Interface cabling
                             =================
     
     The cabling  is roughly the same as in the MIDI 1.0 Specification,
     except that I used a different optocoupler and "AND" gates instead
     of inverters (simply because Tandy sold the former with docs :-).
     
     Numbers between  parentheses are  pin numbers. ICs have a standard
     pin numbering  scheme. Other  parts have  pin numbers  written  on
     them. For  resistors, it's  simply to  make difference between the
     two ends.
     
                          6    5    4
                       +--!----!----!--+
         Usually       !               !         IC seen from the top
         a hole -->    >               !
                       !               !
                       +--!----!----!--+
                          1    2    3
     
     "MIDI-in", "MIDI-out"  design the  female MIDI  plugs. "Game/MIDI"
     designs the 15 pin female connector on the SB.
     
     
         FROM PIN                 TO PIN
     
     MIDI input part
     ---------------
     MIDI-in (4)             Resistor1 220ohm (1)
     Resistor1 220ohm (2)    Optocoupler (1)
     Optocoupler (2)         MIDI-in (5)
     [Optocoupler (1)        Diode -]
     [Optocoupler (2)        Diode +]
     
     Games/MIDI (9)          Resistor4 1Kohm (1)
     Resistor4 1Kohm (2)     Optocoupler (5)
     Games/MIDI (15)         Optocoupler (5)
     Optocoupler (4)         Game/MIDI (4)
     
     
     MIDI output part
     ----------------
     Games/MIDI (12)         AND gate (1)
     AND gate (1)            AND gate (2)
     AND gate (3)            Resistor2 220ohm (1)
     Resistor2 220ohm (2)    MIDI-out (5)
     MIDI-out (4)            Resistor3 220ohm (1)
     Resistor3 220ohm (2)    Game/MIDI (9)
     Games/MIDI (9)          AND gate (14)
     Games/MIDI (4)          AND gate (7)
     
     
                               Final remarks
                               =============
                                      
     When using  a "veroboard", don't forget to cut tracks under the IC
     and the optocoupler, or they will be short-circuited.
     
     You will probably also want to setup two MIDI cords, to attach the
     interface to  an instrument.  To stay under $5, you could use male
     plugs instead  of female  ones for  the interface  and  plug  them
     directly into the instrument.
     
     When preparing the cords, be careful about not swapping the wires.
     The pin 4 from one plug must be wired to pin 4 from the other end,
     and the  pin 5  must be  attached to pin 5. None of the other pins
     must be  wired, nor the overall cable shielded. There is no ground
     in MIDI cords.
     
     If you  want more  outputs, you  have to  slightly extend the MIDI
     output part.  I would rather have only one AND gate input attached
     to the  SB MIDI-out  pin and  only one  MIDI-out plug per AND gate
     output. If  Creative Labs  offer  5  MIDI  outs  in  the  original
     Connector Box,  it is  probably because  they use simple inverters
     (or buffers)  and there  are 6  per IC.  As I  previously said,  I
     bought AND  gates only  because they  had  data  sheets  attached,
     whereas inverters/buffers had not...
     
     Direct your remarks to mir@chorus.fr, or to
     
                M. Adam Mirowski
                Chorus systemes
                6, avenue Gustave Eiffel
                F-78182 Saint-Quentin-en-Yvelines CEDEX
                FRANCE
     
     My phone number is +33 (1) 30-64-82-00
     
     I obviously  won't take  any responsibility  for the  damages  you
     could do  to your  Sound Blaster  or to  your MIDI equipment while
     using this interface.
... Close to the Edge, down by the river.
--- PPoint 2.06
---------------