[ntp:questions] Re: NMEA refclock - PPS not working

dave morgan morgad at eclipse.co.uk
Mon May 15 16:00:26 UTC 2006


On Mon, 15 May 2006 15:41:45 +0100, "R Jenkins" <not at pub.lished> wrote:

>>"dave morgan" <morgad at eclipse.co.uk> wrote in message 
>>news:0kvg62prkbhj8nciotpqqmgqqosq4hotk5 at 4ax.com...
>>On Mon, 15 May 2006 08:34:21 +0100, "R Jenkins" <not at pub.lished> wrote:
>
>>a couple of random thoughts
>
>>a) Have you tried setting ntp.conf to look at the other edge of the PPS 
>>pulse?
>
>>b) Section 4c of the PPS kit install instructions (for PPS kit 2.1.5)
>>caught me out for a couple of weeks. Have you copied both the updated
>>timepps.h and timex.h files so the NTP compile can see them? (I
>>initially only copied one)
>
>>Dave
>>-- 
>>http://www.morgad.no-ip.info/index.html    gpg:0x64B5E037
>>Distributed Proofreaders: http://www.pgdp.net
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>>http://stellar-attraction.com/
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>>questions at lists.ntp.isc.org
>>https://lists.ntp.isc.org/mailman/listinfo/questions
>
>
>Hi Dave,
>
>many thanks for that, I was missing the timex.h file.
>I used just the ppskit-lite patch & only found out about the timepps.h link 
>by chance.
>
>It must have been seriously messing things up as all the jitters etc. 
>immediately reduced to sensible values.
>
>I now get, after around 30 mins running:
>
>ntpq -c peers
>     remote           refid      st t when poll reach   delay   offset 
>jitter
>==============================================================================
>*GPS_NMEA(0)     .GPS.            1 l   17   64  377    0.000   42.046 
>0.062
>-gate.jrw.intra  130.88.200.98    3 u    -   16  377    0.195  200.062 
>0.036
>+sites.urchin.ea 80.253.108.112   3 u   41   64  377   22.420  200.693 
>4.539
>+braindead.mfa.g 195.220.94.163   2 u   54   64  377   88.858  117.665 
>141.465
>
>ntptime
>ntp_gettime() returns code 0 (OK)
>  time c8130f14.e05a1000  Mon, May 15 2006 15:30:44.876, (.876374),
>  maximum error 52983 us, estimated error 0 us
>ntp_adjtime() returns code 0 (OK)
>  modes 0x0 (),
>  offset 47.000 us, frequency -0.276 ppm, interval 4 s,
>  maximum error 52983 us, estimated error 0 us,
>  status 0x107 (PLL,PPSFREQ,PPSTIME,PPSSIGNAL),
>  time constant 2, precision 1.000 us, tolerance 496 ppm,
>  pps frequency -0.276 ppm, stability 1.000 ppm, jitter 1.000 us,
>  intervals 386, jitter exceeded 12, stability exceeded 2, errors 328.
>
>It looks like the PPS input is seeing the wrong edge of the pulse.
>The DCD signal transition is +12 > -12 at the start of the pulse from the 
>GPS, which I thought should be correct.
>
>I will try setting the flag2 option which hopefully will be the final fix!
>
>Thanks again,
>Robert Jenkins.
>
>


After you have been running a couple of days, and
things have stabilized, try this -

----start----
#!/bin/bash
for clockstatsfile in /var/log/ntpstats/clockstats.*
do
  echo -n ${clockstatsfile##*.}
  cut -d, -f 8 <$clockstatsfile | sort -n | uniq -c | tr  [:cntrl:] " "
  echo " "
done
----end----

should give an output like (wrapped by my mailer)

20060507  3 03  32 04   97 05  287 06  464 07  284 08  148 09  25 10
20060508  1 03  23 04  120 05  344 06  470 07  252 08  114 09  15 10
20060509  8 00**33 04  117 05  359 06  457 07  217 08  126 09  22 10
20060510  1 00** 1 03   11 04  112 05  361 06  404 07  308 08  123 09 
 19 10
20060511 10 04  88 05  321 06  435 07  322 08  136 09   28 10
20060512 11 04  84 05  332 06  469 07  294 08  118 09   32 10
20060513  1 03  11 04   77 05  289 06  450 07  318 08  157 09  36 10
20060514  9 04  88 05  357 06  443 07  291 08  121 09   31 10
20060515  5 04  34 05  238 06  255 07  206 08  109 09   24 10

Hopefully there should not be any 00 entries(**) otherwise you might
need a better antenna position (if <3 sats the GPS rx gives *NO* output)

Also don't forget Richard B. Gilbert's post about sorting your config
out and getting a better list of servers to check against.

Your stats should look something like this (small offsets to most other
servers)

david at webserver:~$ ntpq -pn
     remote           refid      st t when poll reach   delay   offset
jitter
==============================================================================
 127.127.1.0     LOCAL(0)        10 l    1   64  377    0.000    0.000
0.001
*127.127.20.0    .GPS.            0 l   11   64  377    0.000    0.006
0.002
-193.25.198.254  195.220.94.163   2 u    8   64  377   21.984    1.758
0.300
+130.88.200.6    193.63.105.18    2 u   65   64  377   27.774    0.270
0.279
-132.146.236.132 193.63.105.18    2 u   61   64  177   28.415   -1.286
1.322
-213.232.95.39   193.10.7.246     2 u   60   64  377   22.013    2.488
0.520
+81.5.136.18     152.78.128.61    3 u   31   64  377   34.771   -0.973
2.089
-83.245.15.97    193.190.230.66   2 u   34   64  377   22.171    2.944
0.554


Dave
-- 
http://www.morgad.no-ip.info/index.html    gpg:0x64B5E037 
Distributed Proofreaders: http://www.pgdp.net
The NTP server pool http://www.pool.ntp.org
http://stellar-attraction.com/



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