#define buzzer 2		//定义buzzer I/O number is 7;
#define KEYO 3			//定义key I/O NUMBER IS 2;
#define KEYT 4			//定义key I/O NUMBER IS 2;
int KEY_NUM = 0;		//按键变量赋初值

void BUZZER() {
  for (int i = 0; i < 80; i++) { //输出一个频率的声音
    digitalWrite(buzzer, HIGH); //发声音
    delay(1);//延时1ms
    digitalWrite(buzzer, LOW); //不发声音
    delay(1);//延时1ms
  }
}

void ScanKey() {
  KEY_NUM = 0;
  if (digitalRead(KEYO) == LOW) 			//有按键按下
  { delay(80);
    if (digitalRead(KEYO) == LOW) {
      KEY_NUM = 1; 			//变量设置为1
      while (digitalRead(KEYO) == LOW);			 //等待按键松手
    }
  }

  if (digitalRead(KEYT) == LOW) 			//有按键按下
  { delay(80);
    if (digitalRead(KEYT) == LOW) {
      KEY_NUM = 1; 			//变量设置为1
      while (digitalRead(KEYT) == LOW);			 //等待按键松手
    }
  }
  if (KEY_NUM == 1)
    BUZZER();
}

void setup()
{
  pinMode(KEYO, INPUT_PULLUP); 		//定义keyI/O is INPUT_PULLUP
  pinMode(KEYT, INPUT_PULLUP); 		//定义keyI/O is INPUT_PULLUP
  pinMode(buzzer, OUTPUT); 			//定义buzzer I/O is OUTPUT
  Serial.begin(300);
}
void loop()
{
  ScanKey();			//按键扫描程序，当按键按下时，该子程序会修改key-num的值
}