3. 버튼으로 LED 켜기

int PIN_LED = 8;
int PIN_BUTTON = 9;

void setup() {
  pinMode(PIN_LED, OUTPUT);
  pinMode(PIN_BUTTON, INPUT);
}

int prevButton = LOW;
int ledOn = LOW;

void loop() {
  int currButton = digitalRead(PIN_BUTTON);
  if(prevButton == LOW && currButton == HIGH) {
    ledOn = HIGH;
  } else if(prevButton == HIGH && currButton == LOW) {
    ledOn = LOW;
  }
  prevButton = currButton;
 
  digitalWrite(PIN_LED, ledOn);
}