Cube.Lite

Minim

To do audio analysis, we use the Processing language and IDE, and the Minim library. Minim allows us to open audio files using minim.loadFile(). It also provides the BeatDetect and BeatListener classes that provide real-time audio analysis with its API through these methods:

beatListener.isKick()
beatListener.isSnare()
beatListener.isHat()
beatListener.isOnset(int beat)

We arbitrarily choose to check if every sixth beat is onset, so we would call beatListener.isOnset(5).

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Communication

In order to have Processing communicate with the Arduino, we use Processing's built-in Serial class to establish the connection. All of this goes in the setup() function, in which we extract the portname and connect to it with:

String portName = Serial.list()[1];
myPort = new Serial(this, portName, 9600):
								

Encoding

Each of the four beats (kick, snare, hat and beat onset) corresponds to a certain LED pattern. In order to tell the Arduino which pattern to light up, we encode each type of beat detected as a bit in a 4-bit message. For example, 1100 means there was a kick, a snare, no hat and no sixth beat onset.

Once connected to Serial, each time through draw() the program calls the aforementioned BeatListener methods and if any returns true, it encodes the corresponding bit as 1. This is equivalent to adding the decimal equivalent of that beat type to a sum variable. The logic is as follows:

int msg = 0;

if (beat.isKick()) msg += 1;
if (beat.isSnare()) msg += 2;
if (beat.isHat()) msg += 4;
if (beat.isOnset(5)) msg += 8;

myPort.write(msg.toString() + "x");
								

The suffixed "x" is to signal to the Arduino the end of the message. The Arduino reads this message with Serial.readStringUntil('x').toInt().