Try Cesium RTOS Free for 30 Days

At the heart of cutting-edge embedded systems lies Cesium RTOS. Engineered for precision and performance, Cesium RTOS is your gateway to unleashing the full potential of your projects. Designed by the makers of the popular Micrium µC/OS, it embodies our commitment to delivering high-quality, dependable, and efficient real-time operating systems.

Efficient Processing: Cesium RTOS optimizes CPU cycles for peak performance. Its streamlined design enhances application smoothness, responsiveness, and reliability, cutting the unnecessary overhead found in competing systems.

Reliable: Dependability is critical for embedded systems, and Cesium RTOS stands up to the challenge. Designed for applications where failure is not an option, it keeps your projects running securely.

Ease of Development: Cesium RTOS simplifies embedded system development. With a straightforward API and clear documentation, it makes the development process more efficient.

Scalable: Cesium RTOS fits projects of any size, from small gadgets to extensive industrial systems. Its flexible architecture adapts easily, ensuring consistent performance on diverse hardware.

Direct Support from the Developers: With Cesium RTOS, you're not just acquiring a robust operating system; you're also getting direct access to dedicated support from the very experts who developed the software. Forget navigating through forums or community posts for answers. Our direct line of support ensures you receive accurate, timely help directly from the source, streamlining your development process and helping you overcome challenges swiftly and efficiently.


Cesium trial 1


What's Included

Both Real-Time Kernels

Cs OS2 logo 

Cs OS3 logo

All communication stacks

Cs NET logo

Cs USBD logo

Cs USBD logo

The embedded FAT File System

Cs FS logo

Comprehensive documentation in PDF form

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Out-of-the-box examples for popular STMicroelectronics development kits


Visual Studio simulator for a hardware-free alternative

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Getting Started

Fill out the form below

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Read and acknowledge the Terms and Conditions

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You will receive a download link in your email

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Download the trial package

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Follow the readme instructions

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Terms and Conditions

This Evaluation License governs your use of the Licensed Products. If you do not agree to the terms of the Evaluation License, you are not granted any rights whatsoever in the Licensed Products and you may not access or use the Licensed Products in any manner. Your continued access to or use of the Licensed Products may also be subject to your acceptance of updates to this Evaluation License, as applicable.

You are entitled to evaluate the Licensed Products for 30 days only.

At or before the end of the 30-day evaluation period you agree to either purchase license(s) for the Licensed Products, or you must discontinue the use of all Licensed Products, remove all software from all computers, including all copies, and agree that you will not use the Licensed Products in any product (internal or commercial) after the expiration of the 30-day evaluation period. You may not keep any personal copies of the Licensed Products for any reason.

The Licensed Products are available free of charge during the 30-day evaluation period. However, if you use the Licensed Products in any way after the 30-day evaluation period has elapsed and you have not purchased a license, then you agree to pay the Licensor the appropriate license fee based on your actual use of the Cesium RTOS Software, which shall not be less than $8000.00 USD. Such amount shall be due and payable upon demand.

The Licensed Products are for your evaluation only and cannot be used in any internal company or commercial products without prior written permission of the Licensor. You may not embed the Cesium RTOS Software in any of your end products. The Licensed Products are provided only to you, and you may not sell, distribute, or disseminate in any way the Licensed Products in any manner or any form, including source code, object code, or executable code. You may not copy, edit, change, enhance, re-format, reverse engineer, or otherwise modify the Licensed Products. To the extent not licensed to you, all rights to the Licensed Products, in trade secret, copyright, patent, or otherwise, and all improvements and modifications thereto, shall at all times remain with the Licensor.

The Licensor of the Cesium RTOS Software is Weston Embedded Solutions, located at 2200 N. Commerce Parkway, Suite 200 Weston, FL 33326.

As used in this Evaluation License, “Licensed Products” means the Cesium RTOS Software and related materials, including documentation, media, manuals, specifications, instructions and printed materials, and any copies or portions thereof, furnished by Licensor to you for use with the Cesium RTOS Software. “Cesium RTOS Software” includes all software code and proprietary information in the Licensed Products, including but not limited to source code, object code, and executable code.

