››››  Article 4783 of comp.sys.atari.8bit:›  From: terpin@acsu.buffalo.edu (christophe d terpin)›  Newsgroups: comp.sys.atari.8bit›  Subject: Homemade MIDI Interface -- Part 1 of 2›  Summary: How to build midi interface for Atari 8bit›  Keywords: MIDI, interface›  Date: 28 Mar 91 02:51:18 GMT›  Sender: news@acsu.Buffalo.EDU›  Organization: SUNY Buffalo›  ›  ›  Homemade MIDI interface for the Atari 8-Bit›  -------------------------------------------›  Parts List:›  1   7404 TTL Hex Inverter OR 7400 NAND gate›  2   220 ohm resistors (10%)›  1   Atari serial port plug for your computer›  2   5-pin Midi plugs (RCA) for your midi keyboard›  1   breadboard/experimenter perf board›  1   project case›  approx. 10 ft. of 3 wire cable ›  twist ties to tie down wires etc..›  ›  ›  The serial port pins as seen on the computer are:›       ›       2    4   6   8   10   12›        o   o   o   o   o   o  ›      o   o   o   o   o   o   o›      1   3   5   7   9   11  13›  ›       1 - Clock In      7 - Command›       2 - Clock Out     8 - Motor Control›       3 - Data In       9 - Proceed›       4 - Ground       10 - +5V›       5 - Data Out     11 - Audio In›       6 - Ground       12 - +12V       13 - Interrupt›  ›  For this project, we will only need to use pin #'s 3,4,5, and 10 of the›  serial port.›››››››››››››››››››››››››››  ---------------›  (CRUDE)                                    Ground (pin 4)›  SCHEMATIC:      7404                         |›                |\    |\                      2|  ›                | \   | \    220 ohm       5   o   4›  data out   ---|  O--|  O---\/\/\/---------o     o---/\/\/\/-- +5 (pin 10)›  from computer | /   | /                  3 o   o 1›  (pin 5)       |/    |/                  MIDI OUTPUT cable to synth  ›     ›              2›           5  o  4›  Ground---o     o------------(optoisolator)------- data in to computer›          3 o   o 1                                 (pin 3)›       MIDI INPUT cable›        from synth›  ›  Pins 1,3 of the Midi Output cable and pins 1,2,3 of the Midi Input›  cable are not connected.›  ›  The optoisolator is optional, although it is recommended for extra›  protection for your midi keyboard.  I have used the interface ›  hard wired without the optoisolator without any problems (so far).›  ›  Also note: the normal serial i/o to the disk will sometimes interfere›  with the midi interface and vice versa.  This sometimes results in ›  a note sounding on the synth when loading or saving a file, or the›  disk will glitch if you try playing the keyboard during disk i/o.›  One possible way to remedy this annoying problem is to replace›  the 7404 with a tri-state buffer which can be turned to a high-Z state›  using the motor control (pin 8) from the serial port. ›  ›  Anyway, BE CAREFUL and check all your wiring before you hook the ›  interface up to the synthesizer.  ›  ›  Please let me know if you have any suggestions for improving the ›  interface.›  ›  next::  BASIC Midi Recorder Program›       New & Improved Assembly Source Code›  ›  ---------------------------------------------------------------›  Christopher Terpin›  terpin@autarch.acsu.buffalo.edu›  ›                                                                              ›