refclock 28 gone wacky on me

Mike bellyacres at
Fri Jun 10 00:52:47 UTC 2016

On 06/09/2016 08:37 PM, Gary E. Miller wrote:
> Yo Mike!
> On Thu, 9 Jun 2016 20:26:01 -0400
> Mike <bellyacres at> wrote:
> Skytraq ships varying firmware, so that is not definitive.
> Worse that says this:
>      "The 1PPS pin is multiplexed with some debug mode function whose
>      mode is to be determined at end of power on reset cycle. To avoid
>      incorrect function do not pull-up or pull- down this signal."
> What could possibly go wrong there?
Okay, that looks really suspect to me.  I'll try and get this thing 
connected to a Windows box and see if their utility will show me any 
useful info.
> And the serial is connected directly to a RasPi?
Yes, it's directly connected to the Pi.
>> If I hook it up to a PC, or with a serial to USB adapter will I be
>> able to see more about the edge being seen?
> Depends how good you are.  I leave that to you.
Okay, a learning challenge!
> No double pulse there.  Looks good.
> Hmm, it just occured to me, it is your SHM0 that is sending 2 updates
> a second?  Was it the SHM0?  If so, that is not a problem, as long
> as the time stamps look right, it just means the NMEA is reporting 2x
> a second.  The only thing we care about is the SHM1.
Yes, it was SHM0
> I still need the debug output.  Send me the result of this:
> 	# gpsd -nND 9 /dev/ttyXX |# fgrep PPS > gpsd.log


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