Timer interrupt for periodic tasks in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable the timer interrupt.

Embedded C

TIMSK |= (1 << [1]);

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ATOV1

BTOIE0

COCIE1A

DOCIE0

Attempts:

3 left

💡 Hint

Common Mistakes

Using the compare match interrupt bit instead of overflow interrupt bit.

Confusing timer numbers in bit names.

The TOIE0 bit enables the Timer0 overflow interrupt.

2fill in blank

medium

Complete the code to set the timer prescaler to 64.

Embedded C

TCCR0B = (1 << CS01) | [1];

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ACS10

BCS02

CCS00

DCS03

Attempts:

3 left

💡 Hint

Common Mistakes

Setting only one bit for prescaler 64.

Using bits for a different prescaler value.

Setting CS01 and CS00 bits sets the prescaler to 64 for Timer0.

3fill in blank

hard

Fix the error in the interrupt service routine declaration.

Embedded C

ISR([1]) {
    // Toggle LED
    PORTB ^= (1 << PORTB0);
}

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ATIMER0_OVF_vect

BTIMER1_COMPA_vect

CADC_vect

DUSART_RX_vect

Attempts:

3 left

💡 Hint

Common Mistakes

Using interrupt vectors for other peripherals.

Mixing Timer1 and Timer0 interrupt vectors.

The ISR must be declared for the Timer0 overflow vector TIMER0_OVF_vect to handle Timer0 interrupts.

4fill in blank

hard

Complete the ISR to count timer overflows and toggle LED every 100 overflows.

Embedded C

ISR(TIMER0_OVF_vect) {
    static uint8_t [1] = 0;
    [1]++;
    if([1] >= [2]) {
        PORTB ^= (1 << PORTB0);
        [1] = 0;
    }
}

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Acounter

B100

Cticks

D256

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting static (counter resets each ISR).

Using 256 (full overflow) instead of 100.

Not resetting the counter after task.

Use static counter to accumulate overflows. Toggle when counter >= 100 and reset to 0. This provides software division for longer periods.

5fill in blank

hard

Fill all three blanks for ~1s periodic task in ISR (16MHz, prescaler 64: overflow ~1.024ms, so ~976 for 1s).

Embedded C

ISR(TIMER0_OVF_vect) {
    static uint16_t [1] = 0;
    [1]++;
    if([1] >= [2]) {
        PORTB ^= (1 << PORTB0);
        [1] = [3];
    }
}

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Aoverflow_count

B976

Ctimer_count

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Wrong variable name or not uint16_t.

Incorrect count (e.g., 1000 or 1024).

Wrong reset value or comparison operator.

overflow_count (uint16_t) counts overflows. At >= 976 (~1s), toggle LED and reset to 0.