[ntp:questions] Standalone PPS

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Thu Jun 13 12:45:36 UTC 2013

patrick200075011 at gmail.com wrote:
> Hi
> The super stable means easily 1ppm which means about one second every
> 16 days. Get a look to www.matel-fordahl.fr or www.kvg-gmbh.de .
> However my PCB can be implemented with classics DIL14 pins 1 7 8 14
> footprints for people who has very bad computer clock or simply wants
> to put the clock outside the hot computer box or even outside the hot
> computer room.

What you really need is to interface your board with an external PPS 
source, i.e. a cheap (SURE/GARMIN) gps so that you can steer that 
internal osc to lock onto the absolute time signal.

This will give you the best of both worlds: Both accurate and stable!

> My goal is to keep internal machines on time to each other more than
> to keep an absolute clock. The internal ntp is enough for that as
> networks are 100M or 1 giga. The PPS is used only to MY stratum 0 (my
> PCB has 2 outputs as the max232 has 2 but I am using only one for the
> ntpd).
> The orphan mode is never used as long as a source is available. The
> 127.127..1.0 IS always available, it is this one that I need to get
> rid after the initialization.
> The problem is here: I need the local for initialization. But the
> local later on makes a conflict because it is a bad source.
> The time1 and time2 would have been the solution to adjust the phase
> on startup but I don't want to do that on each power up. I can do
> that if I would be able to use back quotes to call a script.
> Cheers

- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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