       break;
     case RPI_STAT_BOOT:
       Serial.println("ignore");
-      //起動中はボタンおしても無反応
+      //button is ignored when it's booting
       break;
     case RPI_STAT_RUNNING:
-      //動作中にボタン押すとシャットダウンシーケンススタート
+      //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:
-      //シャットダウン中破はボタンおしても無反応
+      //button is ignored when it's shutting down
       Serial.println("ignore");
       break;
     case RPI_STAT_UNKNOWN:
-      //異常状態になったら、長押しで電源OFF
+      //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();

          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();


  switch(raspi_stat){
    case RPI_STAT_SHUTDOWN:
      //do nothing
      timeout_counter1=0;
      timeout_counter2=0;
      break;
    case RPI_STAT_BOOT:
      //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 ***");
