A disk image with Chris Terpin's Home Made MIDI Interface(1991) had been downloaded at some point during the MIDI Blues project and was not examined until now. The disk contained a text file giving a brief (and somewhat incomplete) explanation of how to build the MIDI I/O circuits and hook it up to the SIO port. That was Part 1 of 2, I'm wondering what part 2 of 2 might have said.
This is a message thread in the Forum that contains a link to an FTP site in response #9. Look for "Home Made MIDI Interface.atr". This is where I got my information and software.
The rest of the disk contained the source code for a handler and a BASIC program to test, record and playback the MIDI data. There is a glitch as stated in the text file….."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." There doesn't appear to be anything that would distinguish the MIDI circuits from any other device.
Disclaimer: Do this project at your own risk. I have tried to explain the process to the best of my ability and am reporting my results. I have no idea why yours might be different. Be aware that shorting the wrong wires would be bad for the computer.
Step 1. Build the circuit (or maybe not)
I started to update the ASCII schematic from the text file to Fritzing for clarification. At some point the circuity looked familiar and realized that it was already built on the Arduino MIDI shields. I made the SIO connections to the Shield and gave it a try.
The software worked with both the MIDI shields in my collection.
You can build your own circuit or buy a MIDI breakout board for about $15 plus an SIO cable.
There are just 4 connections that need to be made.
Atari SIO pin:funtion <------>MIDI breakout board(Arduino Prototype Shield)
3:Data input <--------> RX (digital pin 0)
5:Data output<------->TX(digital pin 1)
10: +5volts<----------->+5V or Vcc(+5V)
I chose to setup one of the Arduino prototype boards with the connections to the SIO cable and stackable headers . The Arduino MIDI shields could then be changed at will. (This is not to be used with an Arduino board. Do not attempt to power an Arduino using the SIO port.)
Step 2. Run the software.
Be sure to check your wiring several times before connecting to the SIO port and synthisizer. Run the BASIC program MIDI.BAS. The program will load the handler and then show a menu.
Press T to test the circuit. The computer should play notes through several octives.
If this is working then you need to record some notes before you can play them. You may already know, I don't know how to play the piano so I didn't record any sound files. Just believe me when I tell you it works.
You can save or load the MIDI data but remember the glitch.
Lots of experimentation is yet to be done with this MIDI-to-SIO setup. Right now there are several MIDI related disks that have remained unopened. I hope to find something of interest after I clean up the work table.
Chris, if you are out there, PM me. I think I owe you a lunch.