Bare-metal vs RTOS execution model in Embedded C - Hands-On Comparison

Bare-metal vs RTOS Execution Model

📖 Scenario: You are working on a simple embedded system that controls two LEDs. One LED should blink slowly, and the other should blink quickly. You want to understand the difference between running this on a bare-metal system (without an operating system) and using a Real-Time Operating System (RTOS) to manage tasks.

🎯 Goal: Build two versions of the LED blinking program: one using a bare-metal approach with a simple loop and delays, and another using an RTOS with two separate tasks. This will help you see how the execution models differ.

📋 What You'll Learn

Create variables to represent LED states

Implement a delay function

Write a bare-metal loop to blink LEDs

Write RTOS tasks to blink LEDs concurrently

Print LED states to simulate blinking

💡 Why This Matters

🌍 Real World

Embedded systems often control hardware like LEDs, motors, or sensors. Understanding bare-metal and RTOS models helps design efficient and responsive devices.

💼 Career

Embedded software engineers must know how to write code for microcontrollers both with and without operating systems to meet project requirements.

1

Setup LED state variables

Create two integer variables called led_slow and led_fast and initialize both to 0 to represent LEDs being off.

Embedded C

# Create two integer variables led_slow and led_fast and set both to 0
# Your code here

Need a hint?

Use int to declare variables and set them to 0.

2

Add delay function

Write a function called delay that takes an integer count and uses a simple empty loop to create a delay.

Embedded C

int led_slow = 0;
int led_fast = 0;

// Write a delay function that loops count times
void delay(int count) {
    // Your code here
}

Need a hint?

Use a for loop inside the delay function to waste time.

3

Write bare-metal LED blinking loop

Write a main function that uses an infinite while loop to toggle led_slow every 1000000 counts and led_fast every 500000 counts using the delay function. Toggle means change 0 to 1 or 1 to 0.

Embedded C

int led_slow = 0;
int led_fast = 0;

void delay(int count) {
    for (int i = 0; i < count; i++) {
        // empty loop for delay
    }
}

// Write main function with infinite loop to toggle LEDs with delays
int main() {
    // Your code here
}

Need a hint?

Use while (1) for an infinite loop and toggle LEDs using led = !led;.

4

Simulate RTOS tasks for LED blinking

Write two functions called task_slow and task_fast that toggle led_slow and led_fast respectively with delays of 1000000 and 500000 counts. Then write a main function that calls these two tasks alternately in an infinite loop and prints the LED states after each toggle using printf.

Embedded C

int led_slow = 0;
int led_fast = 0;

void delay(int count) {
    for (int i = 0; i < count; i++) {
        // empty loop for delay
    }
}

// Write task_slow to toggle led_slow with delay
void task_slow() {
    // Your code here
}

// Write task_fast to toggle led_fast with delay
void task_fast() {
    // Your code here
}

// Write main to call task_slow and task_fast alternately and print LED states
int main() {
    // Your code here
}

Need a hint?

Each task toggles its LED, delays, then prints the state. The main loop calls both tasks repeatedly.