Real-Time Kernel: µC/OS 5

µC/OS 5 is the latest in a storied line of real-time kernels from Micrium. Offering highly efficient multi-tasking capabilties, it is the foundation of Micrium OS.

Key Benefits


µC/OS 5 is based on the scheduler at the heart of the highly popular µC/OS-III kernel, and many of the µC/OS 5 API functions trace their roots back to the original µC/OS, which was released in 1992.


µC/OS 5 can accomodate any number of tasks and kernel objects. The kernel's memory footprint can be adjusted to reflect the needs of application code, with a typical code footprint of well under 20 kBytes.


 The µC/OS-II kernel that preceded µC/OS 5 has been a popular choice for safety-critical systems since it was first used in a DO-178B-certified aerospace system in 2000. Many of the lessons that Micrium's team has learned while supporting µC/OS-II have strongly influnced the design and implementation of susequently released software modules, including µC/OS 5.


 Functions and macros for collecting a variety of run-time statistics have been implemented within µC/OS 5. Developers can leverage this code to identify performance bottlenecks and optimize power usage.

Kernel Features

Main Features

  • Preemptive multitasking real-time kernel with optional round-robin scheduling
  • Delivered as clean and consistent source code with in-depth documentation
  • Highly scalable, with support for an unlimited number of tasks, priorities and kernel objects
  • Resource-efficient: 6 to 24 kBytes code space and 2 kBytes (min) data space
  • Optimized interrupt-disable time
  • Built-in performance measurement capabilities

Memory Footprint

  • Scalable: Yes (compile-time and run-time configurable)
  • ROM: (Min-Max) 6–24 kBytes
  • RAM: 2+ kBytes

Task Management

  • Multitasking model - Preemptive
  • Maximum number of tasks - Unlimited
  • Scheduling - Real-time scheduler; Round-robin scheduler
  • Run-time stack checking - Configurable
  • Catch/delete tasks that return - Yes
  • Kernal timebase - Configurable (static and dynamic tick rate)
  • Timeout on calls - Yes (prevents deadlocks)

Kernal Services

  • Critical sections
  • Event Flags
  • Lock/Unlock scheduler
  • Memory partitions (prevents fragmentation)
  • Message queues
  • Monitors
  • Mutual exclusion semaphores (priority inheritance)
  • Semaphores
  • Software timers
  • Task registers
  • Task suspend/resume


Free Commercial Licenses on Silicon Labs MCUs!

µC/OS 5 is entirely free on EFM32 and EFR32 devices! Developers whose projects are based on these devices can take advantage of Micrium's latest professional-quality, real-time kernel without paying any licensing fees. All that's needed to get started with the kernel is to download the Simplicity Studio IDE and install the µC/OS 5 package. Check out our licensing page for more information.

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