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Subject: Re: multiple devices on an RS232 connection

Date: 02/04/00 at 11:49 PM
Posted by: russ
E-mail: servocontrol@altavista.com
Message Posted:

In Reply to: multiple devices on an RS232 connection posted by jim witler on 02/03/00 at 8:12 AM:


I had to help this gal out (not hardware-type) who tried to do a similar thing: poll about a dozen
devices via 232, but the loading caused problems with proper threshold levels to be satisfied.

It was only a one-time R&D project, so i dug into the driver's abilities, and beefed up the
(er skewed) things to allow it to work with simply using a resistor (pull-up/down, i don't remember
at this point) and got it to work on the whole thing...good enuff for our task, but would not
recommend it for large-scale production.


: Hi,

: I am looking for a way to connect up to 10 RS232 devices to a single RS 232 port on a PC at one time and be able to gather data from each device
: sequentially.

: My thinking is to clock a 4017 (one of ten decoder) or similar chip with the DTR line and have it enable the first device, clock it again to enable the second device, etc.

: This solution will likely require converting from rs232 to ttl (or similar) to RS422 and back to RS232. Pretty messy!!

: Any other ideas?

: If you need further details contact me.

: Thanks
: Jim

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