My other electronics project lately has been a piece of hardware that encapsulates the rhythm algorithm I was working on a couple of weeks ago. The algorithm works surprisingly well, and I think it would make the essence of a great live performance tool. My concept so far is an Arduino-based black box that accepts a MIDI time signal and broadcasts MIDI note messages: a procedural sequencer which leaves the generation of sound signals to an actual drum machine.

I’m still thinking about the front panel layout, which will likely feature a lot of encoders and LED seven-segment displays, but I’ve started working on the MIDI implementation. My in and out circuits are based on this design [see P.P.S.] and my thru circuit is the MIDIbox design. It looks simple, but I’ve never done this before, so I want to take each step individually.

postscript: It works! I have a prototype board set up with MIDI in/out/thru ports one one side, and Vcc/GND/RX/TX on the other. The parts involved, which cost $5.20 from Digikey, are as follows:

• 5x 220Ω resistors
• 1x 47Ω resistor
• 3x DIN-5 PC-mount sockets
• 1x 74HC00 quad nand gate
• 1x 1N914 diode
• 1x 6N138 optocoupler

Post-postscript: The link to the I/O circuit has gone dead since I wrote this, but I’ve since found the official MIDI electrical specification, a complete schematic for a reference MIDI interface implementation.