int pushButton=4;
//引脚2起个名
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
//串口通讯初始化，每秒9600位
pinMode(pushButton, INPUT);
//设置按键引脚为输入
}

void loop() {
  // put your main code here, to run repeatedly:
int buttonState = digitalRead(pushButton);
//读取引脚状态
Serial.println(buttonState);
delay(2);
}