Turning LED on / off virtually using processing

LEDonoff-stepresponse

 import processing.serial.*;
 
  
Serial myPort;  // Create object from Serial class
int val;      // Data received from the serial port
int sensorData; // Data received from the serial port with 1,2,3,4 framing numbers filtered out
int low = 0;
int med = 0;
int high = 0;
float value1 =0;
float value2 =0;

int byte1 = 0;
int byte2 = 0;
int byte3 = 0;
int byte4 = 0;

int up_low = 0;
int up_high = 0;
int down_low = 0;
int down_high = 0;

float x = 640;      // Circle parameters
float y = 400;
float radius = 100;

PImage img1;       
PImage img2;


void setup()
{
  size(1280, 760);
  // I know that the first port in the serial list on my mac
  // is always my FTDI adaptor, so I open Serial.list()[0].
  // On Windows machines, this generally opens COM1.
  // Open whatever port is the one you're using.
  myPort = new Serial(this, "/dev/tty.usbserial-A9024P2C", 9600);
  img1 = loadImage("ledoff.jpg"); // Take images that were imported to the sketch before
  img2 = loadImage("ledon.jpg");
}
 
void draw()
{
  while (myPort.available() > 0) {    // If data is available
    byte1 = byte2;
    byte2 = byte3;
    byte3 = byte4;
    byte4 = up_low;
    up_low = up_high;
    up_high = down_low;
    down_low = down_high;
    down_high = myPort.read();
 
    if ((byte1 == 1) & (byte2 == 2) & (byte3 == 3) & (byte4 == 4)){                // Filter out the framing numbers: 1,2,3,4
       
       float up_value = 256*up_high + up_low;
       float down_value = 256*down_high + down_low;
       
       value1 = (up_value + (1023 - down_value))/2.0;
       
       println("VALUE1 IS " + value1); //print to the screen
     
 
    }
   
     if ( value1 >= 0 && value1 < 1700 )  {  // If nothing touching step response sensor
     image(img2, 0, 0);                     // show image with LED off

  } else if ( value1 > 1700 )  {   // If you touch step response sensor and increase values received,
     image(img1, 0, 0);            // show image with LED on
  }
  }
}