Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cornell!uw-beaver!ubc-cs!alberta!edson!scott
From: scott@edson.ee.UAlberta.ca (Scott Stephens)
Newsgroups: comp.sys.amiga
Subject: Re: MIDI interface schematic
Message-ID: <1989Sep1.174603.14938@edson.ee.UAlberta.ca>
Date: 1 Sep 89 17:46:03 GMT
References: <22969@louie.udel.EDU>
Reply-To: scott@edson.UUCP (Scott Stephens)
Organization: U. of Alberta, Edmonton, AB
Lines: 32

In article <22969@louie.udel.EDU> wilts@cavax.ab.ca (Ed Wilts) writes:
>
>>>I need a MIDI interface and found an old schematic for one that
>>>someone designed -- 1 IN, 2 OUTS, 1 THRU.  It consisted only of a few
>>>hex-inverters, an opto-isolator and some resistors.  I realize that
>>>because of the Amiga's UART not a whole lot more is required, but can
>>>this possibly be all that needed?
>
>You can also find the schematic in a very old Amazing Computing, a back
>
>from the Amiga.  It'll be a little easier if you ever upgrade to a 500/2000.
>Base it on the 74LS04 instead of a LM339 and you only need a +5 signal (and
>no -5) and you can easily generate this from a cheapo wall transformer from
>Radio Shack pumped through a 7805 voltage regulator.
>
>Enjoy!
>
>        .../Ed          (Wilts%CaVax.AB.CA@UncaNet.Bitnet)
>Ed Wilts
>Sr. Systems Analyst, Canadian Occidental Petroleum Ltd.
>Calgary, Alberta, Canada                 (403) 234-1007

The Amazing Compute article was in Vol. 2 # 2, I built it and it works just
fine. I'd use a 74LS14, rather than a 7404, because of the Schmitt triggers,
but since these parts will not go to negative voltages, are you SURE it will
drive the Amiga input and the inputs to the Synths???? Also the only schematic
I've got for an LM339 shows an inverting output on output 3 (this from a 
Motorola data book), and this should be used to drive the RS232 line to the
Amiga (I can't remember whether I actually checked this or not, but the worst
that would happen would be driving the Amiga with inverted data).

R. Scott Stephens