void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(8, INPUT_PULLUP);
  pinMode(9, INPUT_PULLUP);
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
}

int s1=0,s2=0, com=0;
long s2start = millis();


void loop() {
  // put your main code here, to run repeatedly:
  if (Serial.available()>0)
    com=Serial.read();

  if (digitalRead(8)==LOW || com=='2') { //代表S2按下
    s2start = millis(); // s2 按下的時間
    digitalWrite(2, HIGH);
    s2=1; // L2 亮
    com=0;
  }

  if (s2==1) { // L2 亮才檢查
    if (millis()-s2start > 5000) {
      s2 = 0;
      digitalWrite(2, LOW);
    }
  }

  if ((digitalRead(9)==LOW && s1==0)|| com=='1') { //P9 按下 且 s1 為0(表第一次按p9)
    if (digitalRead(3)==HIGH) {
      digitalWrite(3, LOW);
    } else {
      digitalWrite(3, HIGH);
    }
    s1=1; // p9 已按下過
    com=0;
  }

  if (digitalRead(9)==HIGH && s1==1) { // p9放開 且 s1==1 表p9被按下過
    s1=0; // p9 已放開
  }

}