Newsgroups: rec.audio.tech
Subject: Re: MIDI-to-computer interfaces
References: <[email protected]>
"Christian E. Boehme"  writes:

> I recently acquired a MIDI synth that I would like to control
> from a serial I/O (RS-232/RS-422) equipped computer. Now, this
> particular synth does NOT come with a "To Host" interface which
> forces me into getting myself some serial-to-MIDI interface
> thingy to plug in-between. I checked around a little bit for
> what's available and came to wonder what kind of magic usually
> goes INTO those boxes. 

To my understanding they have two UART and some buffering
electronics in between.

> I mean, given a properly timed RS-232/422
> signal with respect to MIDI, what else is needed to make this a
> proper MIDI signal in terms of timing and voltage levels ? Can't
> be much in there ... Anyone out there who may have gone the
> "thru cable approach" ?

MIDI is a current loop interface, where RS-232/422 is voltage
level based interface. For transmitting part some diode+resitors
would be enoug to convert voltage to current. For receving
an optosolator with some components surrounding it is needed.

And the pther thign is that normal RS-233/422 ports available
for PCs do not support the data rate MIDI uses (31250 bps if I
remebr right). If you know electronics and want to experiment,
you should be able to change the clock crystal in the I/O card
to make it possile to operate at the MIDI rate.

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/