Alright, in the last article, we set up the IDE to compile and run code for ESP32 board. We wrote a simple code to blink the built-in LED.

Now, we will learn about the basic structure of the code.

Below is the code that we will understand.

void setup() {
  // put your setup code here, to run once:

}

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

This is the bare minimum code that ESP32 needs.

This is C Language, means the code is executed from top to bottom, left to right.

But these are function definitions, there is no function calling that we see in this code. It means, there is something going on behind the scenes and calling these functions.

So, how it works is it will call the setup function first, and then it will continuously call the loop function.

Previous code

Let's see the code from the previous article.

int ledPin = 2;

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

void loop() {
  // put your main code here, to run repeatedly:
  digitalWrite(ledPin, HIGH);
  delay(1000);
  digitalWrite(ledPin, LOW);
  delay(1000);
}

First, we have a variable ledPin with value 2 because on our board, it is the pin 2, that is connected to the built-in LED.

Then it will call setup function initially and only once.

In this function, we have just a single line of code.

pinMode(ledPin, OUTPUT); This means, the mode of ledPin (that is pin 2), will be output mode. It means we decide, if we want to power this pin or not (e.g., HIGH or LOW).

Then we have loop function, which will be called continuously.

digitalWrite(ledPin, HIGH); means power the ledPin (pin 2).

Then delay(1000); means wait for 1000ms (or 1 second).

Then, similarly, digitalWrite(ledPin, LOW); to stop powering the pin 2.

Then again, wait for 1 second.

And everything inside the loop function will repeat. So the LED will blink, on and off with 1 second interval.

Easy!