Loops (for, while)

Okay, here's an explanation of for and while loops in Arduino, with examples, strictly in English and without any external links or images.

Loops in Arduino: Controlling Repeated Actions

Loops are fundamental programming structures that allow you to repeat a block of code multiple times. This is incredibly useful for tasks like reading sensor data repeatedly, controlling the blinking of an LED, or performing calculations on a series of values. Arduino supports two main types of loops: for and while.

1. for Loop

The for loop is best when you know in advance how many times you want to repeat the code. It combines initialization, condition checking, and increment/decrement all in one line.

• Syntax:

  for (initialization; condition; increment/decrement) {
    // Code to be repeated
  }
  

• Explanation:

  • Initialization: This part is executed once at the beginning of the loop. It's typically used to declare and initialize a counter variable (e.g., int i = 0;).
  • Condition: This is a Boolean expression (true/false). The code inside the loop will only execute if the condition is true. The condition is checked before each iteration of the loop.
  • Increment/Decrement: This part is executed after each iteration of the loop. It's commonly used to increase or decrease the counter variable (e.g., i++ or i--).

• Example: Blinking an LED 5 times.

  int ledPin = 13;  // LED connected to digital pin 13
  
  void setup() {
    pinMode(ledPin, OUTPUT); // Sets the digital pin as output
  }
  
  void loop() {
    for (int i = 0; i < 5; i++) { // Initialize i to 0, loop as long as i < 5, increment i after each loop
      digitalWrite(ledPin, HIGH); // Turn the LED on
      delay(500);              // Wait for 0.5 seconds
      digitalWrite(ledPin, LOW);  // Turn the LED off
      delay(500);              // Wait for 0.5 seconds
    }
    delay(3000); // Wait 3 seconds before repeating the blinking sequence
  }
  

  In this example:

  • int i = 0; initializes a counter variable i to 0.
  • i < 5; is the condition. The loop continues as long as i is less than 5.
  • i++; increments i by 1 after each time the code inside the curly braces is executed.
  • The LED will blink on and off 5 times, then the program will wait 3 seconds.

2. while Loop

The while loop is best when you want to repeat code as long as a certain condition is true, but you might not know in advance how many times it will repeat.

• Syntax:

  while (condition) {
    // Code to be repeated
  }
  

• Explanation:

  • Condition: This is a Boolean expression (true/false). The code inside the loop will only execute if the condition is true. The condition is checked before each iteration of the loop. Crucially, something inside the loop must eventually make the condition false, or you'll end up with an infinite loop.

• Example: Reading a sensor until it reaches a certain value. (Simulated here since I can't interact with a real sensor).

  int sensorPin = A0; // Analog pin A0 for the sensor (hypothetical)
  int sensorValue = 0;
  
  void setup() {
    Serial.begin(9600);  // Initialize serial communication
  }
  
  void loop() {
    //Simulate sensor reading
    static int simulatedValue = 0;
    sensorValue = simulatedValue;
    simulatedValue = simulatedValue + 10;
  
    while (sensorValue < 500) {
      Serial.print("Sensor value: ");
      Serial.println(sensorValue);
      delay(100);
      //Simulate sensor reading again within the loop
      sensorValue = simulatedValue;
      simulatedValue = simulatedValue + 10;
  
    }
    Serial.println("Sensor value is 500 or more.  Exiting loop.");
    delay(3000); //Wait before reseting the simulation.
    simulatedValue = 0;
  }
  

  In this example:

  • The while (sensorValue < 500) condition checks if the sensorValue is less than 500.
  • The code inside the while loop will continue to execute as long as sensorValue is less than 500. Inside the loop, the sensor value is printed to the serial monitor and simuated to increase. Once sensorValue reaches 500 or more, the condition becomes false, and the loop stops. It then restarts after 3 seconds.

Key Differences Summary

• for loop: Use when you know the number of iterations in advance. Initialization, condition, and increment are all in one place.
• while loop: Use when you want to repeat code as long as a condition is true, and you might not know the number of iterations beforehand. You are responsible for making sure the condition eventually becomes false.

In both cases, be very careful to avoid infinite loops (where the condition is always true), as this can cause your Arduino program to freeze.