A C wrote:
On 9/9/2012 15:41, E-Mail Sent to this address will be added to the
BlackLists wrote:
A C wrote:
Has anyone seen a system with GPS/PPS have its system
time ramp/slew ahead by over a second requiring a step
correction?
Prefer the PPS source?
GPS time is usually only second relative without the PPS,
and will sometimes drift around a lot within the second
on non timing GPSes.
I have GPS chips on embedded systems that the serial sentence
always seems to wander around 20ms to 50ms.
NTP doesn't let me prefer the PPS source (ATOM). I'm forced to prefer
some other source and let PPS activate on its own.
When atom driver was working reliably I had both type-20
and type-22 drivers specified, the type-20 NMEA gave the
"second" and PPS sync was from type-22 atom.
Because of the wander of the nmea value it was also
required that I had "tos mindist 0.5" and used a large
fudge time for the nmea. Both required values depended on
the particular make and firmware revision of the GPS unit.
David
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