The World of Computer Software/The World of Computer Software.iso/mididiag.zip/SBMIDI.TXT

Text File | 1992-03-25 | 7KB | 153 lines

      How to build a MIDI interface for a SoundBlaster/SoundBlaster Pro:

      The SoundBlastr MIDI port uses two pins from the 15-pin
      joystick port.  These normally would be redundant +5volt and
      ground lines.  In the SoundBlaster, there are called MIDI TXD
      (Transmit eXternal Data) and MIDI RXD (Receive eXternal Data).
      The signals to and from the SoundBlaster are TTL logic signals.
      MIDI uses a current loop interface, so the job of the interface
      box is to convert between TTL-level signals and the MIDI current
      loop.

      If you want to use the MIDI interface and the SoundBlaster
      joystick interface simultaneously, you can make a simple adapter
      by connecting one male and 2 female 15-pin connectors to a short
      length of ribbon cable.

      SBMIDI1.PCX is a PCX format graphic file of the schematic diagram
      of the MIDI connector circuitry.  You can use Windows Paintbrush
      to view and print the schematic.

      For simplicity, the schematics show the MIDI input and output
      circuits seperately, but they share the +5volt and ground lines.
      (Pins 8 and 5 on the SoundBlaster).  The interface uses 4-wire
      shielded cable to connect the computer to the interface box and
      two 2-wire sheilded cables to connect the interface box to the
      input and output ports on the MIDI instrument.

      The MIDI input port only can connect to one instrument, but the
      MIDI Out from the computer could go to up to 5 MIDI instruments.
      The schematic diagram only shows one complete MIDI output line.
      You can connect up to 4 additional MIDI outputs by adding a
      220Ω resistor (from the +5volt pin to pin 4 on the MIDI cable)
      and a 220Ω resistor (from the buffer output to pin 5 of the
      MIDI plug) for each output.  You should also add a 220pf
      capacitor between each additional MIDI line and ground.


      Construction:

      Start with using half of a dual 20-pin IC board, using the first
      six pins for the optocoupler and the last fourteen pins for the
      hex buffer.  Then remove portions of some of the copper lines
      on the circuit board with an X-Acto knife, as is shown in the
      schematic in the SBMIDI2.PCX graphic file.  Cut each trace on
      both ends first, then remove the copper between the cuts.
      Now on to component installation!  Be sure to use rosin-core
      solder and a low-wattage soldering iron.  Solder the 20-pin
      socket to the center of the board, being careful not to bridge
      solder between connections.  Then install the other components
      in the locations shown in the SBMIDI3.PCX schematic.  While
      looking at the SBMIDI3.PCX schematic, note that the ringed end
      of diode D1 needs to connect to pin1 of the optocoupler.
      Be sure to run hookup wires from the ground pin on the optocoupler
      (Pin 4) to the ground pin of the hex buffer (Pin 7) and between
      pins 11 and 12 on the hex buffer.  The remaining hookup wires
      are optional for additional MIDI outputs.  Notice that both a
      resistor and a capacitor must be connected in the same hole for
      each MIDI Out.  Then connect the 4-conductor sheilded cable to
      pins 5,8,12 and 15 of the 15-pin plug.  Connect the shield to
      the metal case of the plug.  Connect the other end of the 4-wire
      cable to the corresponding locations shown in the SBMIDI3.PCX
      schematic.  Tie the cable sheild to the large mounting hole in
      the circuit card and connect one end of each of the two connector
      shielded cables to pins 4 and 5 of the MIDI plugs.  Connnect the
      shield in the MIDI plugs to pin 2.  Mark one cable "MIDI IN" and
      the other cable "MIDI OUT".  Connect the other end of the cables
      tot he corresponding locations on the circuit card.  Tie the
      shields to mounting holes in the circuit card and connect all
      three shields together with a hookup wire.   Check the card and
      cables to ensure that all connections are correct, file small
      notches in the cover of the aluminum box for the cables, and
      wrap a piece of heavy paper around the circuit card to prevent
      shorting.  Your next step is to plug the 15-pin connector into
      the SoundBlaster and the MIDI In and Out to the MIDI jacks on
      your MIDI instrument.


      Testing:

      A MIDI port requires software to function.  You can test the
      input portion of the MIDI interface with the FM Organ program
      bundled with the SoundBlaster.  With "MIDI Mode" selected,
      MIDI Note-On messages will play sounds from the SoundBlaster
      card, but only those notes valid for the musical key you have
      selected.  For example, if you select the key of C, only the
      white keys will sound.  To test the MIDI Out portion of the
      interface, you can use any MIDI sequencer that supports
      SoundBlaster.  All of Voyetra's sequencers, Cakewalk, and
      Trax are examples of some that are avaliable.  When you go
      shopping for a sequencer, make sure you specify that you have
      a SoundBlaster.  The SoundBlaster MIDI interface is NOT
      Roland MPU-401 compatible!  But that's not a major drawback
      anymore - Most companies are now supporting the SoundBlaster,
      but some have seperate versions - One for SB, one for Roland.
      There are some ShareWare/DemoWare sequencers avaliable on
      the Creative Labs BBS.  You can reach them by modem at the
      number given at the end of this file.


      Parts List:

            Resistors:
            (¼-watt, 1%, metal film)
               R4,R5  220Ω
               R1     270Ω
               R2     1KΩ
               R3     4.7KΩ

            Capacitors:
            (25 working volts or greater)
               C1,C2  220pF ceramic

            Diodes:
               D1     1N914 or 1N4148

            Integrated Circuits:
               IC1    4N35 Optocoupler
               IC2    7407 Hex Buffer

            IC Sockets:
              (IC1)   8-pin
              (IC2)   14-pin

            Other Components:
               1 Dual IC board, Radio Shack part #276-159
               1 15-pin male DB-style connector, solder cup
               1 Hood for 15-pin DB connector
               2 5-pin DIN plugs, 180°
               1 Aluminum project box, approx. 3"x2"x2"
               2' of 4-conductor shielded cable
               8' of 2-conductor shielded cable


     Other info:

     Creative Labs, Inc. BBS:

              Node 1 & 2 :  [phone]  1200/2400
              Node 3  :     [phone]  9600/14400 v32/v32bis/CSP
              Node 4  :     [phone]  9600/14400 v32/v32bis/HST

     Available on the BBS is a library of MIDI files (.MID) as well
     as several ShareWare/DemoWare MIDI applications.

     Note:  Please do NOT call the Technical Support department of
     Creative Labs for help on this - With this file, you have
     just as much information as they do!  If you don't want to
     deal with it, just _buy_ the cable - It costs $24.95 + S&H
     direct from Creative Labs.  The sales number is [phone].

     Good luck!