 
   switch(raspi_stat){
     case RPI_STAT_SHUTDOWN:
-      //何もしない
+      //do nothing
       timeout_counter1=0;
       timeout_counter2=0;
       break;
     case RPI_STAT_BOOT:
-      //RasPiのGPIOの監視
-      //GPIOがLOWに落とされたら > 監視スクリプトが起動した
+      //Check RasPi's GPIO
+      //GPIO is LOW: "shutdown_checker.py" gets started
       timeout_counter1++;
       if(timeout_counter1 > 20*60*2 ){//50*20 * 60 * 2 (2min)
         Serial.println("*** BOOT error ***");

          int stat = digitalRead(pin_rpistat);
          //Serial.println(stat);
          if(stat == 1){
            shtdwn_delay_count=1; // 電源OFFまでのカウントアップスタート
            Serial.println("start TURN OFF power count down");
            digitalWrite(pin_shutdown,HIGH);
          }
        }else{
          if(shtdwn_delay_count>20*50){ //50*20 * 50 msec (70sec)
            raspi_stat = RPI_STAT_SHUTDOWN;
            Serial.println("*** TURN OFF power successfully ***");
            turn_off();

      break;
    case RPI_STAT_BOOT:
      Serial.println("ignore");
      //button is ignored when it's booting
      break;
    case RPI_STAT_RUNNING:
      //shutdown will start when it's running
      Serial.println("start shutdown process");
      digitalWrite(pin_shutdown,LOW);
      raspi_stat = RPI_STAT_WAIT_SHUTDOWN;
      break;
    case RPI_STAT_WAIT_SHUTDOWN:
      //button is ignored when it's shutting down
      Serial.println("ignore");
      break;
    case RPI_STAT_UNKNOWN:
      //power can be off by long press when status is UNKNOWN
      if(press_duration > 20*3){ //3sec (50*20*3 msec)
        Serial.println("*** Emergency turn off ***");
        turn_off();