You affirm that your company has authorized the evaluation of the Licensed Products and intends to consider them for use in your company’s end products. Additionally, budgeting and funding for the purchase of the Licensed Products, consistent with the quotation(s) provided, has been pre-approved by your company should you decide to purchase the Licensed Products.

THE CESIUM RTOS SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND and no other warranties, express, implied, statutory, or arising from the course of performance, course of dealing, usage, or trade, are given by Licensor, and all other warranties, including but not limited to express, implied or statutory, are expressly disclaimed.

Licensor neither provides nor assumes any warranty concerning the Licensed Products provided; does not guarantee the accuracy, adequacy, or completeness of any software provided, and is not responsible for any errors or omissions or the results obtained from the use of the software. Your sole and exclusive remedy for any breach of the terms of this Evaluation License or any dissatisfaction with the Licensed Products for any reason shall be discontinuation of your use of the Licensed Products and a return of the Licensed Products to the Licensor.

Licensor has no liability for any damages suffered by you by reason of any act or omission of Licensor or any of its employees, contractor, directors, agencies or affiliates, or arising out of or in connection with the Licensed Products, Licensor’s performance under the Evaluation License or any use of the documentation, media, manuals, specifications, instructions or printed materials accompanying the Cesium RTOS Software, including without limitation any loss of use, lost revenues, lost business opportunities, lost profits, costs associated with downtime and any similar and dissimilar losses, costs or damages. In no event shall the Licensor be liable for consequential, incidental, special, or punitive losses, damages, or expenses (including lost profits or savings), even if the Licensor has been advised of their possible existence. These allocations of risk are reflected in the terms you have negotiated with the Licensor, who would not have been able to provide you with the Licensed Products without this limitation. The limitation of liability shall survive the termination of this Evaluation License.

You understand and agree that the Licensed Products constitute confidential and proprietary information of the Licensor and agree to maintain the Licensed Products in confidence to the same extent that you maintain such confidentiality to protect your proprietary information, but not less than a reasonable level of care. You are not authorized to duplicate the Cesium RTOS Software (other than as necessary to install and operate it), to disclose the Cesium RTOS Software to persons outside of your company, or to use the Cesium RTOS Software for any purpose other than evaluation. All confidentiality obligations shall remain in effect for five (5) years from the date of termination of this Evaluation License.

You may not assign this Evaluation License, in whole or in part, without the Licensor’s prior written consent. Any attempted assignment without the Licensor's prior written consent shall be null and void. The waiver of any default or breach of this Evaluation License does not constitute a waiver of any other or subsequent default or breach. This Evaluation License is governed by the laws of the state of Florida, without regard for its conflicts of laws provisions or the 1980 United Nations Convention on Contracts for International Sale of Goods. All disputes concerning this Evaluation License shall be resolved by binding arbitration in Broward County, Florida before a single arbitrator. The arbitration shall be administered by JAMS under JAMS’ Streamlined Arbitration Rules and Procedures. The arbitration award shall include an award of attorneys’ fees to the prevailing party. Judgment on the award may be entered in any court having jurisdiction. This clause shall not preclude parties from seeking provisional remedies in aid of arbitration from a court of appropriate jurisdiction.

THIS LICENSE EXPIRES 30 DAYS AFTER THE DATE YOU RECEIVE THE SOFTWARE. If you wish to extend the term of this Evaluation License, you must contact the Licensor directly at

By clicking "SUBMIT" below, you agree to the terms and conditions of this Evaluation License and represent that you are authorized to enter into this agreement on behalf of your company.


Cesium software includes comprehensive documentation, full source code, powerful debugging features, and support for a huge range of CPU architectures.


Cesium software offers unprecedented ease-of-use, a small memory footprint, remarkable energy efficiency, and all with a full suite of protocol stacks.


Engineers across the world building industrial controls, medical devices, and aerospace systems know they can rely on Cesium software for the foundation of exceptional products.