Arduino millis()函数

此函数用于返回的Arduino板开始运行当前程序时的毫秒数。这个数字在大约50天后溢出，即回到零。
善于使用millis能使Arduino实行多线程

unsigned long time; 
void setup() { 
   Serial.begin(9600); 
} 
 
void loop() { 
   Serial.print("Time:"); time = millis();
   //prints time since program started
   Serial.println(time); 
   // wait a second so as not to send massive amounts of data
   delay(1000); 
}