[time-nuts] garmin 18 lvc versus garmin 18x lvc with pps & ntp

Hal Murray hmurray at megapathdsl.net
Wed May 20 19:35:30 UTC 2009


folkert at vanheusden.com said:
> Could not find any help anywhere on the web so you guys are my last
> hope. I have 2 computers running a linux PPS enabled kernel and ntp.
> One of the two has a garmin 18 lvc, one has a garmin 18x lvc. 

You will probably get better help with NTP related issues from the ntp people.

There is a mailing list at:
  https://lists.ntp.org/mailman/listinfo/questions
It's gatewayed to usenet:comp.protocols.time.ntp

The NMEA driver is interesting.  First, it gets the time from the serial 
port.  If that looks reasonable, it fixes up the bottom bits of the timestamp 
with the data from the PPS info.

The timing on the serial port for the Garmin 18x units is pretty bad.  (The 
-18 non-x was pretty good.)  I'll have to look closely at the source code to 
see what that "reasonable" filter does.



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