Aug 25 15:34:48 UTC 2011


unruh <unruh at wormhole.physics.ubc.ca> wrote:
>> any sense to me. Perhaps you meant the NMEA sentence used
>> needed to be within .5 sec but again that doesn't make a
>> lot of sense in practice as all three different gps units
>> I've used each have large variations in NMEA time so
>> require both fudge factor and increase in the range of
>> values that will be accepted.
>
> Nope, I meant that system time should be within .4 sec. That will not
> matter if you use gpsd since that should accurately get the time of the
> pps pulse from the nmea of the gps unit (assuming it is not broken like
> some of the garmin 18x are).

What happens with gpsd is completely unrelated to what happens when
you use ntpd's own NMEA and PPS support.

When you have experienced that you should be within .4 sec before PPS
works when using gpsd, you should not project that onto ntpd and its
PPS support.  The .4 sec check is within gpsd.




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