Everything for Electronics
Posted in: Developing Perspectives (September 2011)

Putting A Pretty Face On Your Next Project

By Bryan Bergeron

One approach is to build your own touch-screen interface using a screen from a discarded Nintendo DS or Chumby. Another is to use a touch shield for the Arduino, such as the capacitive touch interface shield available from SparkFun. However, this alternative lacks the visual feedback that’s commonly associated with touch-screens.

I think that the best approach to acquiring a slick interface is to repurpose one of the many interface devices that support MIDI — the Musical Instrument Digital Interface. You’ll find an abundance of inexpensive, easily repurposed MIDI interfaces designed for musicians listed on the Web. If you’re working with audio — including analog-to-digital conversion and remote, audio-based switching — then going the MIDI route is a no-brainer.

Although the MIDI standard or protocol has been around since the early 1980s, it continues to enable modern electronic gadgets. For example, just about every computer compatible keyboard or synthesizer has MIDI input and output. I have a MIDI guitar, as well as an electronic drum set that are both MIDI devices. In addition, I recently purchased several apps for my iPad that work with MIDI hardware.

Connecting a MIDI device to a standard PC or Mac is as simple as purchasing a $5 MIDI to USB cable. Unfortunately, the equivalent cable for the iPad is about $40. I assume the cables for Android-based tablets are more reasonable.

Many MIDI-compatible control surfaces designed for musicians can be used for a variety of projects without modification. If you search for ‘MIDI Controller’ on the Web, you’ll also find dozens of sub-$50 MIDI to USB keyboards and percussion interfaces. Some interfaces cost considerably more, depending on their functionality. For example, I’ve been working with the Korg Kaoscillator Pro ($400) — a music synthesizer that doubles as a graphic MIDI controller. The tabletsized device transmits numerical MIDI codes as a function of rubbing, stroking, or tapping the 8 x 8 LED grid with a finger. Then, there’s the more affordable Novation Launchpad ($150) — a dedicated MIDI controller with a similar 8 x 8 grid user interface. If your interface needs are more toward traditional sliders and faders, then there’s the Numark DJ2GO controller ($60). All three interfaces connect to a computer via USB.

How you enable your projects with these interfaces is up to your imagination. With the addition of a microcontroller, just about anything is possible. For example, I’ve used a Korg MIDI controller and an Arduino-intermediary to control a graphical program that I wrote in Processing on my PC. If you check the Arduino site, you’ll see that ‘talking MIDI’ is a simple two-wire serial communications protocol affair. Of course, just about any microprocessor will do, as long as it can keep up with the 31.25K bps communications rate.

I’ve had great luck with the inexpensive, high speed Arduino Mega clone — ChipKit Max32 ($50) — from Digilent. If you’re new to MIDI and the numerous options available for controlling your next project seem overwhelming, then check out the tutorials on the Arduino site (arduino.cc). You should also consider the MIDI shields and breakout boards, and documentation on the MIDI boards available from SparkFun ([url=http://www.sparkfun.com]http://www.sparkfun.com[/url]). It also wouldn’t hurt to spend an hour in your local music store to see how the various MIDI tools work in their intended environments. NV