Arduino学习—— 蜂鸣器

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(2,OUTPUT);
  pinMode(7,OUTPUT);
  analogWrite(9,255);
}

void loop() {
  // put your main code here, to run repeatedly:
  //Serial.println(digitalRead(4));
  if(digitalRead(4)==0){
    digitalWrite(2,1);
    digitalWrite(9,255);
    digitalWrite(7,HIGH);
    delay(1);
    digitalWrite(7,LOW);
    delay(1);
  }else{
    digitalWrite(2,0);
    digitalWrite(9,0);
    digitalWrite(7,0);
  }
}