==============================
A cheap MIDI connector box
for the Sound Blaster card
v1.2 March 22nd, 1991
by
Adam Mirowski
mir@chorus.fr
==============================
Sound Blaster has a "built-in MIDI interface", but "all you need
is a MIDI Connector Box (optionally available) in order to connect
your SB to MIDI instruments or keyboards", says the add on the
box. The list price for that gadget is as high as $79.95 and
anyway it is not available here in France. Also, the MIDI
interface is not compatible with the MPU-401 standard (and de
facto norm) and is only one-way-at-a-time. So the box is not worth
the money, except if you try to set up it by yourself. For $5 you
can get the basic functionalities and for $10 everything which
comes with the original one.
I have heard on Usenet recently that Sound Blaster will soon come
out with a standard MIDI interface. Chances are that this circuit
will also work with that new version.
Corrections (AM): SB Pro doesn't seem to be MPU compatible;
it is already provided with a MIDI Adaptor
that you can also purchase separately for $25 (probably for
an old SB.) I suppose that the cabling of this MIDI adaptor
corresponds to paragraph II of the "SUPPLEMENT" (see below.)
I was also told that SB v2.0 has a bidirectional MIDI port.
This could be also the case for SB Pro.
Parts
=====
Qty Name Type Tandy ref
---------------------------------------------------
1 Optocoupler 4N25 276-9294
3 Resistors 220 ohm 271-015
1 Resistor 1 Kohm 271-023
1 AND gate 74LS08 276-9276
2 DIN plugs Female 5 pins 274-9110
1 Canon DB plug Male 15 pins Not sold
[1] Diode 1N914 or 1N4148 276-1122/276-9014
1 Veroboard (*) 5cm by 5cm
8 Wires Not shielded
1 Box to put all that stuff inside
[] - didn't use it myself.
(*) It is a piece of
epoxide with a raster of holes spaced at 2.54mm. On one side
there are preprinted copper tracks along each line of holes
(in one direction only). You cut off unused portions of the
tracks and join the other with straps, so as to get a
primitive form of a printed circuit board. You then insert the
electronic parts and solder them.
Sound Blaster MIDI/Game connector REAL cabling
==============================================
+------------------------------------------+
! Pin Signal !
!------------------------------------------!
! 1 +5V !
! 2 X button for joystick A !
! 3 X potentiometer for joystick A !
! 4 Ground !
! 5 Ground !
! 6 Y potentiometer for joystick A !
! 7 Y button for joystick A !
! 8 +5V !
! 9 +5V !
! 10 X button for joystick B !
! 11 X potentiometer for joystick B !
! 12 MIDI out !
! 13 Y potentiometer for joystick B !
! 14 Y button for joystick B !
! 15 MIDI in !
+------------------------------------------+
The interesting pins are 12, 15, 4 (or 5) and 9 (or 8 or 1).
BTW, if your joystick Y cable assumes that pin 12 is ground (as it
is on a normal game port), it will not work with the SB.
... 'Son,' he said, 'Grab your things I've come to take you home!'
--- PPoint 2.06
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* Origin: Seven Wells On-Line * Nashville, TN (1:116/30.3)
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