Moving line graph


Currently im working on a project to control an arduino with processing.
The serial communication is going fine but i cant seem to find any good way to put waveforms into a moving line graph. I have looked at some libraries but cant wrap my head around on how to move them…
Any help would be appreciated :slight_smile:


Did you look this Minim exemple ?
[](http://Minim AudioPlayer)

Thanks for the reply,
the minim library is for processing audio and the only thing i get from the arduino are separate values…
So how would that be useful? can you maybe give me some example code?

I think he just did! :wink: You’ll want to store the discrete values you get into your own form of buffer though - perhaps using Reference /

I’s sorry if im just being stupid here but when i try to use an IntList it gives me a nullPointerExeption.
I changed the minim functions to the IntList functions because if i didnt do that it would also give me an error “The function “bufferSize()” does not exist”.

Here is my code:

import processing.serial.*;
import ddf.minim.*;

Minim minim;
Serial myPort;
boolean firstContact = false;  
int serialCount = 0;  
int[] serialInArray = new int[2];
int inByte;
IntList sineValue;

void setup()
  size(512, 200, P3D);
  myPort = new Serial(this, Serial.list()[1], 9600);
  // we pass this to Minim so that it can load files from the data directory
  minim = new Minim(this);

void draw()

  // draw the waveforms
  // the values returned by left.get() and right.get() will be between -1 and 1,
  // so we need to scale them up to see the waveform
  // note that if the file is MONO, left.get() and right.get() will return the same value
  for (int i = 0; i < sineValue.size() - 1; i++)
    float x1 = map( i, 0, sineValue.size(), 0, width );
    float x2 = map( i+1, 0, sineValue.size(), 0, width );
    line( x1, 50 + sineValue.get(i)*50, x2, 50 + sineValue.get(i+1)*50 );
    line( x1, 150 + sineValue.get(i)*50, x2, 150 + sineValue.get(i+1)*50 );

void serialEvent(Serial myPort) {

  inByte =;

  if (firstContact == false) {
    if (inByte == 'A') {
      myPort.clear();          // clear the serial port buffer
      firstContact = true;     // you've had first contact from the microcontroller
      myPort.write('A');       // ask for more
  } else {
    serialInArray[serialCount] = inByte;

    if (serialCount > 0 ) {


      // Send a capital A to request new sensor readings:
      // Reset serialCount:
      serialCount = 0;

Does anyone have an idea?

You have to initialize your sineWave/IntList. Either you just declare it as IntList sineWave = new IntList(); or you initialize it in setup() with sineWave = new IntList();

When something gives a nullpointer, always check if you initialized it correctly, before going through millions of lines of code :wink: