"Q" <....@..> wrote in message
news:4d18cb5a$0$12172$fa0fc...@news.zen.co.uk...
I wonder if someone would be kind enough to help me out a little here. I
have done lots of googleing and found nothing that helps me out with the
issues I'm seeing.
I am trying to reduce the PPS offset & delay (Which seem quite high for
a local device) and stop the NMEA driver from swinging and becoming a
false ticker.
Any ideas please would be great. This is only a personal project, but I
was expecting slightly better results! Below are debug outputs, configs
and some other 'useful' stuff if you could take a look over them and let
me know what I could be doing wrong, or would otherwise benefit from
changing.
Cheers!
GPS;
GPS18x - NMEA outputting GPRMC to serial port.
GPS18x - PPS outputting to Pin 1 of serial port.
For what it's worth, I have been using a GPS18x LVC for quite some time,
and seen no problems. As it happens, this is on a Windows-based stratum-0
clock. Then a few months back, time keeping became erratic. I saw there
was a new firmware out, so I flashed the puck with that firmware and all
was well. For a few more weeks, at least. Then the same happened again
and, as it happened, there was another new firmware out, so I flashed it
again. This time it didn't cure the problem. More careful observation
showed that the NMEA output was being seen as up to a second out compared
to the PPS output. Like you, I have only the one sentence being used, but
I was still at 4800 baud (which should easily allow one sentence per
second, and had for about a year).
The situation now is:
- I don't know why this GPS18x LVC is behaving like this, and why its
behaviour has changed.
- as this system has good links to other reliable servers, I commented out
the NMEA driver, and left in just the ATOM driver:
Old
______________________________________
server 127.127.22.1 minpoll 4
server 127.127.20.1 minpoll 4 prefer mode 33
__________________________________________
New
__________________________________________
server 127.127.22.1 minpoll 4
__________________________________________
and marked one of the reliable servers as "prefer". I wonder if anyone
else has seem similar problems with the GPS18x LVC?
As to PPS offset, I can't measure it accurately here but it appears to be
under a millisecond, and perhaps under 100 microseconds.
Cheers,
David
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