Static vs dynamic allocation (configSUPPORT_STATIC_ALLOCATION) in FreeRTOS - Hands-On Comparison

Static vs Dynamic Allocation in FreeRTOS

📖 Scenario: You are working on a small embedded system project using FreeRTOS. You need to create a task that blinks an LED. You want to understand how to create this task using both static and dynamic memory allocation methods.

🎯 Goal: Build a FreeRTOS program that creates a task to blink an LED using static allocation first, then add a configuration variable to switch between static and dynamic allocation, and finally implement the task creation logic accordingly. You will print a message to confirm which allocation method is used.

📋 What You'll Learn

Create a task control block and stack for static allocation

Add a configuration variable configSUPPORT_STATIC_ALLOCATION to enable or disable static allocation

Use xTaskCreateStatic when static allocation is enabled and xTaskCreate when disabled

Print the allocation method used

💡 Why This Matters

🌍 Real World

Embedded systems often have limited memory. Choosing static or dynamic allocation affects memory usage and system stability.

💼 Career

Understanding FreeRTOS task creation and memory allocation is essential for embedded software developers working on real-time applications.

1

Create static task control block and stack

Create a static task control block called xTaskBuffer and a static stack array called xStack with size 128 for the task.

FreeRTOS

# Create a static task control block and stack array
// Your code here

Need a hint?

Use StaticTask_t for the task control block and StackType_t array for the stack.

2

Add configSUPPORT_STATIC_ALLOCATION variable

Create a constant integer variable called configSUPPORT_STATIC_ALLOCATION and set it to 1 to enable static allocation.

FreeRTOS

StaticTask_t xTaskBuffer;
StackType_t xStack[128];
// Define configSUPPORT_STATIC_ALLOCATION variable
// Your code here

Need a hint?

Use const int to define the configuration variable.

3

Create the task using static or dynamic allocation

Write code to create a task called vBlinkTask with priority 1 and stack size 128. Use xTaskCreateStatic if configSUPPORT_STATIC_ALLOCATION is 1, otherwise use xTaskCreate. Use xTaskBuffer and xStack for static allocation parameters.

FreeRTOS

StaticTask_t xTaskBuffer;
StackType_t xStack[128];
const int configSUPPORT_STATIC_ALLOCATION = 1;

// Create the task using static or dynamic allocation
// Your code here

Need a hint?

Use an if statement to choose between xTaskCreateStatic and xTaskCreate.

4

Print which allocation method is used

Print "Using static allocation" if configSUPPORT_STATIC_ALLOCATION is 1, otherwise print "Using dynamic allocation".

FreeRTOS

StaticTask_t xTaskBuffer;
StackType_t xStack[128];
const int configSUPPORT_STATIC_ALLOCATION = 1;

void vBlinkTask(void *pvParameters) {
    for(;;) {
        // Toggle LED code here
        vTaskDelay(pdMS_TO_TICKS(500));
    }
}

TaskHandle_t xHandle = NULL;
if (configSUPPORT_STATIC_ALLOCATION == 1) {
    xHandle = xTaskCreateStatic(
        vBlinkTask,
        "Blink",
        128,
        NULL,
        1,
        xStack,
        &xTaskBuffer
    );
} else {
    xTaskCreate(
        vBlinkTask,
        "Blink",
        128,
        NULL,
        1,
        &xHandle
    );
}

// Print allocation method
// Your code here

Need a hint?

Use printf inside the if and else blocks to print the messages.