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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