THREADX RTOS EVOLUTION

THREADX is a highly deterministic Real-Time Operating System (RTOS) designed for deeply embedded, high-performance applications. The name comes from combining “threads” and a stylized symbol “X” representing context-switching. The “thread” in the name is especially important since “threads” traditionally are semi-independent program elements that share the same address space, which is the case in THREADX.

It is used in many SoC chipsets, including those found in smartphones. THREADX is also found in wearables, medical devices, printers, and automotive applications. As of 2021, per VDC Research, THREADX has achieved over 10 billion deployments, making it one of the most deployed RTOS ever. In fact, there is a good chance that most people use products based on THREADX every day!

THREADX employs a priority-based, preemptive scheduling algorithm. Threads of the same priority execute cooperatively, with an optional per-thread time slice. THREADX supports most multithreading primitives, including event flags, semaphores, mutexes, message queues, and fixed and variable-length memory pools. The original version of THREADX also included a new technology called preemption-threshold, which helps reduce context-switching, improves responsiveness during critical sections, and helps prove a set of threads can be scheduled. To view the academic research, simply search for “preemption-threshold” in your browser.

THREADX is also popular in safety-critical applications and has been certified to the highest levels of the IEC 61508 standards, including IEC 61508 SIL 4, IEC 62304 Class C, ISO 26262 ASIL D, and EN 50128 SW-SIL 4. THREADX has also been certified.

THREADX was created by Bill Lamie and introduced commercially via Express Logic in March 1997. From the onset, THREADX was designed as a full-source code RTOS, written in C, which made it highly portable to any processor architecture with C compiler support.

The original version (3.0) featured a small, orthogonal proprietary API taking a noun-verb format. All THREADX APIs have a “tx_” prepended to isolate them in their namespace. For example, the THREADX API to send a message via a queue, is tx_queue_send. All APIs that suspend have an optional timeout parameter that specifies the maximum suspension time. Over the years, Express Logic evolved THREADX and added middleware such as FILEX, NETX DUO, USBX, and GUIX while always maintaining the original APIs.

Chronological list of noteworthy milestones:

Applications written for the original version of THREADX execute on the latest version of THREADX without change.

In April 2019, Microsoft acquired Express Logic and all of its IP, including THREADX and associated middleware. The THREADX and middleware products were renamed under the Azure RTOS umbrella and made publicly available on GitHub in 2020; however, they still required a license from Microsoft to be used in commercial applications. Most of the development effort during this period related to adding/improving cloud connectivity to Azure.

THREADX RTOS
Becomes
Open Source

In November of 2023, Microsoft announced the transition of Azure RTOS THREADX, FILEX, GUIX, GUIX STUDIO, NETX DUO, TRACES, and USBX to an open-source, free MIT license under the stewardship of the Eclipse Foundation. The new name for THREADX is “Eclipse ThreadX.”

Please visit Eclipse Foundation to learn more about open source RTOS.

In October 2024, RTOSX announced Bill Lamie's Industrial Grade alternatives to the Eclipse ThreadX, FileX, NetX Duo, and USBX packages. The new RTOSX KERNEL (alternative to ThreadX) includes some of the following features and benefits:

RTOSX continues to provide professional support for developers who want to stay with Eclipse ThreadX.