Real-time USB device software stack designed for embedded systems that allows the creation of products that interoperate with standard USB devices.



Key Features

Thanks to a hardware abstraction layer, you can easily port Cs/USB software to any new USB device by simply modifying existing hardware access routines.

Support for High Speed (480 Mbit/s) and Full Speed (12 Mbit/s) devices

Compliant with USB 2.0 specification

Easy-to-use API

Extensive test cases and test harness to verify stack integration

Support for composite (multifunction) devices

Support for multiple USB device configurations

Power saving functionalities such as device suspend and resume

Support for Audio, CDC-ACM, CDC-EEM, HID, MSC, PHDC, and Vendor classes

Support from Microsoft OS Descriptors for USB devices (which simplifies installation of vendor-specific drivers on Windows OS)


Class Support

USB Device Classes

Class Example USB Devices
  • Support audio devices such as speakers, microphones, headset, etc.
  • Extended audio functions (such as adaptive audio correction) and controls (volume, mute, treble, bass, etc.)
Communications Device Class Abstract Control Model (CDC-ACM)
  • Emulation of a virtual serial port on the host PC
  • The host PC can communicate with the device using a serial terminal or native serial communication APIs
Communications Device Class Ethernet Emulation Model (CDC-EEM)
  • Ethernet networking over USB
  • The Cs/NET stack is used for network communication and any of its applications can be used
Human Interface Device Class (HID)
  • Support for devices such as mice and keyboards
Mass Storage Class (MSC)
  • Support for storage media from the host PC
  • Offers advanced features such as interoperability with Cs/FS file system module
Personal Healthcare Device Class (PHDC)**
  • Allows to build USB devices that are meant to be used to monitor and improve personal healthcare
  • USB Device Class Definition for Personal Healthcare Devices, release 1.0, Nov. 8 2007
Vendor Class
  • The vendor class allows you to create any device that cannot fall into a standard class for which a standard has been set by the USB implementers forum. It allows you to perform raw bulk and interrupt communications with the host. Cs/USBD offers a framework to help create host applications (Windows OS only) that communicate with these devices.

* Available for devices using the Synopsys_OTG_HS driver.

** Available for devices using Cs/OS2


Driver Support

USB Device Controllers

Driver Examples of Platform
  • Atmel AVR UC3 C-Series (AT32UC3C)
  • Atmel AVR UC3 A0-Series (AT32UC3A0x)
  • Atmel AVR UC3 A1-Series (AT32UC3A1x)
  • Atmel AVR UC3 B-Series (AT32UC3B)


  • Atmel SAM3U
  • Atmel SAM9R (e.g. SAM9RL64)
  • Atmel SAM9M (e.g. SAM9M10)
  • Atmel SAM9G (e.g. SAM9G45)
  • NXP Kinetis K series
  • NXP LPC17xx (e.g. LPC1768)
  • NXP LPC214x (e.g. LPC2148)
  • NXP LPC23xx (e.g. LPC2378)
  • NXP LPC24xx (e.g. LPC2468, LPC2478)
  • NXP LPC29xx
  • NXP LPC318x
  • NXP LPC313x (e.g. LPC3131)
  • NXP LPC185x (e.g. LPC1857)
  • NXP LPC183x
  • NXP LPC182x
  • NXP LPC435x (e.g. LPC4350)
  • NXP LPC433x
  • NXP LPC432x
  • Xilinx Zynq
  • NXP i.MX
  • NXP Kinetis K70
  • Renesas RZ/A series (RZ/A1)
  • Renesas RX64M
  • Renesas RX600 series (RX62N, RX63N, RX630)
  • Renesas RX100 series (RX111)
  • Renesas V850E2/Jx4-L series
  • ST STM32 F1 series (e.g. STM32F105, ST STM32F107)
  • ST STM32 F2 series (e.g. STM32F207, ST STM32F217)
  • ST STM32 F4 series (e.g. STM32F407, ST STM32F417)
  • ST STM32F103xx (e.g. STM32F103ZE)
  • ST STM32F102xx
  • ST STM32L1xx (e.g. STM32L152)
  • ST STR9
  • Texas Instruments RM48 series
  • Texas Instruments Stellaris LM4F series
  • Texas Instruments Tiva C-series

If you don’t see the driver you are looking for please contact us. We can give you the latest information on drivers we have available.


Stack Compliance

USB Command Verifier (USBCV) is used to validate the compliance of the stack with the USB Specification. USBCV is the official compliance test tool that evaluates High, Full, and Low-speed USB devices for conformance. This tool is provided by the USB Implementers Forum (USB-IF).

USBCV offers a test suite to validate the compliance of a device with Chapter 9 of the USB specification Revision 2.0 (enumeration process). It also offers a test suite for several classes.

The following table lists the different layers of Cs/USBD and the USBCV test suite used to validate the implementation.


Layer USBCV Test Suite
Core Chapter 9 tests
Human Interface Device class HID tests
Mass Storage Class MSC tests
Device Controller Driver Chapter 9, HID, MSC, and PHDC tests


Commercial License

Click here for more details


Technical Support

Technical Support Plan

Technical support services for any of the Cs/ software is readily available to all customers currently using or interested in the Cs/ family of RTOS components.

If you are currently without technical support for the Cs/OS software don’t go at it alone. Please contact us to learn how our Cs/OS product experts, with years of embedded software experience, can save you valuable engineering time and money.

Click here for more details


Consulting Services

Specialized Engineering Services

Do you need specialized assistance with your Cesium-based embedded project? Do you need real-time embedded software expertise for your mission critical application? For these or any other embedded software projects, help is available via our Consulting Services that are tailored to your unique needs. Please contact us with your requirements to learn how we can quickly deliver our expertise to your team.

Click here for more details



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.