xEventGroupCreate() function in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an event group using FreeRTOS.

FreeRTOS

EventGroupHandle_t xEventGroup = [1]();

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

AvTaskDelay

BxQueueCreate

CxEventGroupCreate

DxSemaphoreCreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using queue or semaphore creation functions instead of event group creation.

Forgetting to assign the returned handle.

The function xEventGroupCreate() is used to create a new event group in FreeRTOS.

2fill in blank

medium

Complete the code to check if the event group was created successfully.

FreeRTOS

if (xEventGroup == [1]) {
    // Handle error
}

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

ANULL

B0

C1

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Checking against 0 or false instead of NULL.

Not checking the return value at all.

The function xEventGroupCreate() returns NULL if the event group creation fails.

3fill in blank

hard

Fix the error in the code to correctly create an event group.

FreeRTOS

EventGroupHandle_t xEventGroup;
xEventGroup = [1]();

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

AxEventGroupCreateMutex

BxEventGroupCreate

CxSemaphoreCreateBinary

DvEventGroupCreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using semaphore or mutex creation functions instead of event group creation.

Using a void function instead of one that returns a handle.

The correct function to create an event group is xEventGroupCreate(). Other options are incorrect or do not exist.

4fill in blank

hard

Fill both blanks to create an event group and check if creation was successful.

FreeRTOS

EventGroupHandle_t xEventGroup = [1]();
if (xEventGroup == [2]) {
    // Error handling
}

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

AxEventGroupCreate

BNULL

C0

DxSemaphoreCreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect functions for creation.

Checking against 0 instead of NULL.

First, create the event group with xEventGroupCreate(). Then check if the returned handle is NULL to detect failure.

5fill in blank

hard

Fill all three blanks to create an event group, check for success, and set bits.

FreeRTOS

EventGroupHandle_t xEventGroup = [1]();
if (xEventGroup != [2]) {
    [3](xEventGroup, BIT_0);
}

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

AxEventGroupCreate

BNULL

CxEventGroupSetBits

DvTaskDelay

Attempts:

3 left

💡 Hint

Common Mistakes

Using delay functions instead of bit setting.

Not checking for NULL before setting bits.

Create the event group with xEventGroupCreate(). Check that the handle is not NULL. Then set bits using xEventGroupSetBits().

Practice

1. What does the xEventGroupCreate() function do in FreeRTOS?

easy

A. Creates a new event group and returns its handle

B. Deletes an existing event group

C. Sends an event to a task

D. Creates a new task

Solution

1. Step 1: Understand the purpose of xEventGroupCreate()

   This function is designed to create a new event group in FreeRTOS, which is used for task communication.

2. Step 2: Identify the return value

   The function returns a handle to the newly created event group, which is used to interact with it later.

3. Final Answer:

   Creates a new event group and returns its handle -> Option A

4. Quick Check:

   xEventGroupCreate() creates event group = A [OK]

Hint: Remember: create means new event group and get handle [OK]

Common Mistakes:

• Confusing creation with deletion
• Thinking it sends events instead of creating groups
• Assuming it creates tasks

2. Which of the following is the correct way to declare and create an event group using xEventGroupCreate()?

easy

A. xEventGroupHandle_t xEventGroup = xEventGroupCreate();

B. EventGroupHandle_t xEventGroup = CreateEventGroup();

C. EventGroupHandle_t xEventGroup = xCreateEventGroup();

D. EventGroupHandle_t xEventGroup = xEventGroupCreate();

Solution

1. Step 1: Check the correct type name

   The correct type for event group handles is EventGroupHandle_t.

2. Step 2: Verify the function name

   The function to create an event group is exactly xEventGroupCreate().

3. Final Answer:

   EventGroupHandle_t xEventGroup = xEventGroupCreate(); -> Option D

4. Quick Check:

   Correct type and function name = C [OK]

Hint: Match exact type and function name spelling [OK]

Common Mistakes:

• Using wrong type name like xEventGroupHandle_t
• Using incorrect function names
• Missing the semicolon

3. What will be the output of the following code snippet?

EventGroupHandle_t xGroup;
xGroup = xEventGroupCreate();
if (xGroup == NULL) {
    printf("Failed to create event group\n");
} else {
    printf("Event group created successfully\n");
}

medium

A. Event group created successfully

B. No output

C. Compilation error

D. Failed to create event group

Solution

1. Step 1: Understand xEventGroupCreate() return value

   This function returns a valid handle if creation succeeds, otherwise NULL.

2. Step 2: Analyze the if condition

   The code checks if the handle is NULL. If not NULL, it prints success message.

3. Final Answer:

   Event group created successfully -> Option A

4. Quick Check:

   Handle != NULL means success = D [OK]

Hint: Check if handle is NULL to confirm creation success [OK]

Common Mistakes:

• Assuming NULL means success
• Confusing printf output strings
• Ignoring the if condition logic

4. Identify the error in the following code snippet that uses xEventGroupCreate():

EventGroupHandle_t xGroup;
xGroup = xEventGroupCreate;
if (xGroup == NULL) {
    // handle error
}

medium

A. Incorrect variable type for xGroup

B. Missing parentheses when calling xEventGroupCreate

C. No check for NULL handle

D. Using wrong function name

Solution

1. Step 1: Check function call syntax

   The code assigns xEventGroupCreate without parentheses, so it assigns the function pointer, not the result.

2. Step 2: Understand correct usage

   To call the function and get the handle, parentheses are required: xEventGroupCreate().

3. Final Answer:

   Missing parentheses when calling xEventGroupCreate -> Option B

4. Quick Check:

   Function call needs () = B [OK]

Hint: Always use () to call functions, not just name [OK]

Common Mistakes:

• Forgetting parentheses on function calls
• Confusing function pointer with return value
• Not checking for NULL after creation

5. You want to create an event group and ensure your program handles failure gracefully. Which code snippet correctly creates the event group and checks for failure?

hard

A. EventGroupHandle_t xGroup = xEventGroupCreate(); if (xGroup == NULL) { /* proceed */ } else { /* handle error */ }

B. EventGroupHandle_t xGroup; xGroup = xEventGroupCreate; if (xGroup == NULL) { /* handle error */ }

C. EventGroupHandle_t xGroup = xEventGroupCreate(); if (xGroup != NULL) { /* proceed */ } else { /* handle error */ }

D. EventGroupHandle_t xGroup = CreateEventGroup(); if (xGroup == NULL) { /* handle error */ }

Solution

1. Step 1: Verify correct function call and assignment

   EventGroupHandle_t xGroup = xEventGroupCreate(); if (xGroup != NULL) { /* proceed */ } else { /* handle error */ } correctly calls xEventGroupCreate() with parentheses and assigns the handle.

2. Step 2: Check the logic for failure handling

   It checks if the handle is not NULL to proceed, else handles error. This is the correct logic.

3. Final Answer:

   EventGroupHandle_t xGroup = xEventGroupCreate(); if (xGroup != NULL) { /* proceed */ } else { /* handle error */ } -> Option C

4. Quick Check:

   Correct call and NULL check = A [OK]

Hint: Call with () and check if handle is NULL to handle errors [OK]

Common Mistakes:

• Not using parentheses on function call
• Reversing NULL check logic
• Using wrong function name