Task 1: A Modular Calculator with Arduino

4. Lab Procedure

Follow these steps carefully to build your project.

Part A: Project Setup - Creating the Files

In the Arduino IDE, a project (or "sketch") can be composed of multiple files, which appear as tabs. We will create three files for our project.

1. Open the Arduino IDE and save the new, empty sketch. Name it Lab1_Calculator. This creates a file named Lab1_Calculator.ino.
2. Create the header file. Click the downward arrow on the right side of the tab bar and select "New Tab".
3. Name the new file calculator.h and click OK.
4. Create the source file. Repeat the process: click the "New Tab" button, name the new file calculator.cpp, and click OK.

You should now have three tabs in your IDE: Lab1_Calculator.ino, calculator.h, and calculator.cpp.

Part B: The Header File (calculator.h)

The header file declares the functions that our calculator module will provide. It acts like a public menu of our module's capabilities.

Copy the following code into your calculator.h file.

// This is the start of a "header guard". It prevents the file from being included more than once,
// which can cause compilation errors. The name CALCULATOR_H should be unique to this project.
#ifndef CALCULATOR_H
#define CALCULATOR_H

// Function Declarations (Prototypes)
// These tell the compiler that these functions exist, what parameters they take,
// and what type of value they return. The actual code is in calculator.cpp.

// Function to add two numbers
float add(float a, float b);

// Function to subtract two numbers
float subtract(float a, float b);

// Function to multiply two numbers
float multiply(float a, float b);

// Function to divide two numbers
float divide(float a, float b);


#endif // This ends the header guard.

Part C: The Implementation File (calculator.cpp)

This is where we write the actual logic for the functions we declared in the header file.

Copy the following code into your calculator.cpp file. Your task is to complete the logic inside each function.

// We must include Arduino.h to use standard Arduino types and functions.
#include 

// We include our own header file to link the declarations to these definitions.
#include "calculator.h"

// Function Definitions

float add(float a, float b) {
  // TODO: Return the sum of a and b.
  return a + b;
}

float subtract(float a, float b) {
  // TODO: Return the result of a minus b.
  return a - b;
}

float multiply(float a, float b) {
  // TODO: Return the product of a and b.
  return a * b;
}

float divide(float a, float b) {
  // We must handle division by zero, as it's an invalid operation.
  if (b == 0) {
    Serial.println("Error: Division by zero!");
    return 0; // Return 0 or another indicator of an error.
  } else {
    // TODO: Return the result of a divided by b.
    return a / b;
  }
}

Part D: The Main Sketch (Lab1_Calculator.ino)

This is the main entry point of our program. It will handle user interaction through the Serial Monitor and call the functions from our calculator module.

Copy the following code into your Lab1_Calculator.ino file.

// Include our custom calculator header file.
// Use "" for local project files and <> for system/library files.
#include "calculator.h"

void setup() {
  // Initialize serial communication at 9600 bits per second.
  Serial.begin(9600);
  
  // Wait for the serial port to connect. Needed for native USB port only.
  while (!Serial); 
  
  Serial.println("Arduino Calculator is ready!");
  Serial.println("Enter a calculation in the format: number operator number");
  Serial.println("For example: 10.5 + 5");
  Serial.println("------------------------------------");
}

void loop() {
  // Check if there is data available to read from the serial port.
  if (Serial.available() > 0) {
    
    // 1. Read the first number.
    // parseFloat() reads digits until it finds a non-digit character.
    float num1 = Serial.parseFloat();

    // 2. Read the operator.
    // We need to skip any whitespace between the number and the operator.
    char op = ' ';
    while (Serial.available() > 0) {
      char c = Serial.read();
      if (c == '+' || c == '-' || c == '*' || c == '/') {
        op = c;
        break; // Found the operator, exit the loop.
      }
    }
    
    // 3. Read the second number.
    float num2 = Serial.parseFloat();

    float result = 0;
    bool validOperation = true;

    // 4. Use a switch statement to perform the correct operation.
    switch (op) {
      case '+':
        result = add(num1, num2);
        break;
      case '-':
        result = subtract(num1, num2);
        break;
      case '*':
        result = multiply(num1, num2);
        break;
      case '/':
        result = divide(num1, num2);
        break;
      default:
        Serial.println("Invalid operator. Please use +, -, *, or /");
        validOperation = false;
        break;
    }

    // 5. Print the result if the operation was valid.
    if (validOperation) {
      Serial.print("Result: ");
      Serial.print(num1);
      Serial.print(" ");
      Serial.print(op);
      Serial.print(" ");
      Serial.print(num2);
      Serial.print(" = ");
      Serial.println(result);
    }
    
    Serial.println("------------------------------------");
    
    // Clear any remaining characters from the input buffer
    while(Serial.available() > 0) {
      Serial.read();
    }
  }
}

Part E: Testing Your Calculator

1. Verify and upload the sketch to your Arduino Uno.
2. Open the Serial Monitor (Tools -> Serial Monitor or Ctrl+Shift+M).
3. Make sure the baud rate is set to 9600 baud in the bottom-right corner of the Serial Monitor.
4. In the input box at the top, type a calculation like 15 + 30 and press Enter.
5. The Arduino should print the result.
6. Test all four operations (+, -, *, /). Be sure to test the division by zero case (e.g., 100 / 0).

Your Serial Monitor output should look something like this:

Arduino Calculator is ready!
Enter a calculation in the format: number operator number
For example: 10.5 + 5
------------------------------------
Result: 15.00 + 30.00 = 45.00
------------------------------------
Result: 100.00 / 4.00 = 25.00
------------------------------------
Error: Division by zero!
Result: 100.00 / 0.00 = 0.00
------------------------------------