[ntp:questions] PPS and PLL frequency

Neil Green ncguk at hotmail.co.uk
Fri Dec 19 12:57:16 UTC 2014


Hello all,

I'm using a Raspberry Pi B+ with a U-Blox Max7q GPS to drive a stratum 1 NTP server. At the moment I'm at the point of following instructions and learning as much as I can, and would like to know, based on the info below, if there's anything I should do with things like PPS and/or PLL frequency and, if so, what:

associd=0 status=041d leap_none, sync_uhf_radio, 1 event, kern,
version="ntpd 4.2.7p483 at 1.2483-o Thu Dec 11 09:04:07 UTC 2014 (1)",
processor="armv6l", system="Linux/3.12.34", leap=00, stratum=1,
precision=-19, rootdelay=0.000, rootdisp=1.630, refid=NMEA,
reftime=d83e9df1.d85b58fa  Fri, Dec 19 2014 12:52:01.845,
clock=d83e9e1c.128dbc16  Fri, Dec 19 2014 12:52:44.072, peer=22016, tc=6,
mintc=3, offset=0.000317, frequency=-29.344, sys_jitter=0.001907,
clk_jitter=0.001, clk_wander=0.009, tai=35, leapsec=201207010000,
expire=201506280000
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
o127.127.20.0    .NMEA.           0 l   43   64  377    0.000    0.000   0.002
-87.124.126.49   195.66.241.2     2 u   57   64  377   29.529    7.658   5.192
+130.88.200.6    130.88.212.143   3 u   65   64  377   17.293    2.666   1.470
+217.114.59.3    158.43.192.66    2 u   52   64  377   15.972    4.004   1.486
*158.43.128.66   193.67.79.202    2 u   58   64  377   10.612    1.694   1.242
ntp_gettime() returns code 0 (OK)
  time d83e9e1c.471b6914  Fri, Dec 19 2014 12:52:44.277, (.277762324),
  maximum error 22500 us, estimated error 0 us, TAI offset 35
ntp_adjtime() returns code 0 (OK)
  modes 0x0 (),
  offset 0.000 us, frequency -29.344 ppm, interval 256 s,
  maximum error 22500 us, estimated error 0 us,
  status 0x2107 (PLL,PPSFREQ,PPSTIME,PPSSIGNAL,NANO),
  time constant 6, precision 0.001 us, tolerance 500 ppm,
  pps frequency -29.344 ppm, stability 0.016 ppm, jitter 0.806 us,
  intervals 38, jitter exceeded 7, stability exceeded 0, errors 0.
associd=0 status=0000 no events, clk_unspec,
device="NMEA GPS Clock",
timecode="$GPRMC,125243.000,A,5255.1858,N,00129.3135,W,0.01,127.64,191214,,,A*7B",
poll=35, noreply=0, badformat=0, baddata=0, fudgetime2=400.000,
stratum=0, refid=NMEA, flags=5

Relevant bit of ntp.conf:

server 127.127.20.0 mode 17 prefer
fudge 127.127.20.0 time2 0.400 flag1 1 flag2 0 flag3 1 flag4 0 refid NMEA

Thanks in advance,
Neil. 		 	   		  


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