int SW_PIN = 4;
int LED_PIN = 5;

void setup(){
  Serial.begin(115200);
  pinMode(SW_PIN,INPUT_PULLUP);
  pinMode(LED_PIN,OUTPUT);
  delay(100);    
}

void loop(){
  if(digitalRead(SW_PIN) == LOW){
    digitalWrite(LED_PIN,HIGH);
    Serial.println("LED HIGH");
    delay(100);
  }else{
    digitalWrite(LED_PIN,LOW);
    Serial.println("LED LOW");
    delay(100);
  }
}