[ntp:questions] PPS problem

Mike George mgeorge at tuffmail.us
Sun Apr 6 15:02:33 UTC 2014


Arthur:

I am also using GPIO PPS and I saw what you describe when using
different options for NMEA flag3.
It sounds like you have flag 3 set to 0 in your NMEA config.
It defaults to 0 if you don't set it.
      0 uses ntpd clock discipline
      1 uses kernel clock discipline

I'm not sure what the practical differences are between the two
options but one of the effects I notices were PPSFREQ & PPSTIME
status bits were set on when kernel discipline was enabled.

I've never seen PPSSIGNAL set on my systems either.
I am using both GPIO PPS and serial line discipline and neither type
display PPSSIGNAL in the status.
Maybe it is used by a different driver?

Mike George

On 4/6/2014 04:18, Simchaev Arthur-BAS071 wrote:
> 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
>> http://lists.ntp.org/listinfo/questions
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