I've been experimenting with processing on both the Arduino UNO and the MEGA 2560. This sketch works on the UNO (except for the additional pins) and trying to get it to work on the MEGA 2560. I've not been able to access the digital pins 22 - 53 on the MEGA. Wondering how to properly address these pins from processing.... using  Standard Firmata 2.2. 

This sketch is a bit of a hack of some of the sample programs in the examples.... grounding an input pin turns on the display in processing.... setting the pin HIGH and then grounding.... avoids floating inputs as when pin is set LOW.

I suppose I should add that it also works on the MEGA analog and PWM pins... can't seem to address the digital pins.

1. import processing.serial.*;
2. import cc.arduino.*;
3. Arduino arduino;
4. color zone = color(150, 50, 150);
5. color zoff = color(50, 50, 50);
6. color back = color(50, 150, 50);
7. color off = color(130, 179, 111);
8. color on = color(50, 45, 100);
9. color bar = color(255, 255, 255);
10. int z;
11. 
    
12. void setup() {
13.   size(670, 880);
14.   arduino = new Arduino(this, Arduino.list()[2], 57600);         // adjust to your com port
15.   PFont font;
16.   font = loadFont("ComicSansMS-18.vlw");            // set to a font that you have
    
17.   textFont(font);
18.   }
19. 
    
20. void draw() {
21.   background(back);
22.   stroke(on);
23.  
24.    for (int i = 2; i <= 12; i++){             // set these pins 2 - 12 as inputs and set high
25.     arduino.pinMode(i, Arduino.INPUT);
26.     arduino.digitalWrite(i, 1);
27.   }
28.  
29.   for (int i = 2; i <= 12; i++) {    
30.      print (i);
31.      print ("  ");
32.      println (arduino.digitalRead(i));           // added for debugging to see if it was writing to the inputs
33.     
34.    
35.     if (arduino.digitalRead(i) == 1){           // changes fill color based on pin status
36.       fill(zoff);
37.     }
38.       else {
39.       fill(zone);
40.     }
41.      
42.     rect(40 + i * 45, 40, 30, 30);                 // input boxes at the top 
43.     rect(120 , 415 + i * 30, 20, 20);              // input boxes at the bottom  with text
44.     fill(bar);
45.     text("Input", 20, 430 + i * 30);
46.     text(i, 80, 430 + i * 30);
47.      }
48.     
49.   for (int i = 0; i <= 4; i++) {                    // graduations on the analog bar display
50.     stroke(bar);
51.     line(165 + i * 50, 140, 165 + i * 50, 380);
52.     stroke(200, 200, 200);
53.     line(140 + i * 50, 150, 140 + i * 50, 370);
54.     color(bar);
55.     fill(bar);
56.     text(20 + i * 20, 150 + i * 50, 410);
57.    }
58.  
59.   for (int i = 2; i <= 12; i++) {               // input numbers on input boxes at the top
60.     fill(200, 200, 200);
61.     text(i, 50 + i * 44, 90);
62.    }
63.  
64.   for (int i = 0; i <= 5; i++) {                   // analog bars with analog reading on top
65.     fill(on);
66.     rect(110, 150 + i * 40,  arduino.analogRead(i) / 4, 20);
67.     text("Analog", 20, 165 + i * 40);
68.     text(i, 80, 165 + i * 40);
69.     fill(200, 150, 150);
70.     text(arduino.analogRead(i)/10.24, 120, 167 + i * 40);
71.     }
72.  
73.   for (int z = 30; z <= 42; z++){                  // for debugging to see if pins 30 - 42 are being written to
74.     arduino.pinMode(z, Arduino.INPUT);
75.     arduino.digitalWrite(z, 1);
76.     print (z);
77.     print ("  ");
78.     println (arduino.digitalRead(z));
79.     }
80. }