Hello,

this a circuit diagram of an interface I built to connect midi equipment to my 68040 based NeXT computer. It is connected to one of the serial ports and simply does some voltage level conversion and opto isolation.
The  interface needs a supply voltage of 5V which can be supplied with batteries or NC accumulators (p.e. 4*1.2V) or you can use the 12V from DSP port and convert them to 5V using a 7805 voltage level converter (sorry this part is not shown in the circuit diagram).

As indicated by the arrows on the left side of the diagram, the label "MIDI in" specifies the input of the interface and must be connected to the "MIDI out" port of your MIDI equipment.
Unnecessary to mention that the  the label "MIDI out" specifies the output of the interface and must be connected to the "MIDI in" port of your MIDI equipment.

The pinout of your NeXT serial port is shown in your "NeXT Users Reference" p.292 (or "NeXT-Benutzerhandbuch" Seite 363)  you should have got with your station. 
 
¬

Though this interface works fine with my equipment for more than half a year now, I cannot take any responsibility . Use it at your own risk!
Especially I drew this circuit diagram after I built my interface, so the diagram may still contain errors! It would be nice if anyone who has successfully built the interface from this diagram drops me a line that it is correct or mails me any errors he found.

Some MIDI software is coming from me soon.

Have fun,

Dirk Schwarzhans
(dirk@kalium.physik.TU-Berlin.DE)
V1.0: April, 21 1995