Keil RTX

Keil RTX5 is a royalty-free, deterministic, full-featured real-time operating system implementing the CMSIS-RTOS API v2, a generic RTOS interface for Cortex-M processor-based devices. Features include periodical activation of timer functions, memory management, and message exchange between threads.

Modern microcontroller applications must often serve several concurrent activities. Keil RTX manages the switching between the activities. Each activity gets a separate thread which executes a specific task and to simplify the program structure. Keil RTX is scalable, and more threads can easily be added later. Threads have a priority allowing faster execution of time-critical parts of a user application.

Keil RTX offers services needed in many real-time applications, such as threads, timers, memory and object management, and message exchange. The following image shows the services of Keil RTX.

Keil RTX structure

Keil RTX Features

Included in MDK

Keil RTX5 is shipped free with Keil MDK. It is fully configurable and publicly developed on Github under the permissive Apache 2.0 license.  

Easy to Use

Keil RTX5 is well supported within the µVision IDE/Debugger, which features RTX-aware tools that enable you to quickly debug your real-time applications so product development is faster and learning time is reduced.

Built for Embedded Systems

Its small memory footprint (down to 5KB in ROM) and high speed make Keil RTX5 ideal for embedded systems. Select from multiple kernel scheduling options to find the best one for your application.

Deterministic Behavior

Keil RTX5 delivers fully deterministic behavior, which means that events and interrupts are handled within a predefined timeframe or deadline. Your application can rely on consistent and known process timings. 


There are no run-time royalty payments or other hidden charges. Ship your RTX based products without further fees or recurring costs.

Functional Safety

A qualified version of Keil RTX is available for functional safety applications.

RTOS for Middleware for Cortex-M

Format: online training
Duration: 2 days, from 9:00 a.m. to 1 p.m.
Language of instruction: German (presentation slides in English)
Costs: 650.00 EUR (early bird discount 100 EUR)