[ntp:questions] Odd offset for PPS DCD w/ Garmin GPS 18x LVC

unruh unruh at wormhole.physics.ubc.ca
Thu Mar 24 18:55:59 UTC 2011


On 2011-03-24, lellis <larry.ellis at gmail.com> wrote:
> On Mar 23, 11:21?pm, Dave Hart <daveh... at gmail.com> wrote:
>> On Thu, Mar 24, 2011 at 04:17 UTC, Dave Hart <daveh... at gmail.com> wrote:
>> > 4.2.7p24 came out in April 2009
>>
>> Correction: 4.2.7p24 came out 13 April 2010.
>>
>> > Nothing between p23 and p24 jumps out at me as likely related. I
>> > wonder if this cset from October 2010 (first included in 4.2.5p237-RC)
>>
>> I need coffee. ?4.2.5p237-RC came out 26 October 2009.
>>
>> Cheers,
>> Dave Hart
>
> I can only reaffirm my willingness to try any build provided.
>
> I would suppose this is somehow related to the Garmin's weird NMEA
> message timing with respect to the PPS output.  I don't remember the
> details, and I also know that things changed from the original GPS 18
> model to the improved GPS 18x.  And then, there's 3.20 firmware vs
> other firmware to bring into the mix.

It delayed the nmea messages to just more than a second after the
associated PPS pulse ( ie the nmea sentence came more than a second
after the time it was reporting). This make the system seem to be out by
a second. It is a bug. 

>
> I still have the older GPS 18 somewhere.   I'll try it to see if
> there's a difference.
>




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