Re: [gpsd-dev] RFC 2783

[Hal Murray]

address@hidden said:
> Is there always, and necessarily, only *one* pps device?

No.

If nothing else, I want to be able to connect two so I can compare them.


The kernel time stamping also counts events.  That's a convenient hack for 
measuring things.  So gpsd and ntpd have to be sure not to gobble up a PPS 
device that isn't theirs.

Here is a graph made by feeding the 60 Hz power line via a transformer into a 
PPS input and counting cycles:
  http://www.megapathdsl.net/~hmurray/time-nuts/line/Dec-2013.png

I think the Linux kernel supports PPS via the printer port.  I haven't tried 
it, but the printer port is an old standby for hardware hacking.


-- 
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