Arduino Programming – Interval

How to write a program that fires actions with different intervals without using the delay() function. Configuration of the serial port and printing values is also explained.

Level : beginner with Arduino. ( Basic knowledge of programming principles like if/else and variables ).

Download the Arduino ( .pde ) files : arduino_tutorial_interval.zip

Interval_basic.pde :

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/*

  Print serial text with an interval.

  Basic example.   

  

  created 01-12-2009 by kasperkamperman.com

*/



unsigned long previousMillis  = 0;

unsigned long currentMillis   = 0;



int interval = 1000;



void setup() {

  // opens serial port, sets data rate to 57600 bits per second

  Serial.begin(57600);   

}



void loop()

{ // save number of milliseconds since the program started

  currentMillis = millis();

  

  // check to see if the interval time is passed. 

  if (currentMillis - previousMillis >= interval == true ) {

    

      Serial.print("this program runs now for : ");

      Serial.print(currentMillis);

      Serial.println(" milliseconds");

      

      // save the time when we displayed the string for the last time

      previousMillis = currentMillis;

  }

}

Interval_for_loop.pde :

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/*

  Print serial text with different intervals.   

  Check the array with a for-loop.

  

  created 01-12-2009 by kasperkamperman.com

*/



const int amountOfIntervals = 3;



unsigned long previousMillis[amountOfIntervals]  = {0, 0, 0};

unsigned long currentMillis                      = 0;



int intervals[amountOfIntervals]       = {1000, 2500, 5000};



void setup() {

  // opens serial port, sets data rate to 57600 bits per second

  Serial.begin(57600);   

}



void loop()

{ // save number of milliseconds since the program started

  currentMillis = millis();

  

  // check the 3 intervals one by one with a for-loop. 

  for(int i=0; i<amountOfIntervals; i++) {

    

    // check to see if the interval time is passed.  

    if (currentMillis - previousMillis[i] >= intervals[i]) {

      

      if(i==0) Serial.println("-   every 1 second");

      if(i==1) Serial.println(" -  every 2.5 second");

      if(i==2) Serial.println("  - every 5 seconds");

      

      // save the time when we displayed the string for the last time

      previousMillis[i] = currentMillis; 

            

    }

  }

}