FreeRTOS architecture overview - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Core components of FreeRTOS

Which of the following is NOT a core component of the FreeRTOS architecture?

A Memory management unit (MMU)

B Task scheduler

C Queues for inter-task communication

D Software timers

💡 Hint

Think about what FreeRTOS provides for multitasking and communication, and what hardware features it does not include.

FreeRTOS includes a task scheduler, queues, and software timers as core components. The Memory Management Unit (MMU) is a hardware feature, not part of FreeRTOS architecture.

❓ Predict Output

intermediate

FreeRTOS task states output

Given the following FreeRTOS task state code snippet, what will be the output?

FreeRTOS

eTaskState state = eRunning;

switch(state) {
    case eRunning:
        printf("Task is running\n");
        break;
    case eReady:
        printf("Task is ready\n");
        break;
    case eBlocked:
        printf("Task is blocked\n");
        break;
    default:
        printf("Unknown state\n");
}

A Unknown state

B Task is ready

C Task is blocked

D Task is running

💡 Hint

Look at the value assigned to state and which case it matches.

The variable state is set to eRunning, so the output is "Task is running".

🔧 Debug

advanced

Diagnosing priority inversion in FreeRTOS

Consider a FreeRTOS system where a low priority task holds a mutex, and a high priority task is blocked waiting for it. What problem is this an example of?

A Priority inversion

B Deadlock

C Starvation

D Race condition

💡 Hint

Think about what happens when a higher priority task waits for a resource held by a lower priority task.

This is a classic example of priority inversion, where a high priority task is blocked by a lower priority task holding a resource.

📝 Syntax

advanced

Correct FreeRTOS task creation syntax

Which of the following code snippets correctly creates a FreeRTOS task?

A xTaskCreate(TaskFunction, Task1, 1000, NULL, 2, NULL);

B xTaskCreate(TaskFunction, "Task1", 1000, NULL, 2, NULL);

C xTaskCreate(TaskFunction, "Task1", 1000, NULL, "2", NULL);

D xTaskCreate(TaskFunction, "Task1", 1000, NULL);

💡 Hint

Check the function parameters and their types carefully.

Option B uses the correct syntax with a string task name, stack size, parameters, priority as integer, and task handle pointer.

🚀 Application

expert

Determining FreeRTOS queue length after operations

A FreeRTOS queue is created with length 3. The following operations occur in order:

1. Send one item to the queue
2. Receive one item from the queue
3. Send two items to the queue
4. Receive one item from the queue

How many items remain in the queue after these operations?

A 3

B 2

C 1

D 0

💡 Hint

Track the queue count step-by-step after each send and receive.

Step 1: queue has 1 item
Step 2: queue has 0 items
Step 3: queue has 2 items
Step 4: queue has 1 item remaining