Multiple functions simultaneously in Arduino

Question

I'm working on an Arduino sketch where I created two traffic lights, one for normal traffic and one for pedestrians. I created a function for each of these two lights, which loops it through it's cycle (for example: turn yellow, wait 20 seconds, then turn red and wait again). These are called aTrafficlight() and pTrafficlight, where a is the normal light and p the one for the pedestrians. In my loop() function I set a digitalRead for a button. When this button is pressed the traffic lights should cycle through their loops one at a time (so the normal light turns red, pTrafficlight waits a bit, then turns green, blinks a few times, turns red, waits and ends the loop, so it goes to it's original state.)

This all works. But now I want to add a buzzer. This buzzer must beep once a second while the pTrafficlight is red, once a tenth second while it's green and twice per two seconds while it's flashing green.

Here I encountered a few problems: - When waiting in original state (button's not pressed) it seems I can sometimes press the button without reaction because the loop is still going. I need to figure out how to avoid waiting in the loop when buttonState == LOW. (There's a function wait(int sec)) - When the button is pressed, it loops through the cycles. I could just write some kind of loop implementing the traffic light being red and beeping at the same time, but I'd rather keep these seperated. - Same for the double beeps. I do not want the beeping and flashing of the light to be in the same for loop, as it's confusing and difficult to read and understand the code.

Here's my loop():

int buttonState = 0;

void loop(){
  buttonState = digitalRead(pButton);

  if(buttonState == LOW){
    vSet("red");
    pSet("green");

    // This is where I tried to create the sound.
    digitalWrite(pSound, HIGH);
    delay(10);
    digitalWrite(pSound, LOW);
    wait(1);
  } else {
    aTrafficlight();
    pTrafficlight();
  }
}

Is there a way to solve my problems with multithreading? I tried to look it up at arduino.cc and google, but I can't find a way I understand enough to use it in my existing code.

If not, do you have any better suggestions?

This requires a different programming technique, based on a state machine. It is common in games, google "game loop". Basic hit is en.wikipedia.org/wiki/Game_programming#Game_structure — Hans Passant
– Hans Passant, Commented Feb 2, 2012 at 12:05
Why don't you use interrupts? This way you can invoke an interrupt handler periodically without even having the loop or blocking anything... — Pawel
– Pawel, Commented Feb 3, 2012 at 22:02

Community · Accepted Answer · 2017-05-23 12:11:23Z

3

You don't need multi-threading. You need to use timers, whether via interrupts (as Pawel wrote) or via another mechanism, such as the Metro library, that lets the code continue to loop through while the timer is running. See this question and answer: How Can I Create Interrupts in C for Arduino

Coincidentally, I recently posted some material both on state machines and the Arduino, as Hans Passant mentioned, and on alternatives to delay(), both with additional references you might find useful.

edited May 23, 2017 at 12:11

CommunityBot

11 silver badge

answered Feb 3, 2012 at 22:27

ViennaMike

2,3471 gold badge25 silver badges45 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

JackCColeman · Accepted Answer · 2013-08-13 07:10:20Z

0

You could use a time-slice design. Let me just outline this in very general terms. First code loop so that it always issues a delay(1) and set a mod 10 counter as:

 int stopWhen = -1;  // at startup
 // etc.
 x = (x+1)%10;       // every time loop execs

Then when buttonState == LOW

 if (stopwWhen = -1)
 {
    stopWhen = x;
    // beep etc.
 }

But on every loop:

 // always exec this:
 if (stopWhen == x)
 {
    stopWhen = -1;
    // stop beeping.
 }

answered Aug 13, 2013 at 7:10

JackCColeman

3,8351 gold badge17 silver badges22 bronze badges

Collectives™ on Stack Overflow

Multiple functions simultaneously in Arduino

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related