Debouncing as a state machine in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the initial state of the debounce state machine.

Embedded C

typedef enum { BUTTON_[1], BUTTON_PRESSED, BUTTON_RELEASED } ButtonState;

Drag options to blanks, or click blank then click option'

AIDLE

BPRESSED

CRELEASED

DWAIT

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a state that implies the button is already pressed.

Using a state name not defined in the enum.

The initial state is usually IDLE, meaning no button press detected yet.

2fill in blank

medium

Complete the code to check if the button input is pressed (active low).

Embedded C

if (button_input == [1]) {

Drag options to blanks, or click blank then click option'

A0

B1

CHIGH

DTRUE

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 for pressed state.

Confusing HIGH and LOW logic levels.

For active low buttons, pressed means the input reads 0.

3fill in blank

hard

Fix the error in the debounce timer reset code.

Embedded C

debounce_timer = [1];

Drag options to blanks, or click blank then click option'

A0

BDEBOUNCE_DELAY

C1

D-1

Attempts:

3 left

💡 Hint

Common Mistakes

Setting timer to 0 resets it immediately.

Using negative values causes errors.

The timer should be set to the debounce delay constant to start counting down.

4fill in blank

hard

Fill both blanks to update the state machine when the button is pressed and debounce timer expires.

Embedded C

if (debounce_timer == 0 && button_state == [1]) {
    button_state = [2];
}

Drag options to blanks, or click blank then click option'

ABUTTON_IDLE

BBUTTON_PRESSED

CBUTTON_RELEASED

DBUTTON_WAIT

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong current state in condition.

Setting state to RELEASED instead of PRESSED.

When timer expires and state is IDLE, update state to PRESSED.

5fill in blank

hard

Fill all three blanks to implement the debounce state machine update logic.

Embedded C

switch (button_state) {
    case BUTTON_IDLE:
        if (button_input == [1]) {
            debounce_timer = [2];
            button_state = [3];
        }
        break;
    // other states omitted for brevity
}

Drag options to blanks, or click blank then click option'

A0

BDEBOUNCE_DELAY

CBUTTON_WAIT

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 0 for pressed input.

Setting wrong state after starting timer.

When button input is 0 (pressed), start debounce timer and move to WAIT state.