STM32 FreeRTOS: Introduction to FreeRTOS

FreeRTOS is a lightweight, deterministic real-time operating system (RTOS) designed for microcontrollers and small embedded processors where timing, reliability, and resource efficiency are critical. Unlike general-purpose operating systems, FreeRTOS provides a minimal kernel focused on predictable task scheduling, fast interrupt response, and low memory footprint, making it well suited for motor control, robotics, automotive, and IoT devices. It enables developers to structure firmware as multiple concurrent tasks instead of a single super-loop, improving modularity and maintainability while still meeting strict real-time deadlines. The kernel offers essential synchronization and communication mechanisms such as queues, semaphores, mutexes, software timers, and event groups, allowing safe data exchange between tasks and interrupt service routines. Because it is portable across many architectures and integrates easily with vendor SDKs, FreeRTOS has become one of the most widely adopted foundations for modern embedded real-time software.

Scheduling & Execution Model

• Supports preemptive, cooperative, and time-slice scheduling
• Supports real-time tasks and co-routines
• Unlimited number of tasks
• Unlimited priority levels

Memory & Footprint

• Very small kernel footprint (typically 4–9 KB RAM)
• Components can use static or dynamic memory allocation
• Written mainly in C language for portability
• Portable across 30+ CPU architectures

Power & Efficiency

• Provides Tickless mode for low-power applications
• Efficient software timers
• Optimized for small microcontrollers

Inter-Task Communication & Synchronization

• Task notifications
• Message queues
• Binary semaphores
• Counting semaphores
• Recursive mutexes
• Mutexes with priority inheritance
• Event groups (event flags)

Safety & Reliability

• Stack overflow detection
• Strong execution tracing capability
• MPU support on Cortex-M (e.g., STM32F429, STM32F407)
• SafeRTOS derived version available for higher code integrity

Reference
[1] FreeRTOS
[2] FreeRTOS LTS Libraries
[3] Beginner’s guides to FreeRTOS
[4] FreeRTOS Documentation
[5] FreeRTOS Book Examples