// Includes
import processing.serial.*;

Serial port;

// Constants
int i;
int lf = 10;
long last;

void setup() 
{ 
  size(800, 600);
  rectMode(CENTER);
  noStroke();
  fill(0);
  background(255);

  // Print a list in case COM1 doesn't work out
  println("Available serial ports:");
  println(Serial.list());
  
  port = new Serial(this, Serial.list()[0], 9600);
  port.bufferUntil(lf); 
  i=0;
} 
 
void draw() 
{ 
  if(millis()-last>500) { 
//   background(255);
    i=0;
  }
}

float oldval, newval;

void serialEvent(Serial p) {   
  String inString = (port.readString()); 
  i=(i+1)%53;
  oldval=newval;
  newval = parseFloat(inString);
  float val = abs(newval-oldval);
  stroke(255,0,0);
  fill(val/1024.0*255);
  rect(i*15, height, 15,val/1024.0*-1.0*1200.0);
  last=millis();
}

void keyPressed() {
  background(255);
}