Hello Iain,

The MIDI outputs are not opto isolated, but the MIDI inputs are. From the
MIDI OUTPUT pin connect a 220 to 270 ohm resistor to pin 5 of the female DIN
output connector, and a 220 Ohm resistor from PIN 4 of the din output
connector to +5 Volts. This will interface to any standard MIDI cable and
MIDI instrument.

The PIC can drive the MIDI out just fine...connect PIN 2 of the DIN
connector to ground.

On my website see the MIDI encoder sections, some of the encoders also have
data sheets in .pdf format. Just click on technical information (Gree
highlight) to down load. The PEDMUX series, abe about as simple as you can
get with a MIDI encoder.

Vern
----- Original Message -----
From: iain duncan <iainduncan@TELUS.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, August 23, 2004 3:45 AM
Subject: Re: multiple 4x4 keypads to 16f877 or 18f452?


> Bob Ammerman wrote:
> > MIDI in and out work fine on a traditional UART. The baud rate is 31
250,
> > which works out perfectly when using an crystal that is an exact number
of
> > MHz (as opposed to some funny number).
> >
> > However, rather than using conventional RS232 levels, proper MIDI uses
an
> > opto-isolated connection.
>
> Bob, what's the deal with the opto-isolation? I've noticed some examples
> on line have it, some don't. Do I *need* to include opto-isolation to
> just get simple output, or is there some other way? And why is
> necessary, ie why can't I just bring down the voltage level on the pins
> to acceptable midi range using diodes or what not? ( Am very much a
> beginner with electornics. I am more scared of external chips than I am
> of bit banging serial i/o myself, ha ha. )
>
> Iain
>
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