Control Statements

Control statements in Arduino are used to control the flow of execution in a program.

They allow you to make decisions, repeat actions, and manage program logic based on certain conditions or loops.

This tutorial covers the main control statements in Arduino, with examples to illustrate their usage.

Table of Contents

1. What Are Control Statements?

Control statements manage the execution flow of a program. They allow you to:

• Make decisions based on conditions.
• Repeat a block of code multiple times.
• Break or skip iterations in loops.

2. Types of Control Statements

1. Conditional Statements: Execute code blocks based on specific conditions (if, else, switch).
2. Looping Statements: Repeat code blocks until a condition is met (for, while, do-while).

3. Conditional Statements

3.1 if and else

The if statement executes a block of code if the condition is true. The else block executes if the condition is false.

Syntax

if (condition) {
  // Code to execute if condition is true
} else {
  // Code to execute if condition is false
}

Example: Turn LED On Based on Button Press

const int buttonPin = 2;
const int ledPin = 13;

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int buttonState = digitalRead(buttonPin);

  if (buttonState == HIGH) {
    digitalWrite(ledPin, HIGH); // Turn LED on
    Serial.println("LED ON");
  } else {
    digitalWrite(ledPin, LOW);  // Turn LED off
    Serial.println("LED OFF");
  }
}

3.2 switch Case

The switch statement selects one of many code blocks to execute based on a variable’s value.

Syntax

switch (variable) {
  case value1:
    // Code to execute for value1
    break;
  case value2:
    // Code to execute for value2
    break;
  default:
    // Code to execute if no case matches
    break;
}

Example: Control LED Brightness Using a Switch

const int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int mode = 2; // Change mode for different brightness levels

  switch (mode) {
    case 1:
      analogWrite(ledPin, 64); // Low brightness
      break;
    case 2:
      analogWrite(ledPin, 128); // Medium brightness
      break;
    case 3:
      analogWrite(ledPin, 255); // High brightness
      break;
    default:
      analogWrite(ledPin, 0); // LED off
      break;
  }

  delay(1000);
}

4. Looping Statements

4.1 for Loop

The for loop is used to repeat a block of code a specific number of times.

Syntax

for (initialization; condition; increment) {
  // Code to execute
}

Example: Blink LED 10 Times

const int ledPin = 13;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  for (int i = 0; i < 10; i++) {
    digitalWrite(ledPin, HIGH);
    delay(500);
    digitalWrite(ledPin, LOW);
    delay(500);
  }
  while (true); // Stop further execution
}

4.2 while Loop

The while loop executes a block of code as long as the condition is true.

Syntax

while (condition) {
  // Code to execute
}

Example: Blink LED While Button Is Pressed

const int buttonPin = 2;
const int ledPin = 13;

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  while (digitalRead(buttonPin) == HIGH) {
    digitalWrite(ledPin, HIGH);
    delay(500);
    digitalWrite(ledPin, LOW);
    delay(500);
  }
}

4.3 do-while Loop

The do-while loop executes the code block at least once before checking the condition.

Syntax

do {
  // Code to execute
} while (condition);

Example: Print Numbers Until 10

void setup() {
  Serial.begin(9600);

  int count = 1;
  do {
    Serial.println(count);
    count++;
  } while (count <= 10);
}

void loop() {
  // Empty
}

5. Break and Continue

5.1 Break

• Terminates the current loop or switch statement.

Example: Stop Loop After 5 Iterations

void setup() {
  Serial.begin(9600);

  for (int i = 1; i <= 10; i++) {
    if (i > 5) {
      break;
    }
    Serial.println(i);
  }
}

void loop() {
  // Empty
}

5.2 Continue

• Skips the rest of the current iteration and moves to the next iteration.

Example: Skip Even Numbers

void setup() {
  Serial.begin(9600);

  for (int i = 1; i <= 10; i++) {
    if (i % 2 == 0) {
      continue;
    }
    Serial.println(i);
  }
}

void loop() {
  // Empty
}

6. Practical Examples

Example 6.1: LED Chase Sequence

const int ledPins[] = {2, 3, 4, 5};
const int numLeds = 4;

void setup() {
  for (int i = 0; i < numLeds; i++) {
    pinMode(ledPins[i], OUTPUT);
  }
}

void loop() {
  for (int i = 0; i < numLeds; i++) {
    digitalWrite(ledPins[i], HIGH);
    delay(200);
    digitalWrite(ledPins[i], LOW);
  }
}

Example 6.2: Temperature Alert System

const int tempPin = A0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  int temp = analogRead(tempPin);

  if (temp > 800) {
    Serial.println("High Temperature Alert!");
  } else if (temp > 600) {
    Serial.println("Moderate Temperature.");
  } else {
    Serial.println("Temperature is Normal.");
  }

  delay(1000);
}

7. Best Practices for Control Statements

1. Use Indentation:
   • Properly indent code for better readability.
2. Avoid Infinite Loops:
   • Ensure loop termination conditions are met.
3. Minimize Nested Loops:
   • Too many nested loops can make the program difficult to read and debug.
4. Use Switch for Multiple Conditions:
   • Use switch when handling multiple cases for a single variable.
5. Optimize Conditions:
   • Avoid redundant checks in conditional statements.

Conclusion

Control statements are fundamental for managing the flow of execution in Arduino programs. By using conditional and looping statements effectively, you can build powerful and dynamic Arduino applications.

This tutorial covered the essential control statements and provided examples to help you get started.

For more details, visit the official Arduino reference.