[time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards

[J. Grizzard]

I really recommend the PC Engines apu2c hardware. Just a touch over $100,
schematics available, hardware serial port, GPIO, 1588-capable PHY, CPU
crystal accessible if you want to try a clockblock-type hack, great
support, and just decent all around.

There's also test pads for the PHY that could be used to do PPS directly
to that for PTP purposes, but I haven't quite yet figured out exactly
how to set that up. But the pads are there!

(hint: Order direct from manufacturer, not via a US distributor. You'll
save money and the shipping is still really quite fast.)

-j

On Tue, Feb 14, 2017 at 05:26:16PM -0500, Scott Stobbe wrote:
> Something like this would make a great NTP server.
> https://www.digikey.com/products/en?keywords=P0286-ND
> 
> Too bad they didn't include a PTP 1588 capable PHY...
> 
> On Tue, Feb 14, 2017 at 12:33 PM, Chris Albertson <albertson.chris at gmail.com
> > wrote:
> 
> > Here is a something that could work.  It has a real serial port and you
> > could add more ethernet controllers, uses very little power and cost only
> > $60.
> > www.newegg.com/....
> > <https://www.newegg.com/Product/Product.aspx?Item=
> > N82E16813157497&cm_re=j1900-_-13-157-497-_-Product>
> >
> > There are other boards like this that use the same J1900 CPU.   I'm
> > thinking about using this as th machine tool (milling machine) controller.
> >
> > On Tue, Feb 14, 2017 at 4:26 AM, Bob Camp <kb8tq at n1k.org> wrote:
> >
> > > Hi
> > >
> > > A direct port might be a +/- 100 ns sort of thing most of the time and a
> > > +/-10 us
> > > thing every so often under some OS???s. Most desktop operating systems are
> > > not
> > > designed to prioritize random pin interrupts. A dirt cheap MCU coded with
> > > a few
> > > (hundred) lines of assembly code may be a better option than a typical
> > > desktop.
> > > Complicating this further is the degree to which some OS???s can be
> > directly
> > > or
> > > indirectly optimized. Install *this* package and it all goes nuts.
> > Install
> > > that package
> > >  and not much happens ???.
> > >
> > > Bob
> > >
> > > > On Feb 13, 2017, at 11:07 AM, Ruslan Nabioullin <rnabioullin at gmail.com
> > >
> > > wrote:
> > > >
> > > > Hi, generally speaking, what are the performance differences between
> > the
> > > following: 1. direct RS-232 (i.e., what I believe is a standard PCI card
> > > offering RS-232---essentially UARTs interfaced more-or-less directly to
> > the
> > > PCI bus); 2. RS-232 via USB; 3. PPS decoding PCI cards (which might also
> > > have an IRIG input or even an onboard GNSS receiver).
> > > >
> > > > Thanks in advance,
> > > > Ruslan
> > > > _______________________________________________
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> >
> >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
> > _______________________________________________
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