[lug] Time sync w/GPS or radio

Jason Vallery jason at vallery.net
Sun May 18 18:20:55 MDT 2008

If you really need that level of precision the GPS 18 actually has a version
that can do PPS.

GPS 18 LVC — has bare wire for connection to a variety of applications; can
output data in NMEA 0183 format (industry standard) or proprietary Garmin
format; provides a pulse-per-second logic-level output with a rising edge
aligned to within 1 microsecond of UTC time.


On Sun, May 18, 2008 at 5:10 PM, David L. Anselmi <anselmi at anselmi.us>

> Jason Vallery wrote:
>> Hi All,
>> I'm a bit late to this thread, but I was working on a separate project
> As long as we're posting late...
> [...]
>> If you look at the NMEA spec the data stream contains the UTC time.
>> It seems like it would be pretty trivial to write up a shell script
>> that monitors the serial interface and sets the clock based on the
>> incoming data stream.
> You probably can set the clock from that and for most uses that might be
> fine.  But you won't get the accuracy or clock discipline that NTP can get
> from a PPS signal, right?
> (And we all know sysadmins love disciplining their clocks...)
> Dave
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Jason Vallery
jason at vallery.net

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