Infrared Dedicated Decoder

/*
  IR remote control (Sony) detection for Arduino, M. Burnette
  Binary sketch size: 2,794 bytes (of a 8,192 byte maximum)

  ☺  20130103 MRB Modified for interface to Mega2560
      Europa codebase for menu system
      
  ☺  20121230 MRB Modified for Tiny85 Google Tiny library
      Tiny85 Internal RC 16MHz

  ☺  20121230 MRB modifications to adapt to numeric input, avoid dupes,
      and to generally "behave" consistently
  ☺  Used with Electronic Goldmine IR detector MIM 5383H4
      http://www.goldmine-elec-products.com/prodinfo.asp?number=G16737
  ☺  IR detector:
      Pin 1: To pin D4 on Arduino ATtiny85
      Pin 2: GND
      Pin 3: 5V through 33 Ohm resistor
  
  ☺  This is based on pmalmsten's code found on the Arduino forum from 2007:
      http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1176098434/0

*/
// Pins 2/3 used for Software serial
int irPin     = 4;       //Sensor pin 1 wired to Arduino's pin D4
int statLED   = 0;       //Toggle the status LED every time Power is pressed
int start_bit = 2200;    //Start bit threshold (Microseconds)
int bin_1     = 1000;    //Binary 1 threshold (Microseconds)
int bin_0     = 400;     //Binary 0 threshold (Microseconds)

void setup() {
  pinMode(statLED, OUTPUT);
  digitalWrite(statLED, LOW);

  pinMode(irPin, INPUT);

  Serial.begin(9600);
  Serial.println("IR/Serial Initialized: ");
}

void loop() {
  int key = getIRKey();   //Fetch the key
  
  if(key != 0)            //Ignore keys that are zero
  {
    switch(key)
    {
      case 128: Serial.print("1"); break;
      case 129: Serial.print("2"); break;
      case 130: Serial.print("3"); break;
      case 131: Serial.print("4"); break;
      case 132: Serial.print("5"); break;
      case 133: Serial.print("6"); break;
      case 134: Serial.print("7"); break;
      case 135: Serial.print("8"); break;
      case 136: Serial.print("9"); break;
      case 137: Serial.print("0"); break;
      
      case 144: Serial.print("A"); break;  // CH Up
      case 145: Serial.print("B"); break;  // CH Down
      case 146: Serial.print("C"); break;  // VOL Right
      case 147: Serial.print("D"); break;  // VOL Left
      case 148: Serial.print("E"); break;  // Mute
      case 165: Serial.print("F"); break;  // AV/TV
      case 149: Serial.print("P");         // Power == MENU ACTIVE
        //This toggles the statLED every time power button is hit
        if(digitalRead(statLED) != 1)
          digitalWrite(statLED, HIGH);
        else
          digitalWrite(statLED, LOW);
        break;

      //default: Serial.println(key); // for inspection of keycode
    }

    delay(400);    // avoid double key logging (adjustable)
  }
}

int getIRKey() {
  int data[12];
  int i;

  while(pulseIn(irPin, LOW) < start_bit); //Wait for a start bit
  
  for(i = 0 ; i < 11 ; i++)
    data[i] = pulseIn(irPin, LOW);      //Start measuring bits, I only want low pulses
  
  for(i = 0 ; i < 11 ; i++)             //Parse them
  {	    
    if(data[i] > bin_1)                 //is it a 1?
      data[i] = 1;
    else if(data[i] > bin_0)            //is it a 0?
      data[i] = 0;
    else
      return -1;                        //Flag the data as invalid; I don't know what it is! Return -1 on invalid data
  }

  int result = 0;
  for(i = 0 ; i < 11 ; i++)             //Convert data bits to integer
    if(data[i] == 1) result |= (1<<i);

  return result;                        //Return key number
}