In embedded systems development, FreeRTOS on ARM Cortex-M3 provides a structured approach to handling multitasking efficiently. Understanding how the kernel manages tasks, priorities, and synchronization helps you design predictable and responsive applications.
FreeRTOS on ARM Cortex-M3
provides lightweight real-time scheduling, flexible task management, and reliable inter-task communication. This makes it ideal for applications such as motor control, IoT devices, and industrial automation where precise timing and deterministic behavior are essential.
FreeRTOS is a lightweight real-time operating system (RTOS) specifically designed for microcontrollers, such as the ARM Cortex-M3. It allows you to break your application into independent tasks (threads) that run seemingly in parallel. These tasks can safely share data using queues, semaphores, and mutexes, while the FreeRTOS kernel handles preemptive or cooperative scheduling in the background.
On a single-core processor like the LPC1768, only one task executes at any given moment. The FreeRTOS scheduler switches between tasks based on priority and time slicing, minimizing jitter for critical real-time operations.
| Feature | Benefit |
|---|---|
| CPU Performance | ARM Cortex-M3 @ 100 MHz, deterministic interrupt latency |
| Peripherals | GPIO, UART, SPI, I²C, CAN, USB – ideal for real-time systems |
| Portability | Same FreeRTOS logic works across STM32, LPC, and other Cortex-M3 MCUs |
| Community Support | Mature FreeRTOS port with examples and documentation |
The FreeRTOS ARM Cortex M3 port for LPC1768 includes all standard FreeRTOS features:
FreeRTOS also supports interrupt nesting, allowing high-priority interrupts to run without being delayed by the kernel, ensuring minimal timing jitter.
Visit: http://www.freertos.org/a00104.html
Download the ZIP file and extract it to a convenient location.
This guide uses FreeRTOS v9.0.0.
From the extracted FreeRTOS directory, copy the following:
From: FreeRTOSv9.0.0\FreeRTOS\Source\include
Copy:
From: FreeRTOSv9.0.0\FreeRTOS\Source
Copy:
EXTERN vPortSVCHandler
EXTERN xPortPendSVHandler
EXTERN xPortSysTickHandler
Update the vector table mappings: - SVC_Handler → vPortSVCHandler - PendSV_Handler → xPortPendSVHandler - SysTick_Handler → xPortSysTickHandler
The FreeRTOSConfig.h file defines application-specific kernel settings, such as:
You can start by editing an existing configuration file from a demo project, for example:
FreeRTOSv9.0.0\FreeRTOS\Demo\CORTEX_LPC1768_GCC_RedSuite\src
Using FreeRTOS ARM Cortex M3 on the LPC1768 allows you to develop reliable, real-time embedded applications. With proper setup in Keil and a well-tuned FreeRTOSConfig.h you can efficiently manage multiple tasks, handle interrupts, and meet strict timing requirements in your embedded designs.
FreeRTOS is a lightweight, open-source real-time operating system that enables multitasking on microcontrollers like ARM Cortex-M3. It helps manage multiple tasks efficiently, making it ideal for embedded systems development.
Yes, FreeRTOS fully supports LPC1768 microcontrollers. You can develop and debug your FreeRTOS projects using Keil µVision by including the FreeRTOS source files and configuring the system tick timer.
FreeRTOS offers multiple heap allocation schemes (heap_1.c to heap_5.c). For most ARM Cortex-M3 LPC1768 projects, heap_4.c is recommended because it provides memory allocation and deallocation with minimal fragmentation.
FreeRTOS itself is very lightweight, typically requiring only a few kilobytes of RAM and Flash. However, the actual memory usage depends on the number of tasks, stack sizes, and enabled features.
Yes, FreeRTOS is highly portable. With minor changes to the hardware abstraction layer and board-specific code, you can run your project on other ARM Cortex-M or even non-ARM microcontrollers.
Yes, FreeRTOS integrates with ARM Cortex-M3 NVIC interrupts. You can use ISRs alongside tasks, but you must follow FreeRTOS interrupt-safe API rules to avoid priority and timing issues.
Yes, but you should use the officially certified FreeRTOS Safety Kernel if you are working on applications requiring IEC 61508, ISO 26262, or similar safety standards compliance.