8-bitters and multi-whatever

[Roy J. Tellason]

On Thursday 13 September 2007 11:02, M H Stein wrote:
> ------------Original Message:
> 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:
> > Hi,
> >
> >   > You don't even need "rs232 levels".
> >
> > MIDI is a "current loop" interface isn't it?
>
> Yup!
>
> 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...
>
> ========================
> -----------Reply:
>
> 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.

Hmm.  TTL levels and an opto?  Sounds like MIDI to me...   :-)

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