[ntp:questions] PPS problem

Simchaev Arthur-BAS071 BAS071 at motorolasolutions.com
Sun Apr 6 08:18:24 UTC 2014


Hi David 

I have the following system :
uname -a
Linux am335x-evm 3.2.0-4.08 #5 Wed Mar 12 15:07:28 IST 2014 armv7l GNU/Linux

And pps is existed in the kernel , when I run ppstest /dev/pps0 , I see the pps clock grown . Also ntpd shows that the server is PPS "o".
But I am confuse why I still don't see PPSFREQ,PPSTIME,PPSSIGNAL status . How I can be sure that my clock is synchronized to the PPS ?

Regards
Arthur

-----Original Message-----
From: questions-bounces+bas071=motorolasolutions.com at lists.ntp.org [mailto:questions-bounces+bas071=motorolasolutions.com at lists.ntp.org] On Behalf Of David Lord
Sent: Thursday, April 03, 2014 1:48 PM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] PPS problem

Simchaev Arthur-BAS071 wrote:
> Hi Guys
> Thank you to your assistance . Seems is working now .
> I see that NMEA chosen as PPS peer server :
> 
> remote           refid      st t when poll reach   delay   offset  jitter
> ==============================================================================
> oGPS_NMEA(0)     .GPS.            0 l   12   16  377    0.010   -0.030   0.031. 
> 
> But please clarify the following :
> 1) Can I sure that is update the system clock in PPS resolution
> 2) Why I still doesn't see PPSFREQ,PPSTIME,PPSSIGNAL , when I run ntptime .
> My output is following :
> ntptime
> ntp_gettime() returns code 0 (OK)
>   time d6e78fed.18c23fa0  Thu, Apr  3 2014  7:44:45.096, (.096714581),
>   maximum error 3888 us, estimated error 474 us, TAI offset 0
> ntp_adjtime() returns code 0 (OK)
>   modes 0x0 (),
>   offset 50.880 us, frequency -26.830 ppm, interval 1 s,
>   maximum error 3888 us, estimated error 474 us,
>   status 0x2001 (PLL,NANO),
>   time constant 4, precision 0.001 us, tolerance 500 ppm. 

Hi

Above looks as if you are synced to NMEA rather than PPS.

What cpu, operating system and version are you using?

For NetBSD-6/i386 I have to use a custom kernel to enable PPS.

When I tried with Ubuntu-10/i386 I needed to install a pps package.


