8-bitters and multi-whatever
M H Stein
dm561 at torfree.net
Thu Sep 13 10:02:04 CDT 2007
Date: Wed, 12 Sep 2007 19:56:02 -0400
From: "Roy J. Tellason" <rtellason at verizon.net>
Subject: Re: 8-bitters and multi-whatever
On Wednesday 12 September 2007 19:45, Ensor wrote:
> > You don't even need "rs232 levels".
> MIDI is a "current loop" interface isn't it?
But my point is that in prototyping some small SBC the rs232 stuff is about
the only thing on there typically that needs other than logic power (+5V)
unless there's some analog stuff there on the board that needs it.
MIDI, in every implementation I've ever seen, uses only a 5V supply.
I never did understand why current loops weren't used more...
On short runs you can usually get away with TTL levels on RS-232 as long
as you limit the input voltage swing with a resistor and a couple of diodes
or use an optocoupler.
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