Difference between revisions of "Lesson 21--Microduino "Use Timer Interrupt""

// LED connects to Pin 13
#include <MsTimer2.h>               //Timer's head file

void flash()                        //The interrupt service function
{                        
  static boolean output = HIGH;
  digitalWrite(13, output);
  output = !output;
}
void setup()
{
  pinMode(13, OUTPUT);
  MsTimer2::set(500, flash);        //Set interrupt function, the timer is 500ms
  MsTimer2::start();                //Start timer
}

void loop()
{
}

unsigned long ledOn=500,ledOff=500; //Define the timer 500ms
int ledStatus;                      //Define LED state, HIGH or LOW
void setup()
{
	pinMode(13,OUTPUT);
	digitalWrite(13,HIGH);
	ledStatus=HIGH;
}
void loop()
{
    unsigned long nowtime=millis(); //Get the system current runned time
    if(ledStatus==HIGH)             //Check LED state
    {
      if(nowtime>ledOn)             //Check if time out happened
      {
        ledOn=nowtime;              //Record time, the first time is 500ms
        ledOff=nowtime+500;         //Calculate next time when LED state change
        digitalWrite(13,LOW);       //LED off
        ledStatus=LOW;              //Record current LED state, used next time     
    }
}

else{      
	if(nowtime>ledOff)
	{   
		ledOff=nowtime;
		ledOn=nowtime+500;
		digitalWrite(13,HIGH);
		ledStatus=HIGH;
	}
}
}