import processing.serial.*; 
 
Serial myPort;    // The serial port
String inString,outString;  
int lf = 13;      // ASCII linefeed 
int  D=1000;
int inv=0;
void setup() { 
  size(400,200); 
  printArray(Serial.list()); 
  myPort = new Serial(this, "COM3", 115200); 
  myPort.bufferUntil(lf); 
} 
 
void draw() { 
  background(0); 
  text("received: " + inString, 10,50); 
  text("Sent: " + inString, 10,100); 
} 
void keyPressed(){
  if (keyCode==UP) D=D/2;
  else if (keyCode==DOWN) D=D*2;
  else if (keyCode==LEFT) D=D/10;
  else if (keyCode==RIGHT) D=D*10;
  outString="S"+D+"E";
  myPort.write(outString);
  } 
void serialEvent(Serial p) { 
  inString = p.readString(); 
  inv=parseInt(inString);
  println(inv);
}