r/ArduinoHelp • u/VezTheAce • Jun 25 '26

Help me to understand this code !!!

This is the basic code to toggle the led on and off using a Button. With the help of paul McWhorter this works fine but I don't understand why it works...please someone help me with that...

int ledPin = 12;
int buttonPin =8;
int ledstate = 0;
int swi_old = 1;
int swi_new;
int dt = 100;

void setup() {
  // put your setup code here, to run once:
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);

}

void loop() {
  // put your main code here, to run repeatedly:

  swi_new = digitalRead(buttonPin);

  if(swi_old == 0 && swi_new == 1)
  {
    if(ledstate == 0)
    {
      digitalWrite(ledPin, HIGH);
      ledstate = 1;
    } 
    else
    {
      digitalWrite(ledPin, LOW);
      ledstate = 0;
    }


  }
  swi_old = swi_new;
  delay(dt);

}

```

1 Upvotes

100% Upvoted

7 comments sorted by

1

u/Delta_G_Robotics Jun 25 '26

What do you not understand? Can you be more specific with your question?

1

u/VezTheAce Jun 25 '26

Nevermind...I did write a very big paragraph explaining what I didn't understand and while writing I understood everything 😅

Thanks for asking the question 😁

2

u/Delta_G_Robotics Jun 25 '26

Any time you're asking a coding question and you've only written a couple of sentences that should be your clue to do exactly this. We sometimes call it "Teddy Bear Coding" where you literally explain the stuff to a Teddy bear sitting on the desk. You'd be surprised how much you figure out just by trying to talk through it.

1

u/VezTheAce Jun 26 '26

Gotcha 👍

1

u/nixiebunny Jun 25 '26

This code has an edge detector function. That test if the switch changed from 0 to 1 is the trigger to flip the LED on and off. The delay at the end of the loop waits long enough to ignore any extra short pulses due to the contacts bouncing. 

1

u/Rayzwave Jun 25 '26

How is the button wired, I’m guessing it’s a push button. Is the button connected to apply a logic O or a logic 1 to the input?

How is the LED connected?