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Subject: Re: software null modems
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On Thu, 15 May 2008 09:19:49 -0400, "Aryeh M. Friedman" =
<aryeh.friedman@gmail.com> wrote:

>I need a null modem and all I can find is straight through db25 cables=20
>and I want to avoid the paper clip trick if I can. So is there any way=20
>to create a null modem in software only?

Unless you have some really unusual hardware on at least one side, this =
will not be
possible.  With rare exceptions that occasionally show up in embedded =
systems, hardware
UARTs all have fixed function I/O pins.  This is even more the case with =
RS-232 (or
RS-422) because signal level translation from and to logic levels is =
needed.

It is not difficult to modify an existing cable as long as you do not =
need hardware flow
control.  Just swap pins 2 and 3.