Hi Geng,
I don't know if this will help or not, but the following things came to
mind. I am running Windows at the moment, but Linux should be similar.
I plan to try all this in Ubuntu eventually.
When I was using NMEA only data, I had to have a bigger fudge factor,
like this:
fudge 127.127.20.5 time2 0.3710 refid GPS1
# use WITHOUT PPS
However, when I started using PPS, I found that the fudge factor was
messing things up, so now I use this:
fudge 127.127.20.5 time2 0.0000 refid GPS1
# use WITH PPS
Note that I stuck the fudge factor in there for readability. However,
its value is 0.
The other thing that occurred is that your clock may be too far out from
gps time to begin with. Try shutting down NTPD. Note, if you compiled
NTP yourself, the startup and shutdown scripts may not be in the right
places. I think the command is:
sudo /etc/init.d ntp stop
Then run this command to sync your clock with the NIST server in New
York. If you're not in the US, substitute another server name.
ntpdate -b nist1-ny.ustiming.org
Now your clock should be very close to NIST or UTC.
Now, restart NTPD.
sudo /etc/init.d ntp start
Wait a few minutes and run ntpq -p to see what's happening.
Also, make sure NTPD is reading the correct config file and that you
don't have two of them around or something.
Finally, I'd recommend putting minpoll 4 maxpoll 4 on your NMEA line to
match your PPS line. I'm using a value of 3 on mine, which polls every
8 seconds.
Sincerely,
Ron
On 3/26/2012 12:06 PM, G wrote:
I use Trimble Resolution SMT to sync time for a Ubuntu 12.04 server (kernel
3.2.0).
Trimble send NMEA to /dev/ttyUSB1(9600 8N1) on Ubuntu server
PPS signal connect ACK pin on /dev/parport0 . Ubuntu load Linux-PPS module(
PPS_parport clear_wait=0) to create PPS device /dev/pps0
I use verify the /dev/pps0 using rising edge by "ppstest /dev/pps0"
--------------------------------------------------------------------------------------------
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1332775909.500413150, sequence: 249302 - clear 0.000000000,
sequence: 0
source 0 - assert 1332775910.500456132, sequence: 249303 - clear 0.000000000,
sequence: 0
source 0 - assert 1332775911.500499213, sequence: 249304 - clear 0.000000000,
sequence: 0
-----------------------------------------------------------------------------------------------
To verify the NMEA message , I link /dev/ttyUSB1 to /dev/gps1
-----------------------------------------------------------------------------------------------
#cat /dev/gps1
$GPRMC,153343.000,A,4529.904930,N,07343.904831,W,0.241,325,260312,,,A*6F
$GPGGA,153344.000,4529.905010,N,07343.904879,W,1,3,3.17,12.368,M,-32.087,M,,*5E
---------------------------------------------------------------------------------------------------
I create the /etc/ntp.conf:
-------------------------------------------------------------------------
server 127.127.20.1 mode 17 prefer # NMEA RMC/GGA 9600bps
fudge 127.127.20.1 time2 0.01
server 127.127.22.0 minpoll 4 maxpoll 4 # PPS ATOM
fudge 127.127.22.0 flag2 0 flag3 1
driftfile /var/lib/ntp/ntp.drift
------------------------------------------------------------------------------
after ntpd run 48hours, ntpq -p:
remote refid st t when poll reach delay offset jitter
==============================================================================
xGPS_NMEA(1) .GPS. 0 l 44 64 377 0.000 -214.54 25.464
xPPS(0) .PPS. 0 l 11 16 377 0.000 -174.60 4.981
I have no idea why I got this result . what do I miss for config? by the way ,
I compile ntpd from source , not using ntpd from Ubuntu.
Thanks for your time to read my question. give me some light please.
regards,
geng
--
(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such. I don't always see new messages very quickly. If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)
Ron Frazier
timekeepingdude AT c3energy.com
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