Trace hooks and FreeRTOS+Trace - Mini Project: Build & Apply

Trace hooks and FreeRTOS+Trace

📖 Scenario: You are working on a FreeRTOS embedded project. You want to monitor task switches and system events to understand how your tasks run in real time.

🎯 Goal: Set up trace hooks in FreeRTOS to log task switches and use FreeRTOS+Trace to capture and display trace data.

📋 What You'll Learn

Create a trace hook function to log task switches

Define a variable to count the number of task switches

Use the trace hook to increment the counter on each switch

Print the total number of task switches after running tasks

💡 Why This Matters

🌍 Real World

Trace hooks help embedded developers monitor task behavior and timing in real-time systems.

💼 Career

Understanding trace hooks and FreeRTOS+Trace is valuable for embedded software engineers working on real-time operating systems.

1

Create a trace hook function

Write a function called vTraceTaskSwitchHook that takes no parameters and returns void. Inside, add a comment // Trace hook called on task switch.

FreeRTOS

void vTraceTaskSwitchHook(void) {
    // Trace hook called on task switch
    // Your code here
}

Need a hint?

This function will be called by FreeRTOS on every task switch.

2

Add a counter variable for task switches

Declare a global variable called ulTaskSwitchCount of type unsigned long and initialize it to 0.

FreeRTOS

unsigned long ulTaskSwitchCount = 0;

void vTraceTaskSwitchHook(void) {
    // Trace hook called on task switch
    // Your code here
}

Need a hint?

This variable will keep track of how many times tasks switch.

3

Increment the counter in the trace hook

Inside the vTraceTaskSwitchHook function, add a line to increment ulTaskSwitchCount by 1.

FreeRTOS

unsigned long ulTaskSwitchCount = 0;

void vTraceTaskSwitchHook(void) {
    // Trace hook called on task switch
    // Your code here
}

Need a hint?

Each time the hook runs, increase the counter by one.

4

Print the total task switches

Write a main function that calls vTraceTaskSwitchHook three times to simulate task switches, then prints ulTaskSwitchCount using printf with the exact format: "Total task switches: %lu\n".

FreeRTOS

unsigned long ulTaskSwitchCount = 0;

void vTraceTaskSwitchHook(void) {
    // Trace hook called on task switch
    ulTaskSwitchCount++;
}

int main(void) {
    // Your code here
}

Need a hint?

Call the hook three times and print the counter to see the total switches.