[ntp:questions] fudge time1 for gps-18x-LVC?

David J Taylor david-taylor at blueyonder.delete-this-bit.and-this-part.co.uk.invalid
Sun Feb 7 09:35:23 UTC 2010

"David Lord" <snews at lordynet.org> wrote in message 
news:7t6apeF38bU1 at mid.individual.net...
> Thanks for that page with the scope traces. It suggests I'm in
> right ballpark for fudge time and also confirms same signal
> polarity for pps from my MSF receiver.

... a picture is worth a thousand words ...

> I had single RMC sentence configured way back when I last used
> the 18x-LVC but RMC seemed way too short for a 350ms offset so
> I guessed the 18x-LVC had lost its settings. I'll guess again
> now that it hasn't. I'd switched it off early this morning and
> forgot to check then. Now minicom shows it is still set for RMC.

Yes, he said he had two sentences configured, hence the longer RS-232 
message.  At least he confirms what the delay between PPS and the serial 
message is, and that is different on the GPS18 and GPS18x.  I guess it 
could also change with any firmware update, so worth checking.  It would 
be interesting to have the NMEA driver report what value it finds, perhaps 
as some sort of moving average, once a day.

> When I brought the BR-304 out again in November after failing
> to get any useful timekeeping from it in March/April, I found
> that had reverted back from RMC to its default sentences, but
> that is claimed to have a supercap rather than battery.

Worth checking after a period of inactivity.  Good practice to do so, in 
any case.

> Next experiment is to try type 22 atom driver without type 20
> nmea driver and have the three ntp servers for giving the
> correct second. I'll try with parallel pps first since I was
> unable to get this to work on desktop downstairs and it is
> already wired up for that.
> cheers
> David

I hope someone can confirm which driver reads the parallel port, and 
whether someone can confirm that the NMEA driver can work as a PPS-only 
driver without and serial data (I suspect not).


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