Watchdog task pattern in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a watchdog timer with FreeRTOS API.

FreeRTOS

TimerHandle_t watchdogTimer = xTimerCreate("Watchdog", pdMS_TO_TICKS([1]), pdFALSE, NULL, watchdogCallback);

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A2000

B10000

C1000

D5000

Attempts:

3 left

💡 Hint

Common Mistakes

Setting the timeout too short causing false triggers.

Using zero or negative values which are invalid.

The watchdog timer is set to 5000 milliseconds (5 seconds) to monitor task health.

2fill in blank

medium

Complete the code to start the watchdog timer after creation.

FreeRTOS

if (xTimerStart(watchdogTimer, [1]) != pdPASS) {
    // Handle error
}

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A0

BportMAX_DELAY

C100

DpdMS_TO_TICKS(1000)

Attempts:

3 left

💡 Hint

Common Mistakes

Using a blocking delay unnecessarily.

Passing an invalid block time causing errors.

Passing 0 as block time means the call will not block if the timer command queue is full.

3fill in blank

hard

Fix the error in the watchdog task function to reset the timer correctly.

FreeRTOS

void WatchdogTask(void *pvParameters) {
    for (;;) {
        if (xTimerReset(watchdogTimer, [1]) != pdPASS) {
            // Handle reset failure
        }
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

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A0

BportMAX_DELAY

CpdMS_TO_TICKS(1000)

D1000

Attempts:

3 left

💡 Hint

Common Mistakes

Using a blocking delay causing watchdog to miss resets.

Passing incorrect block time values.

Using 0 as block time ensures the reset command is sent without blocking.

4fill in blank

hard

Fill both blanks to create a dictionary of task names and their last heartbeat times.

FreeRTOS

typedef struct {
    char name[16];
    TickType_t lastHeartbeat;
} TaskStatus;

TaskStatus taskStatusArray[[1]];

void updateHeartbeat(const char* taskName, TickType_t tick) {
    for (int i = 0; i < [2]; i++) {
        if (strcmp(taskStatusArray[i].name, taskName) == 0) {
            taskStatusArray[i].lastHeartbeat = tick;
            break;
        }
    }
}

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A5

B10

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching array size and loop limit causing out-of-bounds errors.

Using too small array size for the number of tasks.

The array size and loop limit must match the number of tasks monitored, here 10.

5fill in blank

hard

Fill all three blanks to implement the watchdog check function that resets system on timeout.

FreeRTOS

void checkWatchdog() {
    TickType_t currentTick = xTaskGetTickCount();
    for (int i = 0; i < [1]; i++) {
        if (currentTick - taskStatusArray[i].lastHeartbeat > [2]) {
            [3]();
        }
    }
}

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A5

BpdMS_TO_TICKS(5000)

CsystemReset

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong timeout values causing premature resets.

Calling wrong function or missing reset call.

The function loops over 10 tasks, checks if heartbeat is older than 5 seconds, and calls systemReset if so.