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

Scott Stobbe scott.j.stobbe at gmail.com
Tue Feb 14 17:26:16 EST 2017


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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