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From: Peter Bennett
Subject: Re: RS232 - daisy chain - switch
Date: Sun, 24 Nov 2002 13:47:13 -0800
Organization: Home for the Hopelessly Helpful
X-Newsreader: Forte Agent 1.8/32.548
On Sat, 23 Nov 2002 16:30:17 +0100, "Nikolaj Christoffersen \(remove
>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.
Sounds like you have each unit repeating the messages for the
I recently did a system with a dozen daisy-chained devices on RS-232 -
Each device had a switch (which it controlled when it wanted to talk)
that connected the input of its "to PC" MAX232 converter to either its
own output, or to the input from the downstream units. Each unit
simply tapped off PC->device path, on the TTL side of the MAX232s.
This way, there was only a few microseconds of difference in timing
between the first and last device - just gate and wiring delays - as
the signals were not repeated by each device. This system requires
that the devices only talk in response to a message from the PC.
Peter Bennett, VE7CEI
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