Realtime Systems

In industrial automation, robotics, and CNC systems, achieving hard real-time determinism is crucial for safety, precision, and performance. Many systems rely on costly proprietary solutions to meet those demands—but OpenCN offers an open, modular alternative specifically built for embedded motion control with microsecond-level timing precision. Released under the GPLv2 license, OpenCN promotes transparency, adaptability, and long-term sustainability—making it an excellent foundation for building reliable, real-time automation systems without vendor lock-in.

OpenCN is ideal for developers and integrators looking for affordable, real-time, and production-grade control systems that don't compromise on timing guarantees or long-term maintainability.

OpenCN originates from the well-known LinuxCNC project, whose architecture has powered machine tools and motion platforms for decades. However, traditional LinuxCNC relies on either soft real-time or hybrid userspace/hard real-time setups, often with considerable complexity or overhead.

🧠 Real-Time Core: Xenomai/Cobalt, Streamlined and Evolved

At the foundation of OpenCN lies a customized hard real-time core based on Xenomai/Cobalt. Unlike traditional implementations,…

The release of Linux RT-Preempt Kernel 6.12 marks another significant step in enhancing real-time performance for critical applications. This version introduces improved low-latency scheduling, deterministic behavior, and better IRQ handling, providing a more stable foundation for industrial automation, robotics, and other real-time workloads.

With enhanced IRQ threading, latency spikes are significantly reduced, even under high-load scenarios. The improved preemptibility ensures consistent response times for real-time applications, making the system more predictable. CPU isolation techniques have also been refined, minimizing jitter and improving determinism.

Additionally, real-time scheduling policies have been optimized, increasing efficiency for time-sensitive operations.

However, some areas in the kernel still pose potential risks for latency spikes during real-time operations. For instance, the seccomp() syscall triggers a call to the tlb_flush_all() function, which invalides all TLBs on all CPUs.

On an x86 machine with an SMP configuration, this function relies on a special APIC mechanism to broadcast IPIs to all CPUs in a single instruction.…

If your embedded system requires real-time constraints, don't worry! The Linux operating system remains a top choice. With significant advancements in the upstream RT-PREEMPT extension over the past three years, you can now run applications on isolated CPU cores with minimal latency and jitter.

However, some specific use cases—particularly those requiring hard real-time performance in user-space applications—can be tricky. Combining RT and non-RT tasks in the same environment may lead to interference, and implementing non-GPL closed-source code within the kernel only adds to the complexity.

For these challenges, the EVL (Xenomai 4) extension is a powerful alternative to RT-PREEMPT. Here’s why

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• Out-of-Band (OOB) Functions: Guarantee hard real-time conditions across execution paths, ensuring deterministic behavior for critical tasks.
  

• Clean RT/Non-RT Separation: Isolates the real-time domain from standard Linux tasks, minimizing interference.
  

Have you ever thought that x86 would gradually leave the world of embedded systems?

Our Engineers are on hand to give you the necessary expertises in hard realtime systems based on Linux for your new development, if you envisage to start a new product or to port an existing realtime systems.

Hard realtime systems is the third axis of competences we have at EDGEMTech.

It concerns all aspects (development, tuning and optimization, porting, debugging, etc.) related to hard realtime systems (mainly x86 and ARM Linux-based systems).

Do not hesitate to contact our expert Daniel Rossier for any advice.