[ntp:questions] Re: Garmin GPS 18 firmware update -> 200ms offset

Terje Mathisen terje.mathisen at hda.hydro.com
Fri Nov 25 07:05:31 UTC 2005


Tapio Sokura wrote:
> Roman Mäder wrote:
> 
>> configured for comparison (ntpq 4.2.0, Solaris 8). Yesterday i updated
>> its
>> firmware from 2.40 to 2.80 and now suddenly the offset is around -190ms,
> 
> 
> Have you checked the settings of the unit, that the PPS pulse width is
> ok and that the PPS pulse is enabled? Those settings might have changed
> for some reason in the firmware update.

Or the sign of the pulse might have been inverted!

~200 ms is a common length of a timing pulse, but OTOH those pulses
generated by GPSs usually maintain pretty stable widths as well, i.e. if
this was the problem you should have seen a consistent value like
198.567 ms +/- 0.005 ms.

Run your Garmin config sw again, as Tapio wrote it is much more likely
that the default configuration after a new firmware load is to disable
PPS altogether!

Terje

-- 
- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"




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