[ntp:questions] Garmin GPS 18LVC Setup but questions on best way

George R.Kasica georgek at netwrx1.com
Tue Dec 30 12:10:14 UTC 2008


On Tue, 30 Dec 2008 00:53:00 GMT, Unruh <unruh-spam at physics.ubc.ca>
wrote:

>George R. Kasica <georgek at netwrx1.com> writes:
>
>>On Mon, 29 Dec 2008 12:30:39 +0000, David Woolley
>><david at ex.djwhome.demon.co.uk.invalid> wrote:
>
>>>George R. Kasica wrote:
>>>
>>>> still seing both of the local GPS/PPS entries as false tickers but I
>>>> also see the offsets are huge compared to other clocks...where do I go
>>>> from here to correct this??
>>>
>>>You are probably detecting the wrong edge (wrong polarity) of the second 
>>>pulse.
>>So how in the world do I fix this? 
>
>>Prior to having both NEMA and PPS running at the same time all was
>>working well with just PPS and the shm driver.
>
>What are you using to drive the shm refclock? 
>Of course you can continue to use just pps-- obvioulsy something has gotten
>messed up.

I'm sorry I don't know how to answer that more than  to say the shm
program mentioned in the various docs on line and then the GPS itself
on ttyS0

Here is the script run to set that up and the ntp.conf files with
flags. What changes would I need to make - I'm getting pretty lost
here.:

ntp.conf
========
# LinuxPPS: GPS
server 127.127.20.0 minpoll 4
fudge 127.127.20.0 flag3 1 flag2 0
 
# SHM: PPS filtered mean
server 127.127.28.0 minpoll 4
fudge 127.127.28.0 refid PPS flag3 1

from a small shell script
=========================
# Start shmpps and gpsd daemon
cd /dev
ln -s ttyS0 pps0
ln -s ttyS0 gps0
sleep 2
# Set up shmpps
cd /Linux-Software/shmpps
./shmpps -d /dev/ttyS0 -s -l DCD -u 0 -c
#
# Start up gpsd
/usr/sbin/gpsd -b -n /dev/ttyS0




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