Why interrupt handling is critical in RTOS in FreeRTOS - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an interrupt service routine (ISR) in FreeRTOS.

FreeRTOS

void vExampleISR(void) {
    BaseType_t xHigherPriorityTaskWoken = [1];
    // ISR code here
}

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ApdFALSE

BpdTRUE

CpdPASS

DpdFAIL

Attempts:

3 left

💡 Hint

Common Mistakes

Using pdTRUE instead of pdFALSE to initialize xHigherPriorityTaskWoken.

In FreeRTOS, pdFALSE is used to initialize xHigherPriorityTaskWoken to indicate no higher priority task was woken yet.

2fill in blank

medium

Complete the code to notify a task from an ISR in FreeRTOS.

FreeRTOS

void vExampleISR(void) {
    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    vTaskNotifyGiveFromISR(taskHandle, [1]);
    portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

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ANULL

BpdFALSE

CxHigherPriorityTaskWoken

D&xHigherPriorityTaskWoken

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the variable directly instead of its address.

Passing NULL which disables task wake notification.

The function vTaskNotifyGiveFromISR requires a pointer to xHigherPriorityTaskWoken to update it if a higher priority task was woken.

3fill in blank

hard

Fix the error in the ISR code to correctly clear the interrupt flag.

FreeRTOS

void vExampleISR(void) {
    BaseType_t xHigherPriorityTaskWoken = pdFALSE;
    // Clear interrupt flag
    [1];
    vTaskNotifyGiveFromISR(taskHandle, &xHigherPriorityTaskWoken);
    portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

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ACLEAR_INTERRUPT_FLAG()

Bclear_interrupt_flag()

CClearInterruptFlag()

DclearInterruptFlag()

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or camelCase function names that do not exist.

Interrupt flags are usually cleared by a macro or function named in uppercase like CLEAR_INTERRUPT_FLAG() to ensure the hardware interrupt is acknowledged properly.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps interrupt names to their priority levels, only including priorities higher than 3.

FreeRTOS

interrupt_priorities = {name: level for name, level in interrupts.items() if level [1] [2]

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A>

B3

C<

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causing wrong filtering.

Using wrong threshold values.

The comprehension filters interrupts with priority levels greater than 3 using level > 3.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps task names in uppercase to their stack sizes, only for tasks with stack size greater than 1000.

FreeRTOS

task_stacks = [1]: [2] for [3], [2] in tasks.items() if [2] > 1000

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Aname.upper()

Bstack_size

Cname

Dtask

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names or forgetting to convert names to uppercase.

The comprehension uses name as the loop variable, maps name.upper() to stack_size, and filters stack sizes greater than 1000.