Button debouncing in software in Embedded C - Mini Project: Build & Apply

Button Debouncing in Software

📖 Scenario: You are working on a small embedded system with a push button connected to a microcontroller. When the button is pressed, the microcontroller reads the input pin. However, mechanical buttons often cause multiple rapid on/off signals called "bouncing" when pressed or released. This can cause the system to register multiple presses instead of one.To fix this, you will write a simple software debounce routine that waits for the button signal to stabilize before confirming a press.

🎯 Goal: Build a simple button debouncing program in C that reads a button input, waits for the signal to stabilize for a short time, and then confirms a single button press.

📋 What You'll Learn

Create a variable to simulate the button input state

Create a debounce delay constant

Write a function to check the button state with debouncing

Print the confirmed button press state

💡 Why This Matters

🌍 Real World

Button debouncing is essential in embedded systems to ensure reliable user input from mechanical buttons, avoiding multiple unwanted triggers.

💼 Career

Understanding button debouncing is important for embedded software developers working on hardware interfaces, IoT devices, and consumer electronics.

1

Create a variable to simulate the button input

Create an integer variable called button_state and set it to 1 to simulate the button being pressed (1 means pressed, 0 means not pressed).

Embedded C

# Create an integer variable called button_state and set it to 1
# Your code here

Need a hint?

Use int button_state = 1; to create the variable.

2

Create a debounce delay constant

Create a constant integer called DEBOUNCE_DELAY and set it to 50 to represent 50 milliseconds debounce delay.

Embedded C

int button_state = 1;
// Create a constant integer DEBOUNCE_DELAY set to 50
# Your code here

Need a hint?

Use const int DEBOUNCE_DELAY = 50; to create the delay constant.

3

Write a function to check the button state with debouncing

Write a function called debounce_button that takes no parameters and returns an integer. Inside the function, create a local variable stable_state and set it to the current button_state. Then simulate waiting for DEBOUNCE_DELAY milliseconds (you can just comment this as // wait DEBOUNCE_DELAY ms). Finally, return the stable_state.

Embedded C

int button_state = 1;
const int DEBOUNCE_DELAY = 50;

// Write the debounce_button function below
# Your code here

Need a hint?

Define the function with int debounce_button(). Use a local variable stable_state to hold button_state. Simulate delay with a comment.

4

Print the confirmed button press state

Call the debounce_button() function and store its return value in an integer variable called confirmed_state. Then print the text "Button state after debounce: " followed by the value of confirmed_state using printf.

Embedded C

int button_state = 1;
const int DEBOUNCE_DELAY = 50;

int debounce_button() {
    int stable_state = button_state;
    // wait DEBOUNCE_DELAY ms
    return stable_state;
}

// Call debounce_button and print the result
# Your code here

Need a hint?

Use int confirmed_state = debounce_button(); and printf("Button state after debounce: %d\n", confirmed_state);.