How to Use Enum in Arduino: Simple Guide with Examples

In Arduino, use enum to create a list of named integer constants that make your code easier to read and manage. Define an enum with names for values, then use those names in your code instead of numbers.

Syntax

An enum groups related named integer constants under one type. You start with the keyword enum, give it a name, and list the names inside curly braces. Each name represents a number starting from 0 by default.

Example parts:

• enum: keyword to define the group
• Status: the name of the enum type
• { OFF, ON, ERROR }: named constants inside the enum

arduino

enum Status {
  OFF,    // 0
  ON,     // 1
  ERROR   // 2
};

Example

This example shows how to define an enum for LED states and use it to control an LED on pin 13. It prints the current state to the Serial Monitor.

arduino

enum LedState {
  OFF,
  ON,
  BLINK
};

LedState currentState = OFF;

void setup() {
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  switch (currentState) {
    case OFF:
      digitalWrite(13, LOW);
      Serial.println("LED is OFF");
      currentState = ON;
      break;
    case ON:
      digitalWrite(13, HIGH);
      Serial.println("LED is ON");
      currentState = BLINK;
      break;
    case BLINK:
      digitalWrite(13, HIGH);
      delay(250);
      digitalWrite(13, LOW);
      delay(250);
      Serial.println("LED is BLINKING");
      currentState = OFF;
      break;
  }
  delay(1000);
}

Output

LED is OFF
LED is ON
LED is BLINKING
LED is OFF
LED is ON
LED is BLINKING
...

Common Pitfalls

Common mistakes when using enum in Arduino include:

• Not ending the enum definition with a semicolon ;.
• Using enum names without specifying the enum type variable.
• Assuming enum values start at 1 instead of 0.
• Assigning values outside the enum without casting.

Always remember to declare variables of the enum type to use the named constants properly.

arduino

/* Wrong: missing semicolon */
enum Color {
  RED,
  GREEN,
  BLUE
};  // <-- added semicolon here

/* Right: with semicolon */
enum Color {
  RED,
  GREEN,
  BLUE
};

/* Wrong: using enum names without variable */
// digitalWrite(13, RED); // error

/* Right: declare variable */
Color ledColor = RED;
// digitalWrite(13, ledColor); // works if ledColor matches pin logic

Quick Reference

Concept	Description	Example
Define enum	Create named integer constants	enum Mode { AUTO, MANUAL, OFF };
Default values	Start at 0, increment by 1	AUTO=0, MANUAL=1, OFF=2
Assign custom values	Set specific numbers	enum Mode { AUTO=1, MANUAL=5, OFF=10 };
Use enum variable	Store enum values	Mode current = AUTO;
Switch with enum	Control flow with enum	switch(current) { case AUTO: ... }

Key Takeaways

Use enum to name related integer constants for clearer Arduino code.

Always end enum definitions with a semicolon ;.

Enum values start at 0 by default but can be set manually.

Declare variables of the enum type to use the named constants properly.

Use enums in switch statements for clean control flow.