David

> root at am335x-evm:/var/lib/ntp# ntpq -c as
> 
> ind assid status  conf reach auth condition  last_event cnt 
> ===========================================================
>   1 65397  976a   yes   yes  none  pps.peer    sys_peer  6
> root at am335x-evm:/var/lib/ntp# ntpq -c "rv 65397"
> associd=65397 status=976a conf, reach, sel_pps.peer, 6 events, 
> sys_peer, srcadr=GPS_NMEA(0), srcport=123, dstadr=127.0.0.1, 
> dstport=123, leap=00, stratum=0, precision=-20, rootdelay=0.000, 
> rootdisp=0.000, refid=GPS,
> reftime=d6e79065.fffb1778  Thu, Apr  3 2014  7:46:45.999, 
> rec=d6e79066.73ee526e  Thu, Apr  3 2014  7:46:46.452, reach=377, 
> unreach=0, hmode=3, pmode=4, hpoll=4, ppoll=4, headway=0, flash=00 ok, 
> keyid=0, offset=0.054, delay=0.000, dispersion=0.262, jitter=0.031,
> filtdelay=     0.00    0.00    0.00    0.00    0.00    0.00    0.00    0.00,
> filtoffset=    0.05    0.06    0.06    0.06    0.07    0.06    0.07    0.05,
> filtdisp=      0.03    0.27    0.51    0.75    0.99    1.23    1.47    1.71
> 
> 3) Since I can attach only one GPS to the board ntp.conf is following :
> 
> tos orphan 6
> driftfile /var/lib/ntp/ntp.drift
>  
> 
> server 127.127.20.0 minpoll 4  iburst #NMEA Server
> fudge   127.127.20.0 flag1 1 flag2 0 time2 0.500
> 
> Regards
> Arthur
>  
> 
> -----Original Message-----
> From: questions-bounces+bas071=motorolasolutions.com at lists.ntp.org 
> [mailto:questions-bounces+bas071=motorolasolutions.com at lists.ntp.org] 
> On Behalf Of David Lord
> Sent: Wednesday, April 02, 2014 11:25 PM
> To: questions at lists.ntp.org
> Subject: Re: PPS problem
> 
> 
> David Lord wrote:
> 
> .....
> 
> 
>> I currently use a "Sure" gps, ntp-dev-4.2.7p433 on NetBSD-6
>>
>> I have a few significant differences in my ntp.conf
>>
>> #################
>> tos orphan 10
> 
> A few more comments
> 
> tos orphan 10 # is to replace your three lines:
> server 127.127.1.0 #lo server
> fudge 127.127.1.0 stratum 7
> restrict 127.127.1.0 noquery nomodify notrap
> 
>> tos mindist 0.4  # allows pps to kick in
>>     ^^^^^^^^^^^
> 
>> server 127.127.20.2 mode 18
> 
> You can use this as prefer peer:
> server 127.127.20.0 prefer
> 
>> fudge  127.127.20.2 stratum 7 time2 0.407 flag1 0 refid GPSb
> 
> Required value for time2 will depend on your GPS model and firmware version.
> 
>> server 127.127.22.2 minpoll 4 maxpoll 4 server 127.127.22.2 flag2 0
>> flag3 1 refid PPSb server -4 <ntp0.mydomain> server -4 <ntp1.myisp> 
>> minpoll 8 maxpoll 10 iburst prefer
> 
> 
> For what it's worth the last entry in my
> /var/log/ntp-stat.20140402:
> 
> Wed Apr  2 17:36:00 GMT 2014
>       remote   refid st t poll reach   delay   offset  jitter
> ============================================================
> -GPS_NMEA(2) .GPSb.  7 l   64  377    0.000   -1.940   8.828
> oPPS(2)      .PPSb.  0 l   16  377    0.000    0.000   0.004
> +ns0.lordyne 81.187  3 u   64  377    1.363   -0.175   0.202
>   ns2.lordyne 192.16  2 u   64  377    0.498   -0.237   0.613
> +ns1.lordyne 81.187  3 u   64  377    0.577    0.007   0.703
> +ns3.lordyne 81.187  3 u   64  377    0.849   -0.486   0.690
> *ntp1.xxxxxx 195.66  2 u  256  377   19.589   -0.943   0.403
> 
> associd=0 status=011d leap_none, sync_pps, 1 event, kern,
> pll offset:            -0.000317
> pll frequency:         -35.8115
> maximum error:         0.406
> estimated error:       3e-06
> kernel status:         pll ppsfreq ppstime ppssignal nano
> pll time constant:     4
> precision:             1e-06
> frequency tolerance:   495.911
> pps frequency:         -35.8115
> pps stability:         0.00480652
> pps jitter:            0.002
> calibration interval   256
> calibration cycles:    6087
> jitter exceeded:       7635
> stability exceeded:    0
> calibration errors:    20
> 
> ntp_adjtime() returns code 0 (OK)
>    modes 0x0 (),
>    offset -0.317 us, frequency -35.812 ppm, interval 256 s,
>    maximum error 406000 us, estimated error 3 us,
>    status 0x2107 (PLL,PPSFREQ,PPSTIME,PPSSIGNAL,NANO),
>    time constant 4, precision 0.001 us, tolerance 496 ppm,
>    pps frequency -35.812 ppm, stability 0.005 ppm,
>    jitter 1.500 us, intervals 6087, jitter exceeded 7635,
>    stability exceeded 0, errors 20.
> 
> 
> David
> 
> _______________________________________________
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> questions at lists.ntp.org
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