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Posted by ???????? (from: 194.250.97.214) on January 30, 2001 at 11:23:28:
In Reply to: MAKING A MIDI CABLE posted by Chezan mihai ciprian on March 31, 2000 at 07:23:54:
: Please send me some information about MAKING A MIDI
: CABLE
How to build a MIDI interface for a Sound Blaster/Sound Blaster Pro:
Probably works with almost any soundcard
The Sound Blaster MIDI port uses two pins from the 15 pin
joystick port. These normally would be redundant +5 volt and
ground lines. In the Sound Blaster, there are called MIDI TXD
(Transmit eXternal Data) and MIDI RXD (Receive eXternal Data).
The signals to and from the Sound Blaster 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 Sound Blaster
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 separately, but they share the +5 volt and ground lines.
(Pins 8 and 5 on the Sound Blaster). The interface uses 4 wire
shielded cable to connect the computer to the interface box and
two 2 wire shielded 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
220 resistor (from the +5 volt pin to pin 4 on the MIDI cable)
and a 220 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 below. Cut each trace on
both ends first, then remove the copper between the cuts.
RED = Remove BLUE = Marked as remove, but doesn't seem to be needed
Now Turn over, left to right...
BLUE = Link wires GREEN = Small components
Looking at the diagram, I now believe the links from IC2 pin 2 to IC1 pin 3, and IC2 pin 2 to pin 4, to be incorrect. The links IC2 pin 5 to pin 9 and IC2 pin 9 to pin 11 are only required if you intend to use the corresponding outputs - pins 6 and 8. This also explains the additional track cutting
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 above 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 shielded 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 above
schematic. Tie the cable shield 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. Connect 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 Sound Blaster 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 Sound Blaster. With "MIDI Mode" selected,
MIDI Note-On messages will play sounds from the Sound Blaster
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
Sound Blaster. All of Voyetra's sequencers, Cakewalk, and
Trax are examples of some that are available. When you go
shopping for a sequencer, make sure you specify that you have
a Sound Blaster. The Sound Blaster MIDI interface is NOT
Roland MPU-401 compatible! But that's not a major drawback
anymore - Most companies are now supporting the Sound Blaster,
but some have separate versions - One for SB, one for Roland.
There are some ShareWare/DemoWare sequencers available 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) - not that critical, really
R4,R5 220
R1 270
R2 1K
R3 4.7K
Capacitors:
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, 180ø
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 : (408)428-6660 1200/2400
Node 3 : (408)428-6662 9600/14400 v32/v32bis/CSP
Node 4 : (408)428-6664 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 (408)428-6600. Good luck!
Information presented from files obtained via the UK Creative BBS (now defunct), with suitable reformatting into HTML. All information presented is understood to be in the public domain and intended for distribution.
No responsibility accepted for damage or injury resulting from the use of this information - if in doubt, buy it, don't build it! All trademarks acknowledged, particularly CREATIVE, SOUND BLASTER etc. For Creative's web site, go to www.soundblaster.com ... www.creative.com is incorrect, but will offer a courtesy redirection.
A junkroom internet production, built entirely with freeware, cover CD and other legitimate but unpurchased software under Windows 3.1.
Webford 2.01 was used for some parts of the production, and to clean up the conversion of spaces to by Netscape Composter... I mean Composer... no I don't! This site could look a lot cleaner if I used more advanced code and the background is more of a liability than it's worth.
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