[ntp:questions] Re: NMEA refclock questions: baud-rate and PPS

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk.invalid
Sat Jan 28 15:22:41 UTC 2006


David J Taylor wrote:
> Folks, I'm thinking of adding my new Garmin GPS 18 LVC just to see how
> well it might function with serial input alone, so I have some
> questions.
> With the NMEA refclock driver (type 20):
>
> - is it possible to select the baud rate without re-compiling or must
> it be 4800?  I would have thought that having the higher baud rate
> might perhaps improve jitter.
>
> - is a PPS signal actually required, or will the driver function with
> just the serial input (I realise that accuracy will be much worse
> without the PPS, but his is just for testing).
>
> - is it possible to use NTP just to observe a refclock, without
> actually syncing time with it?
>
> Thanks,
> David

OK, I did some testing!  I'd still like to know if you can select the COM 
port and baud rate without recompiling.

- yes, it works without the PPS input, although the jitter seems as high 
as 5 msec

- set stratum to 10 to stop it syncing and just observe - would that work?

David 





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