/***
  Detect rotation of Rotary Encoder by pin2 & pin3
  send rotation state to PC via SerialPort.
  
  CPU: ATMEGA8 16MHz
  Compiler: Arduino 0009 Alpha
  Date: 2007/10/26
  Author: Sho Hashimoto
  WebSite: http://shokai.org
  ***/

char led_pin = 13; // LED on Arduino board
char rot_pinA = 2; // PinA of RotaryEncoder
char rot_pinB = 3; // PinB

void setup()
{
  Serial.begin(9600);
  pinMode(led_pin, OUTPUT);
  digitalWrite(led_pin, HIGH);
  pinMode(rot_pinA, INPUT);
  pinMode(rot_pinB, INPUT);
}

char rot_state;
void loop()
{
  char past_state = rot_state;
  
  // 2つのピンからの入力状態をチェック
  if(digitalRead(rot_pinA)){
    if(digitalRead(rot_pinB)) // HH
      rot_state = 1;
    else // HL
      rot_state = 0;
  }
  else{
    if(digitalRead(rot_pinB)) // LH
      rot_state = 2;
    else // LL
      rot_state = 3;
  }
  
  // 回転方向を割り出す
  if((rot_state+3+1)%3 == past_state){ // 右回り
    Serial.println("R");
  }
  else if((rot_state+3-1)%3 == past_state){ // 左回り
    Serial.println("L");
  }
  
  delayMicroseconds(10);
}