I'm currently on project #14 of the Arduino project book.

I'm trying to control a processing sketch on my laptop using my Arduino. This is accomplished by using a potentiometer to control the background of an image.

Arduino code:

void setup(){
  Serial.begin(9600);
}

void loop(){
  Serial.write(analogRead(A0)/4);
}

Processing:

//imports serial library
import processing.serial.*;
//setups the serial object
Serial myPort;
//creates an object for the image
PImage logo;
//variable to store background color
int bgcolor = 0;

void setup(){
  colorMode(HSB,255);
  logo = loadImage("http://arduino.cc/logo.png");
  size(logo.width,logo.height);
  println("Available serial ports");
  println(Serial.list());
  myPort = new Serial(this,Serial.list()[0],9600);
}
//equivalent of arduino's loop function
void draw(){
  if(myPort.available() > 0)
  {
    bgcolor = myPort.read();
    println(bgcolor);
  }

  background(bgcolor,255,255);
  image(logo,0,0);
}

Now, while the code works, and the background color changes as i turn the potentiometer, there is a huge lag between turning the potentiometer and seeing the background change color, and the values from the Arduino/potentiometer change on the processing's serial monitor.

What I've tried:

• Changing the speed of Serial communication

I've noticed that when I decrease the speed of Serial communication, e.g. around 100, the delay between turning the potentiometer and seeing it change on my laptop decreases to about 1 second. However, when I decrease the speed of Serial communication even further, e.g. a value of 1, the delay increases again.

On the flip side, at the standard speed of 9600, the delay is huge, roughly 5sec ++ before the changes in the potentiometer show up on the laptop/processing.

Why does decreasing the communication speed (up to a certain point) decrease the time lag, and increasing it increase the time lag? Also, is there anyway I can make it near instantaneous?