Leading the Embedded World

A safe, secure, and lean OS

The μ-velOSity real-time operating system (RTOS) is the smallest of Green Hills Software’s family of RTOSes. It supports a wide range of microcontroller architectures and is being certified at the highest levels of industry standards for functional safety and security. Its streamlined design and tight integration with the MULTI integrated development environment (IDE) make μ-velOSity both easy-to-learn and simple-to-use. Embedded devlopers using it can build sophisticated solutions for automotive, industrial, IoT and other applications.

For over 40 years, Green Hills Software has been providing software products and services for mission-critical embedded systems in diverse market segments. In this decades-long journey, Green Hills Software has built the μ-velOSity RTOS to meet industry requirements for a safe, secure, lean, and reliable operating system for embedded microcontrollers.

Reliable microkernel architecture

At the heart of the μ-velOSity RTOS is an efficient and reliable kernel with a minimal footprint and a concise API. Essential features include:

  • safety- and security-certified
  • memory protection
  • fast boot
  • fast execution
  • simple API

μ-velOSity enables applications, middleware, and drivers to run outside of kernel memory space. This optional memory protection is made possible by leveraging the Arm architecture’s Memory Protection Unit (MPU). The resulting isolation provides the foundation for safety and security, allowing system designers to meet freedom-from-interference requirements between critical and non-critical applications.

The μ-velOSity RTOS comes with three predefined build configurations—optimized for speed, optimized for size, or optimized for debug—which enable developers to quickly adjust RTOS behavior. Additional build configurations can be created and customized to meet specific project requirements.

The µ-velOSity RTOS features a unique architecture in which applications, middleware and drivers all run outside of the kernel.

Memory protection

The μ-velOSity RTOS allows applications, drivers, and middleware to run outside of the kernel memory space. The μ-velOSity RTOS’ MPU support allows memory to be partitioned into several distinct regions which guarantees the safe and secure isolation of tasks assigned to those regions.


µ-velOSity implements a priority-based, pre-emptive scheduler to improve real-time response to events for critical tasks with elevated priorities. The highest-priority task always gets control over the resource first.

Message queues

The μ-velOSity RTOS’ message queue mechanism provides efficient task communication and synchronization. Information can be sent quickly—vital for performance-sensitive applications.


The μ-velOSity RTOS is being certified to multiple industry standards, enabling system designers to reduce both project software cost and time-to-market. These certifications include:

  • Secure Element-out-of-Context:
    - ISO 21434 (automotive security)
  • Safety Element-out-of-Context (SEooC):
    - ISO 26262 ASIL D (automotive)
    - IEC 61508 SIL 3 (industrial)
    - EN 50128 SIL 4 (railway)

Processor Support

µ-velOSity provides out-of-the-box support for:

  • Arm v7-M: Cortex-M4(F) with MPU; Cortex-M7(F) with MPU
  • Arm v7-R: Cortex-R5(F) with MPU
  • Arm v8-R: Cortex-R52 with MPU
  • RISC-V: RV32 IMC extended instruction set

Additional hardware architectures are planned for future releases.

State-of-the-art development tools

Green Hills Software has been providing tools for developing and debugging embedded systems for over 40 years. With µ-velOSity, you can leverage the most comprehensive suite of embedded development tools available to realize complete application control and visibility. These include:

  • MULTI development tools µ-velOSity include simultaneous multiple task debugging integrated with profiling and code coverage visibility for advanced source-level debugging.
  • Optimizing compilers for C, C++, Embedded C++ and MISRA C generate the smallest-footprint and fastest-executing code in the industry.
  • Target simulation to provide instruction-accurate, host-based simulation environments for µ-velOSity when hardware is not yet available or in limited supply.
  • New Project Wizard for µ-velOSity provides project templates and application examples to help users get up and running with µ-velOSity in minutes.
  • Green Hills Probes for multicore hardware bring-up, low-level debugging, and trace-powered analysis debugging.
Green Hills advanced embedded development tools

Green Hills has developed the next-generation of tools for end customers developing and delivering complex embedded solutions.

Reliable solution for safety & security

Modern microcontrollers in automotive, industrial and IoT applications need an RTOS purpose-built for the task. Vehicle electronics are a good example where cyber security, functional safety, cost, and scalability are OEM priorities for ECU node applications with ultra-small memory footprint requirements.

On one hand, the RTOS must enable applications to fit in the limited internal-only memory of microcontrollers. On the other, the RTOS must provide application-layer enablement for new domain-specific hardware features of modern microcontrollers and expose a unified application interface across different core architectures and silicon solutions. Finally, the software solution built on the RTOS must be certified to the highest levels of safety and security. The µ-velOSity RTOS from Green Hills Software fulfills all these requirements.

The µ-velOSity RTOS and platform are also a perfect complement to the traditional use of AUTOSAR Classic in that they can cover a different class of applications, memory footprint, performance, and features.

Automotive Applications

Applications µ-velOSity is ideal for include:

  • smart e-fuses
  • drive mechanics
  • zonal and domain controllers
  • battery management systems (BMS)
  • communication modules
  • radar
  • safety islands/safety checker
  • traction, braking, and steering systems
  • and many more