Priority-based scheduling in FreeRTOS - Mini Project: Build & Apply

Priority-based scheduling

📖 Scenario: You are working on a small embedded system that uses FreeRTOS. You want to create tasks with different priorities to see how FreeRTOS schedules them.

🎯 Goal: Create three tasks with different priorities and observe how FreeRTOS runs the highest priority task first.

📋 What You'll Learn

Create three tasks named Task1, Task2, and Task3.

Assign priorities 1, 2, and 3 to Task1, Task2, and Task3 respectively.

Each task should print its name once when it runs.

Start the FreeRTOS scheduler to run the tasks.

💡 Why This Matters

🌍 Real World

Embedded systems often need to run multiple tasks with different importance levels. Priority-based scheduling helps ensure critical tasks run first.

💼 Career

Understanding FreeRTOS task priorities is essential for embedded software developers working on real-time applications like IoT devices, automotive systems, and industrial controllers.

1

Create three tasks with empty functions

Create three task functions called Task1, Task2, and Task3. Each function should have the correct FreeRTOS task signature and an infinite loop with no code inside.

FreeRTOS

void Task1(void *pvParameters) {
    for(;;) {
        // Your code here
    }
}

void Task2(void *pvParameters) {
    for(;;) {
        // Your code here
    }
}

void Task3(void *pvParameters) {
    for(;;) {
        // Your code here
    }
}

Need a hint?

Each task function must have the signature void TaskName(void *pvParameters) and an infinite loop for(;;).

2

Create task handles and add tasks with priorities

Create three task handles called xTask1Handle, xTask2Handle, and xTask3Handle. Use xTaskCreate to create Task1 with priority 1, Task2 with priority 2, and Task3 with priority 3. Use stack size 100 for all tasks and pass NULL as parameters.

FreeRTOS

void Task1(void *pvParameters) {
    for(;;) {
    }
}

void Task2(void *pvParameters) {
    for(;;) {
    }
}

void Task3(void *pvParameters) {
    for(;;) {
    }
}

TaskHandle_t xTask1Handle, xTask2Handle, xTask3Handle;

// Create tasks with priorities
// Your code here

Need a hint?

Use xTaskCreate with the correct parameters: function, name, stack size, parameters, priority, and handle.

3

Add print statements inside each task

Inside the infinite loop of each task function, add a printf statement that prints the task name: "Running Task1\n" in Task1, "Running Task2\n" in Task2, and "Running Task3\n" in Task3. Add a vTaskDelay(1000 / portTICK_PERIOD_MS); after the print to delay 1 second.

FreeRTOS

void Task1(void *pvParameters) {
    for(;;) {
        // Add printf and delay here
    }
}

void Task2(void *pvParameters) {
    for(;;) {
        // Add printf and delay here
    }
}

void Task3(void *pvParameters) {
    for(;;) {
        // Add printf and delay here
    }
}

TaskHandle_t xTask1Handle, xTask2Handle, xTask3Handle;

xTaskCreate(Task1, "Task1", 100, NULL, 1, &xTask1Handle);
xTaskCreate(Task2, "Task2", 100, NULL, 2, &xTask2Handle);
xTaskCreate(Task3, "Task3", 100, NULL, 3, &xTask3Handle);

Need a hint?

Use printf to print the task name and vTaskDelay to pause the task for 1 second.

4

Start the FreeRTOS scheduler

Add the call vTaskStartScheduler(); after creating the tasks to start the FreeRTOS scheduler.

FreeRTOS

#include 
#include "FreeRTOS.h"
#include "task.h"

void Task1(void *pvParameters) {
    for(;;) {
        printf("Running Task1\n");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

void Task2(void *pvParameters) {
    for(;;) {
        printf("Running Task2\n");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

void Task3(void *pvParameters) {
    for(;;) {
        printf("Running Task3\n");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

TaskHandle_t xTask1Handle, xTask2Handle, xTask3Handle;

xTaskCreate(Task1, "Task1", 100, NULL, 1, &xTask1Handle);
xTaskCreate(Task2, "Task2", 100, NULL, 2, &xTask2Handle);
xTaskCreate(Task3, "Task3", 100, NULL, 3, &xTask3Handle);

// Start the scheduler
// Your code here

Need a hint?

Call vTaskStartScheduler(); to start running the tasks.