Special FEATURE By Heinrich Munz Heinrich Munz of KUKA Roboter discusses in this article how to bring Microsoft Windows CE and WindowsXP together on the same PC. He discusses system and application requirements, communications, loading, and activation by interrupts and lists the technical and commercial features of each.
Microsoft Windows XP Microsoft s Windows XP includes a graphical user interface that is widely used for IBM PCs. Due to the absence of real-time ability, however, Windows XP has not been suitable for all industrial applications. On the other hand, Microsoft Windows has the advantage of having both widespread applications and broad user acceptance. Moreover, many low-priced user programs for Windows are available. Developers have recently created a way to make Windows useful for industrial real-time applications, eliminating the disadvantages of Windows without giving up its advantages. Microsoft Windows CE Windows CE (the embedded Windows) is a widespread Real-Time Operating System (RTOS). Several versions of Windows CE are available for different processor architectures (ARM, MIPS, Intel 80x86, and others). Windows CE normally runs standalone on a single processor with exclusive use of RAM, ROM, I/O hardware, and other resources. CeWin brings Windows CE and Windows XP together on one PC The CeWin product family combines the Windows CE and XP operating systems, so they can run concurrently on the same PC, and the user can get the best of both worlds. To make this possible, Microsoft has developed a software-only, real-time extension technology for Windows XP, CeWin. The new technology guarantees deterministic response on interrupts that are targeted at Windows CE. Any PCI or ISA PC plug-in board controlled by Windows CE can generate these interrupts, and interrupts aimed at Windows CE always receive a higher priority than those targeting Windows XP. As long as at least one Windows CE task is active, the processor s execution time is available exclusively for Windows CE. Windows XP will be reactivated only if all Windows CE tasks have given up their execution time, and Windows CE has entered an idle mode. Windows XP may be said to run as the idle mode of Windows CE. The Windows CE idle mode controls the reactivation of Windows. This makes it possible for the programmer to control processor sharing between the two operating systems according to the application requirements. There are two members within the CeWin product family: CeWin PE (Professional Edition) and CeWin LE (Light Edition). While CeWin PE has the full functionality of the original Windows CE, CeWin LE as a low-cost entry product has some limitations: Pre-configured images have several fixed sizes that cannot be modified. Additional OS features cannot be included. Development environment: Embedded Visual Studio and Visual Studio.NET Platform Builder cannot be used. Only one user process is supported. CeWin LE does support Transmission Control Protocol/Internet Protocol (TCP/IP) communication between Windows XP and Windows CE but with no routing (IP Forwarding) support. However, both versions do support: Access of the local Windows XP hard disk (i.e., to load the user application) Win32 subset API, Visual C++ Windows CE console access using Telnet The CeWin product license from KUKA Roboter only consists of the coupling mechanisms to have both operating systems concurrently on the same PC. However, it does not include the two required original Microsoft licenses for Windows XP and Windows CE. Those have to be procured at the official Microsoft distributors. CeWin installation has to follow installation of the two original software products. Communication between Windows CE and Windows XP The TCP/IP protocol is used for communication between Windows CE and Windows XP using shared memory areas. For this purpose, two corresponding network drivers have been developed for the Windows XP and Windows CE sides. Both systems can exchange data over the commonly accessible shared memory area as they would via an Ethernet line. Using the Windows XP built-in IP-Forwarding feature, Windows CE can access other systems that are connected to the Windows XP TCP/IP network. This communication method offers the advantage of allowing the two systems to be torn apart and connected by a real Ethernet line without changing one of the applications. This approach makes sense if the real-time target system is not only PC-based but also an embedded system like a standalone controller without Windows XP functionality. Users can install a more direct TCP/IP connection to systems outside the PC using additional Ethernet hardware. An Ethernet board, which is supported by a standard Windows CE driver, can be plugged into the PC. Usually, this requires using an Ethernet board that is in addition to the Ethernet board used by Windows. CeWin controls this additional Ethernet board directly. Using the Windows XP built-in IP-Forwarding feature, Windows CE can access other systems that are connected to the Windows XP TCP/IP network. Using the standard TCP/IP protocol, any additional Windows CE products, for example, development systems such as Platform Builder or Kernel Tracker, can be used together with CeWin. As Windows CE and Windows XP run on the same processor, no special host is required for development. For the runtime system, TCP/IP sockets, etc., can be used for proprietary communication protocols between Windows XP and Windows CE programs. Alternatively, standard mechanisms such
