Task function signature in FreeRTOS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the correct signature of a FreeRTOS task function?

A FreeRTOS task function must return void and take a single void pointer parameter. Example:

void TaskName(void *pvParameters)

beginner

Why does a FreeRTOS task function take a void pointer as a parameter?

The void pointer allows passing any type of data to the task when it starts, making the task flexible to receive different inputs.

beginner

Can a FreeRTOS task function return a value?

No, a FreeRTOS task function must have a void return type because tasks run indefinitely or until deleted, and the scheduler does not expect a return value.

intermediate

What happens if a FreeRTOS task function does not include an infinite loop?

If the task function returns (exits), the task is deleted automatically by the scheduler, which can cause unexpected behavior if not intended.

beginner

Show an example of a minimal FreeRTOS task function signature and body.

void MyTask(void *pvParameters) {
    for (;;) {
        // Task code here
    }
}

What is the return type of a FreeRTOS task function?

A void

B int

C bool

D char*

FreeRTOS task functions must return void because the scheduler does not expect any return value.

What parameter type does a FreeRTOS task function accept?

A char

B int

C void*

D float

The task function accepts a void pointer to allow passing any type of data.

What happens if a FreeRTOS task function returns instead of looping forever?

A The system crashes

B The task restarts automatically

C Nothing happens

D The task is deleted

If the task function returns, the task is deleted by the scheduler.

Which of these is a correct FreeRTOS task function signature?

A int Task(void)

B void Task(void *pvParameters)

C void Task()

D int Task(void *pvParameters)

The correct signature is void return type with a void pointer parameter.

Why is the parameter of a FreeRTOS task function a void pointer?

A To allow passing any type of data

B To restrict data types

C Because tasks cannot have parameters

D To return data from the task

A void pointer allows passing any type of data to the task.

Describe the required signature of a FreeRTOS task function and explain why it is designed that way.

Think about how tasks receive data and how the scheduler manages them.

Explain what happens if a FreeRTOS task function finishes execution and returns instead of looping forever.

Consider the lifecycle of a task in FreeRTOS.

Practice

1.

What is the correct signature for a FreeRTOS task function?

easy

A. int TaskName(int param)

B. void TaskName(void *pvParameters)

C. void TaskName()

D. void TaskName(int *param)

Solution

1. Step 1: Recall FreeRTOS task function signature

   FreeRTOS tasks must have the signature with return type void and a single void pointer parameter.

2. Step 2: Match the signature with options

   Only void TaskName(void *pvParameters) matches void TaskName(void *pvParameters) exactly.

3. Final Answer:

   void TaskName(void *pvParameters) -> Option B

4. Quick Check:

   Task signature = void TaskName(void *pvParameters) [OK]

Hint: Task functions always return void and take void* parameter [OK]

Common Mistakes:

• Using int return type instead of void
• Omitting the void* parameter
• Using incorrect parameter types

2.

Which of the following is a syntactically correct FreeRTOS task function declaration?

void MyTask(_____)

easy

A. void *pvParameters

B. int param

C. char *name

D. void

Solution

1. Step 1: Understand parameter type for FreeRTOS tasks

   Task functions must accept a single parameter of type void *.

2. Step 2: Check each option

   Only void *pvParameters uses void *pvParameters, which is correct syntax.

3. Final Answer:

   void *pvParameters -> Option A

4. Quick Check:

   Parameter type = void *pvParameters [OK]

Hint: Task parameter must be void pointer (void*) [OK]

Common Mistakes:

• Using int or char pointer instead of void pointer
• Using void without pointer
• Missing parameter entirely

3.

What will happen if you run this FreeRTOS task function?

void ExampleTask(void *pvParameters) {
    for(;;) {
        // Task code here
    }
}

medium

A. The task will return a value causing runtime error.

B. The task will run once and then exit.

C. The task will cause a compile error.

D. The task will run repeatedly in an infinite loop.

Solution

1. Step 1: Analyze the task function loop

   The task contains a for(;;) infinite loop, so it runs repeatedly.

2. Step 2: Understand FreeRTOS task behavior

   Tasks should not return; they run inside infinite loops to keep running.

3. Final Answer:

   The task will run repeatedly in an infinite loop. -> Option D

4. Quick Check:

   Infinite loop in task = runs repeatedly [OK]

Hint: FreeRTOS tasks run inside infinite loops [OK]

Common Mistakes:

• Thinking task runs once and exits
• Expecting return value from task
• Confusing infinite loop with error

4.

Identify the error in this FreeRTOS task function:

void FaultyTask(void *pvParameters) {
    int count = 0;
    while(count < 5) {
        count++;
    }
    return;
}

medium

A. The function should not return; it must loop forever.

B. The parameter type is incorrect.

C. The variable count should be a pointer.

D. The while loop condition is invalid syntax.

Solution

1. Step 1: Check task function return behavior

   FreeRTOS tasks must not return; they should run inside infinite loops.

2. Step 2: Analyze the code flow

   This task loops 5 times then returns, which is incorrect for FreeRTOS tasks.

3. Final Answer:

   The function should not return; it must loop forever. -> Option A

4. Quick Check:

   Tasks must not return, use infinite loop [OK]

Hint: Tasks must never return; use infinite loops [OK]

Common Mistakes:

• Allowing task to return
• Changing parameter type incorrectly
• Misunderstanding loop conditions

5.

You want to pass an integer value to a FreeRTOS task. Which is the correct way to define and use the task function?

void NumberTask(_____)
{
    int received = *(int *)pvParameters;
    for(;;) {
        // Use received value
    }
}

hard

A. void pvParameters

B. int pvParameters

C. void *pvParameters

D. int *pvParameters

Solution

1. Step 1: Recall task function parameter type

   Task functions must accept a void * parameter to allow any data type.

2. Step 2: Understand data passing

   The integer is passed via pointer cast from void *, so parameter must be void *pvParameters.

3. Final Answer:

   void *pvParameters -> Option C

4. Quick Check:

   Use void* parameter to pass any data type [OK]

Hint: Always use void* parameter to pass data to tasks [OK]

Common Mistakes:

• Using int instead of void* parameter
• Using void without pointer
• Not casting void* to correct type inside task