[time-nuts] Designing an embedded precision GPS time server

Gary E. Miller gem at rellim.com
Wed Oct 25 21:34:57 EDT 2017

Yo Nick!

On Wed, 25 Oct 2017 17:53:46 -0700
Nick Sayer via time-nuts <time-nuts at febo.com> wrote:

> This may be a fool’s errand, certainly, but looking at it from here,
> I would think that such a design might offer accuracy in the
> microsecond range,

I'm looking at 6 Raspberry Pi's right now, each with a different GPS
model.  Running NTPec and kernel PPS.  Adjacent jitter is from 10 to 35
micro seconds over 100 Base-T.

Local PPS jitter, is from 250 ns to up to 3,000 ns.

The biggest issue is the 186 ns granularity in the kernel system
clock.  Then interrupt latency and the usual Linux stuff.

> Anybody have any ideas or suggestions along these lines?

This may be not time-nutty enough for here.  Feel free to contact
me off list.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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