Introduction to FreeRTOS and Its Industry Applications

Table of Contents

• 1.1 RTOS Concepts vs Bare-Metal Development
• 1.1.1 Characteristics of Bare-Metal Development
• 1.1.2 Core Concepts of RTOS
• 1.1.3 Comparative Summary
• 1.2 FreeRTOS Architecture and Open Source License
• 1.2.1 System Architecture
• 1.2.2 Open Source License Analysis
• 1.2.3 Typical Application Scenarios
• Experimental Suggestions

1.1 RTOS Concepts vs Bare-Metal Development

1.1.1 Characteristics of Bare-Metal Development

// Example of typical bare-metal code structure
void main() {
    while(1) {
        task1(); // Task 1
        task2(); // Task 2
        task3(); // Task 3
    }
}

• Polling Architecture: Sequential execution of all tasks
• Simplicity: No scheduling overhead, direct hardware control
• Limitations:
• Real-time latency (high-priority tasks cannot preempt)
• Task blocking leads to system stagnation
• Resource utilization issues (CPU often in busy-wait state)

1.1.2 Core Concepts of RTOS

// Example of FreeRTOS task creation
xTaskCreate(taskFunction, "Task", configMINIMAL_STACK_SIZE, NULL, 1, NULL);

• Task Scheduling:
• Priority preemptive scheduling
• Time-slicing (for same priority)
• System Services:
• Inter-task communication (queues/semaphores)
• Memory management
• Timer services
• Real-time Guarantees:
• Deterministic task response times
• Worst-case execution time (WCET) is predictable

1.1.3 Comparative Summary

Feature	Bare-Metal System	RTOS System
Response Speed	Depends on code order	µs-level task switching
Multi-tasking	Requires manual polling	Native support
Resource Usage	Minimal (1-2KB RAM)	Typically requires 4-10KB RAM
Development Complexity	Simple	Requires understanding of RTOS concepts
Application Scenarios	Simple control logic	Complex multi-tasking systems

1.2 FreeRTOS Architecture and Open Source License

1.2.1 System Architecture

FreeRTOS Core Components
├── Task Scheduler
│   ├── Priority Preemptive
│   └── Cooperative (optional)
├── Memory Management
│   ├── heap_1~5
│   └── User-defined
├── Communication Mechanisms
│   ├── Queue
│   ├── Semaphore
│   └── Mutex
└── Hardware Abstraction Layer
    ├── Port Layer
    └── Clock Management

1.2.2 Open Source License Analysis

• MIT License Core Features:

  1. Allows commercial use
  2. Modifications must retain copyright notice
  3. No warranty liability
  4. Prohibition on using the author's name for promotion
  

• Commercial Application Considerations:
• Modified versions do not need to be open source
• Must acknowledge use of FreeRTOS in documentation/About screen
• Recommended to use the official CMSIS-RTOS v2 compatibility layer

1.2.3 Typical Application Scenarios

1. Industrial Control

• PLC Controllers (multi-task real-time scheduling)
• Motion Control (precise timing guarantees)

Consumer Electronics

• Smart Home Devices (low power management)
• Wearable Devices (memory optimization)

Automotive Electronics

• ECU Units (ASIL-B certified versions)
• In-vehicle Infotainment (multi-core expansion)

Internet of Things

• Edge Computing Nodes (LwIP + FreeRTOS)
• Wireless Sensors (low-power tickless mode)

Experimental Suggestions

Experiment 1.1: Create two tasks with different priorities and observe preemption behavior.Experiment 1.2: Measure context switching time using GPIO and an oscilloscope.