console multiplexor

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Wed Oct 4 11:53:59 2000

At 01:52 AM 10/4/00 -0800, Mike Ford wrote:
> >> Now all I need is a console multiplexor.
> >
> >Any idea's? This is something I *REALLY* need.
>
>Want to explain a bit more what it really is, what might be printed on its
>box etc.?

Well in this case I was talking about a multiplexor for DEC RS-423
consoles. I suppose this would have some number of MMJ ports (no doubt an
odd number :-) and one would go to one's "console" and the others to the
other machines you are controlling.

Clearly the simplest solution is a 6PnT rotary switch, some cables wired up
with MMJ plugs crimped on their ends. I'm planning to build one of these as
I have all the parts and that will get the console going on the micro-cluster.

Somewhat more clever is to use a CMOS switch and some push buttons with
LEDs and get the whole thing to be 'lectronic. You could have an LED
indicate which console was selected and another to show traffic on that
console. If I get ambitious this is the first one I'll actually build
(skipping #1 above).

However, if you're willing to be really clever then you can do much better
than this. I've got a nice color terminal (the Link MC70 although its color
is a bit unstable these days :-() or I could use a DEC VT340 (probably the
actual version for display) and you could, with a bit of smarts and some
buffering take output from the RS-423 lines, and prior to forwarding them
on to the terminal you could inject ANSI color codes on/off. This would
make the output from each console a different color. (keeping them straight
is of course the challenge) If you are really clever you don't allow one
console to interrupt another mid-line either. I've got an old single board
Z80 system that could probably do this, or I could wimp out and use a CPLD
feeding a Scenix chip.

Anyway, all that aside. If you come across a box that has a selector switch
on the front and a row of MMJ's on the back, that is probably what I'm
looking for :-)

--Chuck
Received on Wed Oct 04 2000 - 11:53:59 BST