   // send command packet to RDM880
   RDM880.write(get_readID, 8);
   delay(100);
-  digitalWrite(ledPin, LOW); 
+  digitalWrite(ledPin, LOW);
+  response[7] = NULL;
   standby = true;
-  response[7] = NULL;
-  elapsed_time = 0;
 
   // read response from RDM880 and print
   int i = 0;

    }
    // check for OFF signal
    else if (previousState == HIGH && signalState == LOW) {
      endTime = millis();
      // calculate elapsed time
      return endTime - startTime;
    }
    // no event
    else {
      previousState = signalState;
    }
  }
  return 0;
}



// response packet when idle - 0xAA, 0x00, 0x02, 0x01, 0x83, 0x80, 0xBB
char get_readID[] = { 0xAA , 0x00, 0x03, 0x25, 0x26, 0x00, 0x00, 0xBB };
byte response[11];
const int ledPin = 13;
const int signalPin = 4;
bool standby;
unsigned long elapsedTime;

void setup() {
  Serial.begin(57600);
