[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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