[ntp:questions] PPS signal from Garmin GPS 18x LVC

David Taylor david-taylor at blueyonder.co.uk.invalid
Mon Dec 30 11:17:01 UTC 2013

On 29/12/2013 23:51, Adrian P wrote:
> Now I am wondering if there is any other way to see if the PPS signal
> is used or not... maybe with some debugging?
> Adrian


Does the ppstest work?  That shows whether the hardware is connecting 
properly, and that PPS support is present.  Yes, I see from your earlier 
post that it does work.  But try ppstest as ppswatch - see how close the 
the second edge you are.

If so, what are the relevant lines in your ntp.conf?

You should be seeing one line of output from ntpq -pn for each of the 
configured servers.  However, checking on my FreeBSD system shows that 
the NMEA driver can produce PPS sync directly, without having to add the 
atom driver.

I see that you have:

server mode 1 minpoll 4 maxpoll 4 prefer
fudge flag1 1 flag2 0 flag3 1 refid PPS

I have:

server mode 0 minpoll 4 maxpoll 4 prefer
fudge flag1 1 flag3 1 refid PPS

I'm not sure whether it matters which sentence you choose to process - 
it seems that I'm using mode 0 - $GPMRC.  I would see whether altering 
flag3 to 0 makes any difference, as there was a discussion about the 
polarity of that flag.

Just a few things which you can try easily.

Yes, ntpd can be run with debugging, but that's rather outside my expertise.
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