Why tasks are the building blocks in FreeRTOS - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a FreeRTOS task that runs the function TaskFunction.

FreeRTOS

xTaskCreate([1], "Task1", 1000, NULL, 1, NULL);

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

AvTaskStartScheduler

BTaskFunction

CxQueueCreate

DvTaskDelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using scheduler or queue functions instead of the task function name.

Passing NULL instead of the task function.

The xTaskCreate function needs the task function name as its first argument to create a task.

2fill in blank

medium

Complete the code to start the FreeRTOS scheduler after creating tasks.

FreeRTOS

[1]();

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

AvTaskStartScheduler

BxTaskCreate

CvTaskDelay

DxQueueSend

Attempts:

3 left

💡 Hint

Common Mistakes

Calling task creation functions instead of starting the scheduler.

Using delay or queue functions here.

The vTaskStartScheduler function starts the FreeRTOS scheduler, which begins running tasks.

3fill in blank

hard

Fix the error in the task function prototype to match FreeRTOS requirements.

FreeRTOS

void [1](void *pvParameters) { /* task code */ }

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

ATaskFunction

BTaskFunction(void)

CTaskFunction(int param)

DTaskFunction()

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the parameter or using wrong parameter types.

Using empty parentheses which is invalid in C for this case.

FreeRTOS task functions must have the prototype void TaskName(void *pvParameters).

4fill in blank

hard

Fill both blanks to create a task that runs Task1Function with priority 2.

FreeRTOS

xTaskCreate([1], "Task1", 1000, NULL, [2], NULL);

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

ATask1Function

B1

C2

DvTaskStartScheduler

Attempts:

3 left

💡 Hint

Common Mistakes

Using the scheduler function as a task function.

Setting priority to 1 instead of 2.

The first blank is the task function name. The second blank is the priority number, here 2.

5fill in blank

hard

Fill both blanks to create a dictionary of task names and their priorities for tasks with priority greater than 1.

FreeRTOS

task_priorities = { [2]: [1] for [3] in tasks if tasks[[3]] > 1}

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

A{

Btasks[task]

Ctask

D}

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the curly braces.

Using wrong variable names or missing the condition.

This is a dictionary comprehension. { starts it, task is the key, and tasks[task] is the value.

Practice

1. Why are tasks considered the building blocks in FreeRTOS?

easy

A. Because tasks store data permanently in memory.

B. Because tasks allow the program to run multiple jobs independently and smoothly.

C. Because tasks handle hardware interrupts directly.

D. Because tasks compile the program faster.

Solution

1. Step 1: Understand the role of tasks in FreeRTOS

   Tasks divide a program into small, independent jobs that can run at the same time.

2. Step 2: Recognize the benefit of tasks

   This division helps the device perform many things smoothly without waiting for one job to finish.

3. Final Answer:

   Because tasks allow the program to run multiple jobs independently and smoothly. -> Option B

4. Quick Check:

   Tasks = Independent jobs running smoothly [OK]

Hint: Tasks run jobs independently for smooth multitasking [OK]

Common Mistakes:

• Thinking tasks store data permanently
• Confusing tasks with interrupt handlers
• Believing tasks speed up compilation

2. Which of the following is the correct way to create a task in FreeRTOS?

easy

A. xTaskCreate(TaskFunction, "TaskName", StackSize, NULL, Priority, &TaskHandle);

B. CreateTask(TaskFunction, Priority, StackSize);

C. task_create(TaskFunction, StackSize, Priority);

D. StartTask(TaskFunction, "TaskName", Priority);

Solution

1. Step 1: Recall the FreeRTOS task creation function

   The correct function to create a task is xTaskCreate with parameters: function, name, stack size, parameters, priority, and handle.

2. Step 2: Compare options with correct syntax

   Only xTaskCreate(TaskFunction, "TaskName", StackSize, NULL, Priority, &TaskHandle); matches the exact syntax and parameter order of xTaskCreate.

