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r2 - 2007-10-04 - 01:41:13 - RandallPrenticeYou are here: NTP >  Support Web > ConfiguringNTP > ConfiguringRefclocks > ConfiguringSHMRefclocks
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REFACTOR See ConfiguringSHMRefclocksDev for discussion of this topic.

Under LINUX there is the gpsd service which provides SHM services.

In ntp.conf include lines:-

# ... and use gpsd daemon for time sync

server 127.127.28.0 minpoll 4 maxpoll 4

fudge 127.127.28.0 time1 -0.245 refid GPS stratum 15

server 127.127.28.1 minpoll 4 maxpoll 4 prefer

fudge 127.127.28.1 refid GPS1

gpsd then provides the following (from ntpq):-

remote refid st t when poll reach delay offset jitter

= =       =   =     =   =   === ==

LOCAL(0) .LOCL. 13 l 21 64 377 0 0 0.002

=-SHM(0) .GPS. 15 l 9 16 377 0 36.775 12.287

*SHM(1) .GPS1. 0 l 6 16 377 0 0.032 0.003

Note:

SHM(0) is the time from NEMA string (to establish second) this can deviate a lot, recommend you add another server (Not shown).

SHM(1) is the PPS from GPS

Related Topics: SHMRefclockUsers

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