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SubjectRe: serial.c (half duplex support)
DateMon, 01 Nov 1999 15:27:02 +0000
FromDavid Woodhouse <>

hps@tanstaafl.de said:
> Wouldn't it be easier to put a small microcontroller (say an 8051) on
> a board with a reasonable intelligent PCI bridge and implement the
> packet transfer in this controller? Then you would just put your
> telegram onto the chip, say "hey, send it out" and have no longer
> worry about specs?

Also being investigated. Actually, I prefer the idea of switching our fieldbus
to ARCnet - which can handle IP traffic as well as the low-level stuff. You can
get a chip with an 8051 core and an ARCnet core next to each other, which is
quite nice.

> Ok, you can't use your $10 standard PCI serial hardware, but at least
> any user could be assured that the right lamp / engine / magnet is
> turned on or off.

I fully intend to support 'decent' fast serial ports, running RS485 up to
1.5Mbaud, but I may have to build such boards myself - and if I want
widespread testing of my Profibus code, there's no substitute for commodity
hardware.

> If this protocol is only really reliable in hardware, why not
> implement it in hardware.

It's not that it's not reliable in software - it's just that we might not be
able to pass the certification in software - that's a different thing.

With a little care (and hdparm -u) we can get it to be _reliable_ without too
much trouble - this is Linux, after all.


---- ---- ----
David Woodhouse David.Woodhouse@mvhi.com Office: (+44) 1223 810302
Project Leader, Process Information Systems Mobile: (+44) 7976 658355
Axiom (Cambridge) Ltd., Swaffham Bulbeck, Cambridge, CB5 0NA, UK.
finger dwmw2@ferret.lmh.ox.ac.uk for PGP key.


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