refclock 28 gone wacky on me

Gary E. Miller gem at
Thu Jun 9 23:08:10 UTC 2016

Yo Mike!

On Thu, 9 Jun 2016 18:21:32 -0400
Mike <bellyacres at> wrote:

> Forgot this in the original post...
> ntpshmmon version 1
> #      Name   Seen@                Clock Real               L Prec
> sample NTP0 1465510765.147894340 1465510765.120560175  1465510764.938999891 0  -1
> sample NTP0 1465510765.648664035 1465510765.468806532  1465510764.938999891 0  -1

> Is seeing NTP0 twice like this typical?

Nope, should be impossible.  Looks to be exactly 500 milliSec apart.
Do you have a square wave output?  Or a 2Hz output?

How about you put ppstest on it to see.  Except on the Pi you only
see one edge, so can not tell square wave from 2 Hz.  Got a scope?
What is the GPS again?

> I can't ever recall seeing it that way.

square wave is uncommon, but I have seen it.

What I have not seen is the gpsd edge detection circuitry output
2x in the same second.  There is supposed to be logic to prevent it, and
it used to work.

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