[time-nuts] Testing frequency using NTP

Poul-Henning Kamp phk at phk.freebsd.dk
Thu Oct 2 03:02:31 EDT 2008


In message <1231b6a80810012218t8f9b37y7395215c24229305 at mail.gmail.com>, "Steve 
Rooke" writes:
>2008/10/2 Bruce Griffiths <bruce.griffiths at xtra.co.nz>:
>
>> Save yourself a counter and just divide the frequency down to about 1Hz
>> and time stamp the 1Hz transitions with the Linux box.
>> As long as you know the division factor its easy enough to calculate the
>> frequency.
>
>I'd planned on a simple interface to the PC via using the parallel,
>suitably strapped, as a basic output port. Now, I could use it as an
>input but I'd probably have to poll the port which would be somewhat
>inefficient [...]

Linux should have the PPS-API from RFC2783 so that should be piece
of cake to do.

I know that it works in FreeBSD (guess who wrote it :-) where you can
just:
	cd /usr/sc/tools/test/ppsapi
	make
	./ppsapitest /dev/lpt0



-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.



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