xTaskNotify() with value in FreeRTOS - Mini Project: Build & Apply

Using xTaskNotify() with Value in FreeRTOS

📖 Scenario: You are working on a FreeRTOS-based embedded system where two tasks need to communicate. One task will send a notification with a value to another task to trigger an action.

🎯 Goal: Build a simple FreeRTOS program where TaskSender sends a notification with a value to TaskReceiver using xTaskNotify(). The receiver task will print the received value.

📋 What You'll Learn

Create two tasks: TaskSender and TaskReceiver

Use xTaskNotify() to send a value from TaskSender to TaskReceiver

Use xTaskNotifyWait() in TaskReceiver to receive the notification and value

Print the received notification value in TaskReceiver

💡 Why This Matters

🌍 Real World

Task notifications with values are used in embedded systems to signal events or pass small data between tasks efficiently.

💼 Career

Understanding task notifications is essential for embedded software developers working with FreeRTOS to build responsive and efficient multitasking applications.

1

Create Task Handles

Declare two task handles called TaskSenderHandle and TaskReceiverHandle initialized to NULL.

FreeRTOS

// Declare task handles
// Your code here

Need a hint?

Task handles are pointers used to identify tasks in FreeRTOS. Initialize them to NULL.

2

Create TaskReceiver Task Function

Write a task function called TaskReceiver that waits for a notification using xTaskNotifyWait() and stores the received value in a variable called receivedValue.

FreeRTOS

TaskHandle_t TaskSenderHandle = NULL;
TaskHandle_t TaskReceiverHandle = NULL;

// Define TaskReceiver function
// Your code here

Need a hint?

Use xTaskNotifyWait() with clear bits 0x00, clear all bits on exit 0xffffffff, and wait forever portMAX_DELAY.

3

Create TaskSender Task Function and Send Notification

Write a task function called TaskSender that sends a notification with the value 123 to TaskReceiverHandle using xTaskNotify() with the action eSetValueWithOverwrite.

FreeRTOS

TaskHandle_t TaskSenderHandle = NULL;
TaskHandle_t TaskReceiverHandle = NULL;

void TaskReceiver(void *pvParameters) {
    uint32_t receivedValue = 0;
    for (;;) {
        xTaskNotifyWait(0x00, 0xffffffff, &receivedValue, portMAX_DELAY);
        // Process receivedValue here
    }
}

// Define TaskSender function
// Your code here

Need a hint?

Use vTaskDelay() to wait 1000 milliseconds between notifications.

4

Print Received Value in TaskReceiver

Add a printf statement inside TaskReceiver after xTaskNotifyWait() to print the received value in the format: "Received notification value: %lu\n".

FreeRTOS

TaskHandle_t TaskSenderHandle = NULL;
TaskHandle_t TaskReceiverHandle = NULL;

void TaskReceiver(void *pvParameters) {
    uint32_t receivedValue = 0;
    for (;;) {
        xTaskNotifyWait(0x00, 0xffffffff, &receivedValue, portMAX_DELAY);
        // Print received value here
    }
}

void TaskSender(void *pvParameters) {
    for (;;) {
        xTaskNotify(TaskReceiverHandle, 123, eSetValueWithOverwrite);
        vTaskDelay(pdMS_TO_TICKS(1000));
    }
}

Need a hint?

Use printf to show the value received from the notification.