Embedded, Real-time Operating Systems

The term ‘Embedded’ means ‘combined’. An embedded hardware device contains a single chip that stores hardware and software components of a computer, like the memory and the base operating system, together. Embedded software can be used for various purposes–right from powering hand-held mobile devices like pocket PCs to large-scale factory automation. To run these software, you need operating systems. Embedded operating systems are used in PDAs, high-end cellular phones, MP3 players, and Palmtop computers.

Embedded operating systems are available in three flavors: Windows, Linux and others. There are a few dozen embedded operating systems. We’ll take you through some of them.

Windows CE 3.0 There are no fewer than four versions of the Windows CE kernel designed for varying types of hardware. Windows CE includes 32-bit Windows technology and networking support amongst other features familiar to normal Windows users. A number of development tools are available for this platform. Database support is available through an SQL Server 2000, Windows CE Edition.
(www.microsoft.com/windows/

embedded/ce/default.asp)

Embedded Linux Linux is a powerful and full featured operating system, and its embedded version is no exception. Embedded Linux is free, just like its PC counterpart. Its source code is freely available, and allows developers of hardware devices to modify the core of embedded Linux to their preferences without having to go through long processes of licensing and paying for the operating system. In fact, many have predicted that the future of Linux is in the embedded world.
(www.linux.com).

Windows NT embedded Windows NT embedded is a little different from Windows CE. This embedded operating system is built on Windows technology and it excels in networking and communications, hence its name. 

Its price to hardware manufacturers is higher than most other embedded operating systems,
and therefore it is not a very popular alternative to Windows CE Edition. (www.microsoft.com/
windows/embedded/nt/default.asp) 

Palm OS Created by 3com, it is designed exclusively for PDAs. While the operating system supports only 8-bit (256) colors and networking is slower when compared to other embedded operating systems, the main difference between other operating systems and the Palm OS is that the Palm OS kernel is optimized for a specific hardware platform designed completely by Palm Computing. Other OEMs (such as IBM) have taken the core of the Palm OS and added new features to it, but they can’t change things such as the CPU, screen and controller chips.
(http://www.3com.com).

QNX Real-time Platform The ‘real-time platform’ of the QNX OS signifies something unique. It represents something present in both a real-time operating system and a platform OS. (For more on QNX, refer to New Life to Old Hardware, page 40, PCQuest March 2001) That fundamentally means that QNX has ‘priority driven multi-tasking’ and allows many tasks to be performed together (multi-tasking) at once without having one application running extremely slow or fast. QNX also has a very flexible kernel that consists of four parts (the process, file system, device and networking managers).
(www.qnx.com)

On-time RTOS 32-bit While other OSs are getting more and more resource-hungry by the day, this OS will even run on a x86 CPU with 16 kB of memory. It is fully compatible with Win NT and Win32 APIs. As with many of the OSs listed here, the full source code is freely available on the net, and therefore, fully modifiable to suit one’s needs. (www.on-time.com/)

Chorus OS The Chorus OS is the embedded OS offering from Sun Microsystems. It runs on a wide array of hardware, including ARM, MPC8xx, PowerPC, SPARC and the x86 in Real Mode. It supports dynamic allocating of memory for multitasking, and TCP/IP networking. After an initial period of free support, developers will have to pay for technical support, even on the company’ s official Internet BBS and FAQs. (www.java.sun.com)

ENEA OSE Systems The ENEA OS is designed with a ‘message-based’ architecture, so that developers could build real-time applications that require runtime maintenance, hot swapping of files, memory protection and error recovery. The source code of the OS also includes a debugger and sample programs among others.
(www.enea.com)

ROM-DOS This is an operating system that is both complex and flexible. It is not a free OS, but upgrades are free once the software has been registered or purchased. The OS also has specific utilities for different hardware. On the downside though, this RTOS supports only DOS and C compilers (no C++ or Java in the current
version)(www.datalight.com)

JBED The JBED embedded system is a promising RTOS–it supports any sort of a Java byte-code compiler (byte-code to native computer is included), and has earliest deadline first scheduling support with admission testing. The OS includes a debugger.
(www.esmertec.com)

RT Kernel RT Kernel is another real-time OS from On-time, which runs on x86 CPUs in real mode, and is designed for real-time multitasking under paradigm and DOS tools. The OS supports many debuggers including Turbo Debug, Codename, Paradigm and the Borland/MS integrated debuggers. The base price is $550, and upgrades are not free. The company provides unlimited and free technical support via FAQs and phone. (www.on-time.com/)

TinyBIOS It has a base price of $1995, and supports only x86 real and protected modes. No free technical support is offered by the manufacturer.
(www.pcengines.com/)

TurboTask The TurboTask OS has some great features. It can enable and disable device-interrupts when queues empty or fill. Most of the functions in the RTOS have support for finite or infinite delays. The software also does statistical allocation of resources to lower overhead.
(www.softools.com)

Nucleus Plus/Tasking It has all the features expected from RTOS these days like cCooperative multitasking and TCP/IP support. The source code and sample programs are also included. This OS supports only the CrossView Pro debugger.

But the main drawback of this OS is probably its price. At $12,500, it is definitely very expensive.
(www.tasking.com/)

Diamond The Diamond OS simplifies code development for high performance. During the design, the functional components are mapped to logical tasks, not dependent on hardware topology. In addition to these features, the OS also contains multi-processor support and sample programs, among numerous other minor features. The base price for this product is $3,500, and the
company offers free and unlimited tech support provided on BBS and FAQs. (www.zulu.threel.com/)

Dhruv Majumdar at PCQ Labs