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trying to get an LED to come on for 3 seconds and come off without delay

Former Member

hey guys i'm just trying to get an led to come on for 3 seconds and then comeoff, without using delay, i'm not understanding the millis function but i've tried a bit. kindly let me know what i'm doing wrong. thank you.

 

int count = 0;
long previousMillis = 0;        




long interval = 3000;           


void setup() {
  // set the digital pin as output:
  pinMode(ledPin, OUTPUT);    
  
}


void loop()
{
  
  unsigned long currentMillis = millis();

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


     if (count <=1)
      digitalWrite(ledPin,HIGH);
    else
      digitalWrite(ledPin,LOW);
count ++;
    
    
  }
}

Parents

  • lots of ideas...

    but:

    1. you don't want to write the code twice
    2. and using the % function is ok but it is only clouding the issues

     

    you never said how long you wanted to make the led blink.

    blinking, or oscillation is a repetitive process of turning something on and then off.

    so why not write two loops one count the delay the other controls the state of the led

    FINS

    enjoy

    Cris H.image

     

    #define OFF 0

    #define ON 1

    #define FOREVER for(;;)

    long delay 3000; //msecs

    // set the digital pin as output:

    pinMode(ledPin, OUTPUT);

     

    // we are going to start in the ON state

    int led = ON;

    long millis = 0;

     

    FOREVER {

      

         for( ; millis < delay; millis++ );                              //  this  is the delay loop

              millis = 0;                                      

    // following could have been done differantly by using the =! operator and changing a var name

         if( led == ON ) {                                                  //  switch logic

              led = OFF;

              int LedPin = LOW;}

         else if( led == OFF ){

              led = ON;

               LedPin = HIGH;}

    //  LedPin =! LedPin; // no if() no else if()..

         digitalWrite(ledPin,LedPin);}       // write to the led

  • in reply to phoenixcomm

     

    Interesting insight Cris H.   Unfortunately, your code does not plug into the 'Duino IDE too well.  So, I took some time to create my own completely commented version which I now make available to everyone.  It has been tested and runs on UNO using IDE 0023.


    #define OFF 0

     

    #define ON 1

     

    unsigned long int timecheck;

    unsigned long int mydelay = 3000;  //  3000 msecs = 3 secs

    int ledPin =13;   //  onboard led blinking with a 50 % duty cycle @ 0.166 Hz

                              //  tells user that the program is running normally

     

    int Led = ON;  //  start in the ON state

     

    void setup()

    {

       pinMode(ledPin, OUTPUT);     // config pin for output, duh  image    

       digitalWrite(ledPin,Led);      // initialize state of output pin

       timecheck = millis() + mydelay;       // initialize timecheck 

    }   // putes

     

     

    void loop()

    {

       if (millis() > timecheck) {      // have 3 seconds gone by?

             Led = !Led;      // complement the value  ON or OFF

             digitalWrite(ledPin,Led);  //  update state of output pin

             timecheck = millis() + mydelay;     // update timecheck   

             }  // fi

    // else {

            ;     // other tasks needing to be done between led transistions are placed here

            ;     //  could use a counter to limit number of iterations thru this code subblock

            ;     //  so process returns in time to catch the above timecheck condition.

    //  }  //  esle

     

    }  // pool

  • in reply to billabott

    bill, I was not writing a Duino application. I don't like to spoon feed people.. I just wanted to show how to do the programing logic. one comment about yours thou, is the you created a function mills in the 8 bit arena that is a call (push) and a return (pop) which with limited memory and a slow cpu I would not have done.

    one other thing... I do not like the 'Duino IDE at all. It hides a lot of things. Like the real interrupt structure ( The Select Statement ) and you loose the 30 or 40 years of Leverage with the C library. I use for the Duinos the AVR - Eclipse tools, and I use Eclipse for all my other work as well.

     

    BTW I have been writing with C for few decades at least.

     

    Cris H.

     

    UPDATE I really like your  use of the =! operator.. no muss no fuss. But I didn't know if a nubie would get it so i did it the long way with the two if()s.

Reply Children
  • in reply to R_Phoenix

    R_Phoenix wrote:

     

    http://www.arduino.cc/en/Tutorial/BlinkWithoutDelay

    The sketch I wrote does basicly the same thing but with my personal coding style and flavor.  It is the best I can possibly do.  I like the official arduino tutorial examples because they comment the code extensively.  I believe that my code comments also provide a reasonable justification to adopt it as a basic structure for all sketches.  Who doesn't benefit from a visual indication that the program is alive and doing the tasks assigned to it?  One thing I personally dislike are complicated condition tests,  I try to follow the KISS design philosophy.