Overview

Keil RTX version 5 (RTX5) is a real-time operating system (RTOS) for Arm Cortex-M and Cortex-A processor-based devices that implements the CMSIS-RTOS2 API as its native interface.

Modern microcontroller applications must often serve several concurrent activities. Keil RTX5 manages the switching between the activities. Each activity gets a separate thread which executes a specific task and to simplify the program structure. Keil RTX5 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 RTX5 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 RTX5.

Features

Open-source

• Full-featured, free-to-use commercial-grade RTOS.
• Shipped under the permissive Apache 2.0 license.
• Configurable with no restrictions.
• Publicly developed on GitHub with full source code available.

Easy to use

• Reduced learning curve leading to faster product development.
• Provides configuration parameters for the kernel operation and the RTX objects.
• Configuration wizard annotations make parameter settings clear and intuitive in IDEs.

Safe and secure

• Keil RTX5 is PSA certified, integrating with the Platform Security Architecture API.
• The safety-certified variant FuSa RTX RTOS is available as part of the Arm Run-Time System for Functional Safety (FuSa RTS)

Flexible scheduling

Keil RTX5 offers various kernel scheduling options, allowing you to choose the best scheduling for your application.

Pre-emptive

• Each thread has a different priority and runs until a higher priority thread is ready to run.
• Commonly used in interactive systems where a device can be in standby or background mode until some input is sent to it.

Round-robin

• Each thread runs for a fixed period of CPU run-time (time slice).
• Data loggers or system monitors typically employ round-robin scheduling to sample all sensors or data-sources in turn with no prioritization.

Co-operative

Each thread runs until it is told to pass control to another thread or reaches a blocking OS call. Co-operative multi-tasking can be seen in applications that require a fixed order of execution.

Fully deterministic behavior

• Known behavior for time critical tasks.
• Events and interrupts are handled within a predefined time (deadline). Applications can rely on consistent and known process timings.

Low-power mode

• Tick-less operation mode for low-power devices.

Designed for embedded systems

• Requires minimal MCU resources with a memory footprint as small as 5 KB (ROM).
• Written for applications running on Arm Cortex-M-based MCUs.
• Quick run time.

Links

• Documentation
• Tutorial
• Examples
• Issues