P-Comp: Sine Wave of Doom AKA the Poser Theremin

In this week’s lab, we learned about Serial Duplex and continued to learn more about how to get Arduino and Processing to talk to each other.

In my spin on the lab, I hooked up 2 potentiometers through the Arduino to control the frequency and panning of a sine wave in Processing that is manifested on screen and as audio.  I don’t know why I chose red and blue for the sine waves.  Maybe I’ve been watching too much TV coverage of the presidential campaign.  In any case, the effect is that of a sine wave of doom or a poser theremin.

To get Processing to play sound, I used the Minim library.  I basically poached some example code from the Minim site and tweaked it so the sound responds to analog ins from the Arduino instead of mouseX and Y in the original sketch.


I hope to use more exciting sensors later on to make it more expressive and musical when I get back from fall break next week, but it took me awhile to tweak the software side of things and the computer store was already closed by the time I got around to this. Here it is in action:

My digital camera didn’t pick up the audio very well, so here is an MP3 of some “music” I made.  And here is another attempt.

And finally, here is the Processing code:

import processing.serial.*;     // import the Processing serial library
import ddf.minim.*;
import ddf.minim.signals.*;

Serial myPort;                  // The serial port
AudioOutput out;
SineWave sine;
int sensors[] = new int[2];

int passX;
int passY;

void setup(){
myPort = new Serial(this, Serial.list()[0], 9600);
size(512, 200);
// always start Minim before you do anything with it
// get a line out from Minim, default sample rate is 44100, bit depth is 16
out = Minim.getLineOut(Minim.STEREO, 512);
// create a sine wave Oscillator, set to 440 Hz, at 0.5 amplitude, sample rate 44100 to match the line out
sine = new SineWave(440, 0.5, 44100);
// set the portamento speed on the oscillator to 200 milliseconds
// add the oscillator to the line out
passX = 0;
passY = 0;

void draw()
// draw the waveforms
for(int i = 0; i < out.left.size()-1; i++)
stroke(#FF0000); //left is red
line(i, 50 + out.left.get(i)*50, i+1, 50 + out.left.get(i+1)*50);
stroke(#0023FC); //right is blue
line(i, 150 + out.right.get(i)*50, i+1, 150 + out.right.get(i+1)*50);
float freq = map(passY, 0, 1023, 1500, 60);
// pan always changes smoothly to avoid crackles getting into the signal
// note that we could call setPan on out, instead of on sine
// this would sound the same, but the waveforms in out would not reflect the panning
float pan = map(passX, 0, 1023, -1, 1);

void stop()

void serialEvent(Serial myPort)
// read the serial buffer:
String myString = myPort.readStringUntil(‘\n’);
myString = trim(myString);
int sensors[] = int(split(myString, ‘,’));
for (int sensorNum = 0; sensorNum < sensors.length; sensorNum++)
// print(“Sensor ” + sensorNum + “: ” + sensors[sensorNum] + “\t”);
passX = sensors[0];
passY = sensors[1];
//print(“PassX= ” + passX + “, PassY= ” + passY);


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