byte relayPin[] = {3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19};
byte irPin = 2;
byte relay;
byte relays = sizeof(relayPin) / sizeof(relayPin[0]);

void setup() {
  Serial.begin(115200);
  pinMode(irPin, INPUT);

  for (int i = 0; i < relays; i++) {
    pinMode(relayPin[i], OUTPUT);
  }
}

void loop() {
  unsigned long key = getIrKey();

  switch (key) {
    case 26768: relay =  7; break; // 0
    case 12488: relay =  8; break; // 1
    case  6368: relay =  9; break; // 2
    case 31358: relay = 10; break; // 3
    case  4328: relay = 11; break; // 4
    case 14528: relay = 12; break; // 5
    case 23198: relay = 13; break; // 6
    case 17078: relay = 14; break; // 7
    case 19118: relay = 15; break; // 8
    case 21158: relay = 16; break; // 9
    case 23978: relay =  6; break; // power
    // case  7658: relay = 17; break; // menu
    // case  8918: relay = 18; break; // test
    case   758: relay =  5; break; //  +
    case 15818: relay =  4; break; // back
    case  8168: relay =  3; break; // rew
    case 22448: relay =  2; break; // play
    case 28568: relay =  1; break; // fwd
    case 26528: relay =  0; break; // -

    case 20408: // "C" clear
      for (int i = 0; i < relays; i++)
        digitalWrite(relayPin[i], LOW); // make it low
      key = 0; // do not toggle pin
      break;
    default: key = 0; break; // do not toggle pin
  }

  if (key) {
    if (key < 10000) Serial.print(" ");
    if (key < 1000) Serial.print(" ");
    Serial.print(key);
    Serial.print(" ");
    if (relay < 10) Serial.print(" ");
    Serial.print(relay);
    Serial.print(" ");
    if (relayPin[relay] < 10) Serial.print(" ");
    Serial.print(relayPin[relay]);
    Serial.print(" ");
    Serial.println(digitalRead(relayPin[relay]));
    digitalWrite(relayPin[relay], !digitalRead(relayPin[relay]));
  }
}

int getIrKey() {
  int key = 0, temp;
  int len = pulseIn(irPin, LOW);
  if (len > 3500) {
    for (int i = 1; i <= 32; i++) {
      temp = pulseIn(irPin, HIGH);
      if (temp > 1000)
        key = key + (1 << (i - 17));
    }
  }
  if (key < 0 )
    key = -key;
  return key;
}