Stack high water mark monitoring in FreeRTOS - Mini Project: Build & Apply

Stack High Water Mark Monitoring in FreeRTOS

📖 Scenario: You are working on a FreeRTOS-based embedded system. To ensure your tasks have enough stack memory, you want to monitor the stack high water mark for a specific task. This helps prevent stack overflow and system crashes.

🎯 Goal: Build a simple FreeRTOS program that creates a task and monitors its stack high water mark using the uxTaskGetStackHighWaterMark API. You will print the high water mark value to check how much stack space remains unused.

📋 What You'll Learn

Create a FreeRTOS task function named vExampleTask.

Create a task handle variable named xExampleTaskHandle.

Create the task with xTaskCreate using vExampleTask and store the handle in xExampleTaskHandle.

Declare a variable uxHighWaterMark to hold the stack high water mark.

Use uxTaskGetStackHighWaterMark(xExampleTaskHandle) to get the high water mark.

Print the high water mark value using printf.

💡 Why This Matters

🌍 Real World

Embedded developers use stack high water mark monitoring to ensure tasks have enough memory and avoid crashes.

💼 Career

Understanding FreeRTOS stack monitoring is essential for embedded systems engineers and IoT developers to build reliable applications.

1

Create the example task and task handle

Create a task function called vExampleTask that runs an infinite loop with vTaskDelay(1000 / portTICK_PERIOD_MS). Also, declare a task handle variable called xExampleTaskHandle initialized to NULL.

FreeRTOS

// Your code here

Need a hint?

Define the task function with an infinite loop and delay. Declare the task handle variable outside the function.

2

Create the task and store its handle

Use xTaskCreate to create the task vExampleTask with name "ExampleTask", stack size configMINIMAL_STACK_SIZE, no parameters, priority tskIDLE_PRIORITY + 1, and store the task handle in xExampleTaskHandle.

FreeRTOS

void vExampleTask(void *pvParameters) {
    for (;;) {
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

TaskHandle_t xExampleTaskHandle = NULL;

// Create the task below

Need a hint?

Use xTaskCreate with the exact parameters and start the scheduler with vTaskStartScheduler().

3

Get the stack high water mark

Declare a variable uxHighWaterMark of type UBaseType_t. Assign it the value returned by uxTaskGetStackHighWaterMark(xExampleTaskHandle).

FreeRTOS

void vExampleTask(void *pvParameters) {
    for (;;) {
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

TaskHandle_t xExampleTaskHandle = NULL;

void main_app(void) {
    xTaskCreate(vExampleTask, "ExampleTask", configMINIMAL_STACK_SIZE, NULL, tskIDLE_PRIORITY + 1, &xExampleTaskHandle);
    
    // Declare and assign uxHighWaterMark below

    vTaskStartScheduler();
}

Need a hint?

Use the FreeRTOS API uxTaskGetStackHighWaterMark with the task handle to get the high water mark.

4

Print the stack high water mark

Add a printf statement to print the text "Stack high water mark: " followed by the value of uxHighWaterMark inside main_app before vTaskStartScheduler().

FreeRTOS

void vExampleTask(void *pvParameters) {
    for (;;) {
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

TaskHandle_t xExampleTaskHandle = NULL;

void main_app(void) {
    xTaskCreate(vExampleTask, "ExampleTask", configMINIMAL_STACK_SIZE, NULL, tskIDLE_PRIORITY + 1, &xExampleTaskHandle);
    UBaseType_t uxHighWaterMark = uxTaskGetStackHighWaterMark(xExampleTaskHandle);
    
    // Print the stack high water mark below

    vTaskStartScheduler();
}

Need a hint?

Use printf with %u to print the unsigned integer value of uxHighWaterMark.