Hard real-time vs soft real-time in FreeRTOS - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a task that must meet a strict deadline (hard real-time).

FreeRTOS

xTaskCreate(taskFunction, "Task1", configMINIMAL_STACK_SIZE, NULL, [1], NULL);

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AconfigMAX_PRIORITIES - 1

BtskIDLE_PRIORITY

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using low priority for hard real-time tasks.

Confusing priority values.

Hard real-time tasks require the highest priority to meet strict deadlines, so we use configMAX_PRIORITIES - 1.

2fill in blank

medium

Complete the code to delay a soft real-time task without blocking other tasks.

FreeRTOS

vTaskDelay([1]);

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A0

BpdMS_TO_TICKS(100)

C100

DportMAX_DELAY

Attempts:

3 left

💡 Hint

Common Mistakes

Passing raw milliseconds instead of ticks.

Using portMAX_DELAY which blocks indefinitely.

Use pdMS_TO_TICKS(100) to convert milliseconds to ticks for a non-blocking delay.

3fill in blank

hard

Fix the error in the code to ensure a hard real-time task does not miss its deadline.

FreeRTOS

if (xTaskGetTickCount() > [1]) {
    // handle deadline miss
}

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AxTaskGetTickCount()

BportMAX_DELAY

CpdMS_TO_TICKS(1000)

Ddeadline

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing to portMAX_DELAY which is a constant for max delay.

Comparing to current tick count which is always true.

The code should compare the current tick count to a predefined deadline to detect deadline misses.

4fill in blank

hard

Fill both blanks to create a soft real-time task that waits for a notification with a timeout.

FreeRTOS

if (xTaskNotifyWait(0, 0, NULL, [1]) == [2]) {
    // notification received
}

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ApdMS_TO_TICKS(5000)

BpdPASS

CportMAX_DELAY

DpdFAIL

Attempts:

3 left

💡 Hint

Common Mistakes

Using portMAX_DELAY which waits indefinitely.

Checking for pdFAIL instead of pdPASS.

The task waits up to 5000 ms (pdMS_TO_TICKS(5000)) and checks if the notification was successful (pdPASS).

5fill in blank

hard

Fill all three blanks to define a hard real-time task that suspends itself and resumes after an interrupt.

FreeRTOS

void [1](void *pvParameters) {
    for (;;) {
        vTaskSuspend(NULL);
        // task resumed by [2]
        [3]();
    }
}

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AHardRealTimeTask

Ban ISR

CprocessCriticalData

DSoftRealTimeTask

Attempts:

3 left

💡 Hint

Common Mistakes

Using a soft real-time task name for a hard real-time task.

Not calling the processing function after resume.

The task named HardRealTimeTask suspends itself and is resumed by an interrupt service routine (an ISR), then calls processCriticalData().