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From: Grahame Kelly
Subject: Re: RS232 - daisy chain - switch
Date: Sat, 23 Nov 2002 18:51:50 GMT
NNTP-Posting-Date: Sun, 24 Nov 2002 05:51:50 EST
Nikolaj Christoffersen (remove XPKZ) wrote:
> I have a PC (windows) communicating with 36 hardware units through RS232.
> The 36 units are daisy chained. The control program running at the PC
> gives every unit a number.
> Does anybody know if it is possible to get some sort of RS232 switch where
> I can connect my 36 units in 4 groups of 8 and still have my control
> program and see all 36 units at one time. My problem is that communication
> to unit 35 is to slow.
I would guess that your windows s/w is handling the unit ID with some
special communications protocol. The only way your possibly going to speed
up the communications with all these serial units is to spread them over
several serial lines (i.e. Put 9 each on say 4 serial lines - You may have
to purchase a multi-serial-io PCI card with 8 or 16 additional serial lines
to do this if your system doesn't have enough lines). Of course if you
can't get the s/w to concurrently communicate over more than one serial
line then you "up the creek without a paddle" anyhow, and I wouldn't waste
your time trying.
Any type of RS232 switch will probably not work (because how/when will it
know to switch the line to a particular serial ID device) unless you know
the communications protocol, mod the s/w driver and get it to talk to an
intelligent RS232 switch. If you know the protocol - then you could build a
uP (microprocessor) circuit to do the serial switching on demand for you.
All it would take is a uP and 4+1 UART lines and some buffer memory.
My 2c anyhow.
Grahame (at) Wildpossum (dot) com
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