Re: [gpsd-users] [gpsd-dev] SemPiTernal - Bounding PPS uncertainty

[Eric S. Raymond]

Hal Murray <address@hidden>:
> 
> >> Both are triggering on the rising edge.
> 
> > I want to be very sure I know what you're asserting here.  Are you saying
> > that you *know* the pps-gpio driver reports the leading edge in both cases?
> > While this is certainly plausible I'd like to know your authority for it.
> > It's a crucial, delicate point on which I would hate for us to inadvertently
> > spread misinformation. 
> 
> I was claiming that both devices are doing the right thing with the current 
> broken kernel that doesn't support the falling/clear edge.
> 
> I just verified with a scope that the PPS pulse from an Adafruit HAT is 100 
> ms wide and starts with a rising edge.

Excellent.  That's going to simplify the HOWTO a lot.  Thanks for clearing
up that point.

> I have an old Uputronics, but it's tie wrapped up on a shelf where I can't 
> easily get a scope probe on it.  They use uBlox.  I'm not sure which one.  It 
> is unlikely to make any difference.

Agreed.  The Ublox receivers are so obviously a class act (looking
from the software end that I understand) to make me very surprised if
they got this sort of lower-level detail wrong.

> > The default pulse width should be in the data sheets.
> 
> I couldn't find it.  Grumph.  So change that to "will be in good data sheets."

I concur with your grumph. :-)
-- 
                <a href="http://www.catb.org/~esr/";>Eric S. Raymond</a>