go3@prism.gatech.EDU (OLIVE JR,GEORGE A) (06/29/91)
I am trying to hook up an Opcode Studio Plus Two midi box to an '040 next. It
worked fine on the '030 but the RS423 ports on the '040 are incompatible
with the midi box. I called Opcode, and they gave me the following cable
diagram which they said people at NeXT gave them.
'040 Studio Plus Two
(RS423) (RS422)
(Signal GND) 4 ----- 6,8 (RXD+, TXD+)
(TXD) 3 ----- 4 (Signal GND)
(RXD) 5 ----- 3 (TXD-)
Unfortunately, this does not work, although it comes close. The NeXT can
read the midi keyboard, but when it attempts to talk to the synthesizer
it seems to feedback on the serial port causing the most bizarre echo effect.
The echo repeats forever the note that the NeXT was sending. Interestingly
it also injects new notes! How can that be?
Another problem is, when RXD+ and TXD+ are hooked together, the midi box
starts to "leak". The keyboard events are passed to the synthesizer
directly in addition to being routed through the NeXT. Sort of like a
midi thru connection. This is probably related to the echo effect.
I have also tried various combinations of the above interface. I tried
hooking (423 TXD) to (422 RXD-) instead of GND. I have tried hooking only
one of TXD+ or RXD+ to the (423 GND). Nothing fixes the problems.
Does anybody have a clue how this cable works? Has anybody hooked any
midi box to a NeXT.
This is a question I see asked a lot, so if people will send me the names
of midi boxes they have had success hooking to the '040, and cable
diagrams (vendors, part number, etc) if known, I will summarize this
information to the net.
--
OLIVE JR,GEORGE A
Georgia Institute of Technology, Atlanta Georgia, 30332
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