Arduino Leonardo as Keyboard (like Makey Makey) using Capacitive Sensor

LeonardoAsCapacitiveKeyboard.ino

#include <CapacitiveSensor.h>
#include <Wire.h>
#include "rgb_lcd.h"
#include "Keyboard.h"

#define NUMBER_OF_KEYS 4
#define KEYBOARD 1
#define TEST 0

int currentMode = 0;
CapacitiveSensor sensors[] = {CapacitiveSensor(6,7), CapacitiveSensor(6,8), CapacitiveSensor(6,9), CapacitiveSensor(6,10)};//, CapacitiveSensor(6,11)};

long threshold[NUMBER_OF_KEYS];

rgb_lcd lcd;

void setup() {

  lcd.begin(16, 2);

  lcd.setRGB(127, 255, 0);

  // Print a message to the LCD.
  lcd.print("Welcome");
  delay(800);
  lcd.clear();
  lcd.print("Setup - Step 1");
  lcd.setCursor(0, 1);
  lcd.print("Don't touch any key");
  for (int i = 0; i < NUMBER_OF_KEYS; i++) {
    //sensors[i] = CapacitiveSensor(6,i + 5)
    long max = 0;
    for (int j = 0; j < 100; j++) {
      long currentValue = sensors[i].capacitiveSensor(30);
      if (max < currentValue)
      max = currentValue;

    }
    threshold[i] = max;
    lcd.clear();
    lcd.print("K");
    lcd.print(i);
    lcd.print(" ");
    lcd.print(threshold[i]);
    delay(50);
    Keyboard.begin();
  }
  //cs_4_2.set_CS_AutocaL_Millis(0xFFFFFFFF);     // turn off autocalibrate on channel 1 - just as an example
  // Serial.begin(9600);
  //Keyboard
}

void loop()
{

  long currentValues[NUMBER_OF_KEYS];
  int margin = analogRead(A0); //variable margin
  margin *= 2;
  for (int i = 0; i < NUMBER_OF_KEYS; i++) {
    //sensors[i] = CapacitiveSensor(6,i + 5);
    long sum = 0;
    for (int j = 0; j < 8; j++) {
      sum += sensors[i].capacitiveSensor(30);
    }
    currentValues[i] = sum / 8;
    //lcd.clear();
    lcd.setCursor((i * 5) % 10, (i * 5) / 10);
    lcd.print("K");
    lcd.print(i);
    lcd.print(" ");
    if (currentValues[i] - threshold[i] > margin) {
      lcd.print("_");
      if (currentMode == KEYBOARD) {
        if (i == 0)
          Keyboard.press(32);
          else
        Keyboard.press(KEY_RIGHT_ARROW + i);
      }
    }
    else
    lcd.print("- ");

  }
  Keyboard.releaseAll();
  lcd.setCursor(11, 1);
  lcd.print(margin);
  if (currentMode == KEYBOARD) {
    lcd.print(" K");
  } else
    lcd.print(" T");

  int buttonReading = digitalRead(4);
  if (currentMode == TEST && buttonReading == 1)
    currentMode = KEYBOARD;
    else if (currentMode == KEYBOARD && buttonReading == 1)
    currentMode = TEST;
  delay(10);
  /*
  //long start = millis();
  long sum = 0;
  for (int i = 0; i < 32; i++) {
  long total1 =  cs_4_2.capacitiveSensor(30);
  sum += total1;
}
long result = sum / 32;
*/
/*
long total2 =  cs_4_6.capacitiveSensor(30);
long total3 =  cs_4_8.capacitiveSensor(30);
*/
//lcd.clear();
//lcd.print(result);
/*
Serial.print(millis() - start);        // check on performance in milliseconds
Serial.print("\t");                    // tab character for debug windown spacing

Serial.print(total1);                  // print sensor output 1
Serial.print("\t");
Serial.print(total2);                  // print sensor output 2
Serial.print("\t");
Serial.println(total3);                // print sensor output 3
*/
delay(50);                             // arbitrary delay to limit data to serial port
}