Date: Sat, 17 May 2008 08:43:03 -0500 From: David W. Hess <dwhess@banishedsouls.org> To: freebsd-hardware@freebsd.org Subject: Re: software null modems Message-ID: <fint24d6kjjn6u3u6007vplqja7esm5cts@4ax.com> In-Reply-To: <482C3875.1050509@gmail.com> References: <482C3875.1050509@gmail.com>
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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.
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