from processing to arduino mega 2560 doesn't work

Projects Interfacing w/ Software on the Computer
1

process code:

import processing.serial.*;

Serial myPort;  // Create object from Serial class

void setup() 
{
  size(200,200); //make our canvas 200 x 200 pixels big
  String portName = Serial.list()[0]; //change the 0 to a 1 or 2 etc. to match your port
  myPort = new Serial(this, portName, 9600);
}
void draw() {
  if (mousePressed == true) 
  {                           //if we clicked in the window
   myPort.write('1');         //send a 1
   println("1");   
  } else 
  {                           //otherwise
  myPort.write('0');          //send a 0
  }   
}

arduino sode :

char val; // Data received from the serial port
 int ledPin = 13; // Set the pin to digital I/O 13
  void setup() {
   pinMode(ledPin, OUTPUT); // Set pin as OUTPUT
   Serial.begin(9600); // Start serial communication at 9600 bps
 }
  void loop() {
   if (Serial.available()) 
   { // If data is available to read,
     val = Serial.read(); // read it and store it in val
   }
   if (val == '1') 
   { // If 1 was received
     digitalWrite(ledPin, HIGH); // turn the LED on
   } else {
     digitalWrite(ledPin, LOW); // otherwise turn it off
   }
   delay(10); // Wait 10 milliseconds for next reading
}

when i start on UNO, it does work. (mouse click -> LED on)

but when i start on MEGA 2560, it doesn't work. (no action -> LED on always)

so i types serial monitor 1 or 0, that work ON and OFF properly

why so from processing to arduino doesn't work?

problem on MEGA?

2

If it works from the Serial Monitor the Arduino code is fine. And it is very short and simple.

I don't know Processing. Is it possible it is not using the correct serial port?

...R

3

YES when i used UNO, i use corret serial port. so, only when mouse pressed, then LED light ON. LED is pluged arduino PIN 13. of course when no pressed, LED off.
but i use MEGA 2560, whenever mouse pressed or not, LED light on always after processing code upload.

4 
  String portName = Serial.list()[0]; //change the 0 to a 1 or 2 etc. to match your port

How many ports are in the list? Is the Arduino actually connected to the first entry in the list?

If you switch boards, you also switch ports.