[ntp:questions] Trimble Resolution SMT on Ubuntu 12.04

G geng_j at yahoo.com
Thu Mar 29 13:59:20 UTC 2012

Hi Ron,

Thanks a lot for your help.

I change my conf as your suggest:
server minpoll 3 maxpoll 3 #ATOM PPS
fudge flag2 0
server mode 17 prefer minpoll 3 maxpoll 3  #NMEA RMC 9600

fudge time2 0.0000
driftfile /var/lib/ntp/ntp.drift


unfortunately, result is not much different. 


----- Original Message -----
From: Ron Frazier (NTP) <timekeepingntplist at c3energy.com>
Cc: "questions at lists.ntp.org" <questions at lists.ntp.org>
Sent: Monday, March 26, 2012 4:19 PM
Subject: Re: [ntp:questions] Trimble Resolution SMT on Ubuntu  12.04

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 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 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.



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 mode 17 prefer       # NMEA RMC/GGA 9600bps
> fudge time2 0.01
> server minpoll 4 maxpoll 4  # PPS ATOM
> fudge 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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