3. Final Answer:

   xTaskCreate(TaskFunction, "TaskName", StackSize, NULL, Priority, &TaskHandle); -> Option A

4. Quick Check:

   Correct function and parameters = xTaskCreate(TaskFunction, "TaskName", StackSize, NULL, Priority, &TaskHandle); [OK]

Hint: Remember xTaskCreate with 6 parameters for tasks [OK]

Common Mistakes:

• Using wrong function names like CreateTask
• Mixing parameter order
• Omitting task handle parameter

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

void Task1(void *pvParameters) {
  for (;;) {
    printf("Task1 running\n");
    vTaskDelay(pdMS_TO_TICKS(1000));
  }
}

void Task2(void *pvParameters) {
  for (;;) {
    printf("Task2 running\n");
    vTaskDelay(pdMS_TO_TICKS(500));
  }
}

medium

A. Only Task1 will print because Task2 is blocked.

B. Both tasks print at the same time without delay.

C. Task2 will print once, then stop.

D. Task1 running every 1 second, Task2 running every 0.5 seconds, both printing alternately.

Solution

1. Step 1: Analyze the delay times in each task

   Task1 delays 1000 ms (1 second) between prints; Task2 delays 500 ms (0.5 seconds).

2. Step 2: Understand task scheduling

   Both tasks run independently and print their messages at their own intervals, so Task2 prints twice as often as Task1.

3. Final Answer:

   Task1 running every 1 second, Task2 running every 0.5 seconds, both printing alternately. -> Option D

4. Quick Check:

   Delays control print frequency = Task1 running every 1 second, Task2 running every 0.5 seconds, both printing alternately. [OK]

Hint: Check vTaskDelay times to predict print frequency [OK]

Common Mistakes:

• Assuming tasks block each other
• Thinking Task2 stops after one print
• Ignoring delays causing print timing

4. Identify the error in this FreeRTOS task creation code:

void vTaskCode(void *pvParameters) {
  while(1) {
    // Task code
  }
}

int main() {
  xTaskCreate(vTaskCode, "Task", 1000, NULL, 1, NULL);
  vTaskStartScheduler();
  return 0;
}

medium

A. Task handle parameter is NULL, so task cannot be managed later.

B. The task function should not have an infinite loop.

C. Stack size is too large and causes memory overflow.

D. vTaskStartScheduler() is called before creating the task.

Solution

1. Step 1: Check task creation parameters

   The last parameter is the task handle pointer; passing NULL means the task handle is not stored.

2. Step 2: Understand implications of NULL task handle

   Without a task handle, the program cannot control or delete the task later, which is usually needed.

3. Final Answer:

   Task handle parameter is NULL, so task cannot be managed later. -> Option A

4. Quick Check:

   Task handle NULL means no task control [OK]

Hint: Always provide a task handle pointer to manage tasks [OK]

Common Mistakes:

• Thinking infinite loops are wrong in tasks
• Believing stack size is always too large
• Assuming scheduler starts before task creation

5. You want to design a FreeRTOS application that reads sensor data, processes it, and updates a display. Why should you use separate tasks for each job?

hard

A. To avoid using queues or synchronization mechanisms.

B. To reduce the total memory used by combining jobs in one task.

C. To ensure each job runs independently and can be scheduled without blocking others.

D. To make the program run faster by running all jobs in a single loop.

Solution

1. Step 1: Understand task separation benefits

   Separating jobs into tasks allows each to run independently and be scheduled by FreeRTOS efficiently.

2. Step 2: Recognize multitasking advantages

   This prevents one job from blocking others, improving responsiveness and reliability.

3. Final Answer:

   To ensure each job runs independently and can be scheduled without blocking others. -> Option C

4. Quick Check:

   Separate tasks = independent, non-blocking jobs [OK]

Hint: Use separate tasks to avoid blocking and improve multitasking [OK]

Common Mistakes:

• Thinking combining jobs saves memory always
• Believing single loop is faster for multitasking
• Ignoring need for synchronization with multiple tasks