Learning Objectives

• Explain what a Real-Time Operating System (RTOS) is and why it is used.
• Create and run multiple concurrent tasks using FreeRTOS.
• Describe basic task scheduling and priority concepts.

8.1 Why Use an RTOS?

A single loop() is suitable for simple programs, but more complex embedded applications may have several activities operating at different rates. An RTOS provides a structure for managing multiple tasks and scheduling their execution.

8.2 Important RTOS Terms

Figure 8.1: Original block diagram showing two concurrent FreeRTOS tasks.

8.3 Practical Activity: Multi-Task Blink & Sensor Monitor

The module specifies an ESP32 or another FreeRTOS-capable board, an LED, buzzer and potentiometer. The following is a simple ESP32 teaching example.

1. Prepare the ESP32, LED, 220 Ω resistor, potentiometer, breadboard and jumper wires.
2. Connect the LED to a digital output through the resistor.
3. Connect the potentiometer wiper to an analog input; the example uses GPIO34.
4. Create Task A to toggle the LED every 500 ms using vTaskDelay().
5. Create Task B to read the potentiometer every 1 second and print the value.
6. Start both tasks and verify that they operate concurrently.
7. Change Task A priority with trainer guidance and record observations.
8. Document the difference between this structure and a single-loop program.

Example ESP32 FreeRTOS Program

const int LED_PIN = 2;
const int POT_PIN = 34;

void taskBlink(void *parameter) {
  pinMode(LED_PIN, OUTPUT);
  while (true) {
    digitalWrite(LED_PIN, !digitalRead(LED_PIN));
    vTaskDelay(pdMS_TO_TICKS(500));
  }
}

void taskReadPot(void *parameter) {
  while (true) {
    int value = analogRead(POT_PIN);
    Serial.print(“Potentiometer value: “);
    Serial.println(value);
    vTaskDelay(pdMS_TO_TICKS(1000));
  }
}

void setup() {
  Serial.begin(115200);

  xTaskCreate(taskBlink, “Blink Task”, 2048, NULL, 1, NULL);
  xTaskCreate(taskReadPot, “Sensor Task”, 2048, NULL, 1, NULL);
}

void loop() {
  // Tasks perform the main work.
}

Teaching example: exact FreeRTOS setup can depend on the board and Arduino environment. Use the trainer’s board configuration and verify the actual hardware pins.

8.4 Single Loop versus RTOS Tasks

8.5 Practical Questions

1. Which task controls the LED?
2. How often is the potentiometer read?
3. What is the role of vTaskDelay()?
4. What does the scheduler do?
5. What might happen if one task has a higher priority?
6. Why can two tasks appear to operate at the same time?

8.6 Checkpoint

Demonstrate that both tasks run correctly and explain, in simple terms, what a task and the scheduler are doing.