Unless you're using RS485.
> 10 Megabit ethernet cards are dirt cheap, and Cat 5 UTP cables are much,
> much cheaper than high-quality serial cables, and you can run them for a
> much greater distance without worrying about noise or signal degredation
> problems.
Unless you're using RS485, which gives you interesting, and extremely
important, properties like real-time performance guarantees, higher
reliability,....
Of course, perhaps if you used ARCnet instead of Ethernet, it'd be a different
story, but there's definitely a case for using RS485 for high-speed, real time
communications links.
tytso@MIT.EDU said:
> The only reason why high-speed serial might be interesting is for
> those IR ports that look like serial ports, and there aren't that many
> interesting applications requiring that yet. I do intend to fix this;
> I just haven't seen a huge urgency to it.
> If someone has an actual, real-life application, let me know....
Many fieldbus protocols are based on RS485, and I'm seeing a lot of interest
in running fieldbus protocols on Linux. These run speeds of up to 12Mb/s
I'd like to support the lowest level of various protocols, such a Profibus,
CAN, etc., as line disciplines, with the higher layers of the protocols in a
user-space library.
In order to do this we need support for high speed interfaces, and also for
synchronous operation.
The Infra-Red people have worked round this by providing dedicated drivers for
driving a 16550 synchronously. I don't really think that's a good idea,
and I was quite glad to see the N_HDLC synchronous-tty support which arrived
circa 2.2.5.
If we make the normal serial driver support this synchronous-tty mode, then it
can be used for IR support, and also fieldbus support, and the duplicate
drivers can be dropped.
---- ---- ----
David Woodhouse David.Woodhouse@mvhi.com Office: (+44) 1223 810302
Project Leader, Process Information Systems Mobile: (+44) 976 658355
Axiom (Cambridge) Ltd., Swaffham Bulbeck, Cambridge, CB5 0NA, UK.
finger dwmw2@ferret.lmh.ox.ac.uk for PGP key.
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