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Date:      Thu, 26 Jan 2017 22:28:23 -0800
From:      "Tony Hain" <tony@tndh.net>
To:        "'Ian Lepore'" <ian@freebsd.org>, <freebsd-arm@freebsd.org>
Subject:   RE: BBB uarts & pps dts definitions
Message-ID:  <041c01d27866$95a6ce60$c0f46b20$@tndh.net>
In-Reply-To: <1485484023.30533.102.camel@freebsd.org>
References:  <03a801d2776e$cae997e0$60bcc7a0$@tndh.net>			 <1485400906.30533.54.camel@freebsd.org>			 <03bb01d2779d$45d6edd0$d184c970$@tndh.net>			 <03c101d277ae$70f142c0$52d3c840$@tndh.net>		 <1485445768.30533.68.camel@freebsd.org>		 <040101d27816$3f7547b0$be5fd710$@tndh.net>	 <1485466405.30533.96.camel@freebsd.org>	 <041a01d2782d$bee11850$3ca348f0$@tndh.net> <1485484023.30533.102.camel@freebsd.org>

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Ian Lepore wrote:
=20
> On Thu, 2017-01-26 at 15:41 -0800, Tony Hain wrote:
> >
> > >
> > > -----Original Message-----
> > > From: Ian Lepore [mailto:ian@freebsd.org]
> > > Sent: Thursday, January 26, 2017 1:33 PM
> > > To: Tony Hain; freebsd-arm@freebsd.org
> > > Subject: Re: BBB uarts & pps dts definitions
> > >
> > > On Thu, 2017-01-26 at 12:53 -0800, Tony Hain wrote:
> > > >
> > > > Ian Lepore wrote:
> > > >
> > > > >
> > > > >
> > > > > >
> > > > > >
> > > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > snip
> > > > > >
> > > > > > [even more snip]
> > That makes some degree of sense based on what I am seeing, though =
that
> > is a very low input impedance on the BBB. I was expecting ~100k. My
> > source is a
> > 555 on an ancient ttl/RS232 board I built because the 20 us pulse =
from
> > the GPS was too fast (between the slew rate of the 3232 and the DCD
> > detection window on the com port) to go with a simple level
> > conversion. Sounds like it might be best to do an active 3.3v driver =
at
this
> point.
> >
> > Tony
>=20
> BTW, not related to the BB stuff... a while back I added "narrow pulse
> capture" support to uart(4) for CTS/DCD PPS capture, you can use it =
with
> pulses as narrow as 1uS, maybe even less on some hardware. =A0The =
tradeoff
is
> that you can only capture assert edges, not clear. =A0The support goes =
back
to
> 10.3 or so, details are in the uart(4) manpage.

I saw references to that and was going to go looking for them again if =
the
timer pin approach failed. I was not overly hopeful though because it =
was
not clear to me how that would mesh with using NTPsec which would be
expecting a DCD transition. Let's hope the fix in the other note =
resolves
this so I never have to worry about that.

Tony
=20




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