Stratum 1 HowTo

Hal Murray hmurray at
Fri Oct 13 02:54:39 UTC 2017

(Argh, I forgot to cc users@ on my first try.)

dropkick23 at said:
> From the howto: "The important thing to check is whether
> the pps-gpio driver triggers on assert or falling edge."

> How do you check? 

The easy way is to look in the table just above that line.  If that fails, 
maybe the documentation for your unit has the info.

The real way is to get out an oscilloscope.  1/2 :)

Another possibility is to sanity check things by running NTP.  If your PPS is 
off by 100 ms or 500 ms, you are probably triggering on the wrong edge.  That 
approach won't help if your pulse is only 10 microseconds wide.

Some GPS units allow you to adjust the width of the PPS.  If changing it by 
100 ms doesn't change what NTP sees, you are probably triggering on the 
correct edge.

These are my opinions.  I hate spam.

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