[time-nuts] Serial port server .. any interest in a write up on using ?

Attila Kinali attila at kinali.ch
Wed May 23 15:09:32 UTC 2012


On Wed, 23 May 2012 01:54:20 -0700
Hal Murray <hmurray at megapathdsl.net> wrote:

> > There aren't noticable more jitter for moderate (1-2 MByte/s) traffic.
> > (Probably visible if i would do a statistical analysis...but..) 
> 
> 1-2 megabytes/sec is 8-16 megabits/sec.  You won't get into serious troubles 
> until you saturate a link.  With modern CPUs, it's trivial to saturate 100 
> megabit links and not very hard to saturate 1 gigabit links.

Yes, i know. I deliberately did not saturate the link. I know that it looks quite differently if i do and that jitter will rise into the ms range even
on a local LAN. But anyone who does work with precision timing in such
an enviroment is lost anyways. If you do timing over ethernet, you are well
advised to use a seperate network that does not carry any other traffic,
use fast, low latency, high bandwidth switches, etc pp...

Ofcourse unless you go the way of IEEE1588, but then you're playing in
a different league and probably have the money to buy a Cs clock or two :-)

As for the problem of serial ports (to come back to the original topic),
i'd probably use just a bunch of USB serial cables (the ones from Exsys
work quite good) if i don't need any timing information. They are cheap,
readily available, and if they have FTDI chip, they also work fine.

For timing.. I don't know. But i guess a small PC with some RS232 cards
in (there are even 4port cards for PCI-E available, and they are not
expensive) would be more than enough for the needs i have.

Anything else seems to me like either overkill, or not fitting to the
problem description.


			Attila Kinali
-- 
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
		-- Tirin, The Dispossessed, U. Le Guin



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