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

[Bob Camp]

Hi

If you want a 1588 PHY and are on a budget:

https://www.digikey.com/products/en/development-boards-kits-programmers/evaluation-boards-embedded-mcu-dsp/786?k=freescale+freedom&k=&pkeyword=freescale+freedom&pv47=24619&FV=ffe00312%2C7e80098&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

Drop NTP into it and let it rip.

Bob


> On Feb 14, 2017, at 5:26 PM, Scott Stobbe <scott.j.stobbe at gmail.com> 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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