02. Blink Code

Did you know that Arduino UNO board has a inbuilt LED connected to its GPIO 13 pin.
Lets program Arduino to blink that LED, if you wish to connect an external LED,schematics given below:

• Arduino has an extensive set of examples. Go to Files->Examples->0.1 Basics->Blink
  
• If your too lazy then just copy paste the code below
  

//Taken from https://www.arduino.cc/en/Tutorial/Blink

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

Explanation :

• pinMode(pin_number,OUTPUT (or) INPUT) -This function specifies the compiler if the pin number(13 in this case) is going to be used for output or Input (Output for driving LED's).
  
• digitalWrite(pin_number,HIGH(or)LOW) - This function writes HIGH or LOW to the pin_number (13 in this case).f the pin has been configured as an OUTPUT with pinMode(), its voltage will be set to the corresponding value: 5V for HIGH, 0V (ground) for LOW.
  
• delay(ms) -Pauses the program for the amount of time (in milliseconds) specified as parameter. (There are 1000 milliseconds in a second.)