as DCOM or SOAP may be used for communication. When considering the application features of both Windows CE and Windows XP, there is no difference between running under CeWin on the same PC (Figure 1) or running on two different systems as usual (Figure 2). Host and target systems are identical. Loading and starting CeWin After Windows XP is up and running, a user can start CeWin by uploading the Windows CE image file (see Figure 3) with a little loader tool, which is a Win32 application, easily integrated into a userwritten Windows XP application. This application communicates with the CeWin interface driver loaded during the Windows XP boot sequence. Initially, the loader calls the driver to allocate memory that Windows CE later uses for code and data. The allocated memory is guaranteed to be fixed (not swapped to disk), and the code running in this memory has the highest privilege level (Ring 0). The loader s next step is reading the Windows CE image from disk, and copying it to the allocated memory on behalf of the driver. After the code and data are relocated to the loading address, calling the init function of Windows CE starts Windows CE. As soon as all initialization Figure 2 Figure 1 Figure 3
tasks are idle, the init function returns, and the loader terminates. From now on, Windows CE will only be activated by real-time interrupts (see Figure 4) followed by task scheduling. Activation of CeWin by interrupts The interrupts for Windows CE as well as for Windows come directly from the PC s Programmable Interrupt Controller (PIC). However, the CeWin real-time extension technology ensures that the interrupts enabled for Windows CE always have higher priority than everything in Windows (including Windows interrupts). These interrupts will interrupt Windows XP or CeWin tasks within a few microseconds and call the corresponding Windows CE Interrupt Service Routine (ISR). After returning from the ISR, but before returning to Windows, the system checks if there are any Windows CE tasks ready to run. If this is the case (one or more tasks have been activated within the ISR), the system will not return to Windows, but it will activate the corresponding Windows CE task first. As mentioned earlier, those tasks keep running until all of them are suspended again. The system then enters the idle mode of Windows CE, which will lead to a return to Windows XP. Windows XP will only be reactivated if all Windows CE tasks are idle. The Windows CE idle mode controls the reactivation of Windows, enabling processor sharing between Windows CE and Windows XP. See Figure 5 for a state diagram of CeWin. Exception handling of Windows CE Whenever Windows CE is activated via the ISRs, a new exception table is loaded by only one assembler instruction. Therefore, the exception handling for page faults, debugging, and so on is exactly the same as if Windows CE were running standalone. Before falling back to Windows XP, the exception table is reloaded. The arithmetic coprocessor can be used within CeWin without any restrictions. It is possible that the interrupted Target with Windows CE Windows XP has the coprocessor currently in use, so the state of the arithmetic coprocessor is saved whenever Windows CE needs it and is restored before returning to Windows XP. The Windows CE idle mode controls the reactivation of Windows, enabling processor sharing between Windows CE and Windows XP. TCP/IP on PC wit Figure 4 Figure 5
Key attributes are: Real-time extender for Windows XP using Windows CE PC-based automation (PLC, motion control) Real-time measurements and controls PC and HMI add-on for existing Windows CE applications Windows CE target simulation with real-time behavior and hardware access The technical features are: Full usage of the RTOS Windows CE concurrently to Windows XP Multitasking, intertask communication, Win32 API TCP/IP stack, ISAPI, ASP, SOAP, etc. Optional products Runtime environment for Visual C, Visual C++, Visual C#, Visual Basic, etc. Software-only solution, no additional hardware necessary Use of the well known Microsoft development tools for Windows XP as well as for RTOS development Graphical real-time analysis tools (Kernel Tracker, etc.) High resolution real-time timer, granularity 0.8 µs Hardware access to ISA and PCI plugin boards Use of the original Win32 API for Windows CE All additional features of Windows CE Communication between Windows XP and Windows CE via shared memory TCP/IP; use of DCOM or SOAP possible Access of the Windows hard disk (using a directory share) The commercial features include: No need for additional intelligent coprocessor board or separate control Reduction of hardware costs Fewer hardware components: reduction of failures More compact controls possible Small learning curve Known tools (Visual Studio, Visual Basic, etc.) Win32 API Reuse of existing Windows CE software and know-how is possible Two scaled versions available Low cost entry product CeWin LE (Light Edition) Full version CeWin PE (Professional Edition) How to work with it Use Microsoft tools as the Integrated Development Environment (IDE) to develop and debug real-time applications. In addition, Wizards are available to generate applications. Visual Studio enables development, test, and debugging of the real target, with no simulation, on the same PC. A shared memory TCP/IP facilitates communication between Windows XP and Windows CE. A Win32 application can be built into a user application (DLL) enabling start and stop of the RTOS after Windows is up and running. Heinrich Munz cofounded LP Elektronik in 1985, focusing on software and hardware contract development. Heinrich was instrumental in LP s development of plug-in boards for PCs to couple RTOSs like OS-9 and VxWorks with DOS, and later Windows. Having the goal of bringing together the PC-based office world with its powerful tools and the poorly equipped industrial automation world led to LP s development of a Real Time Extender Technology in 1993 for the 16-bit Windows OSs and Windows NT family. In 1994, KUKA Roboter acquired LP Elektronik, which in 2002 was renamed KUKA Controls. Today Heinrich works with KUKA as a strategic product manager. KUKA Roboter GmbH, Augsburg, is an IWKA Group company and is a worldwide leading manufacturer of PC-based industrial robots. The company s core competencies are the development, production, and sale of industrial robots, controllers, software, and linear units. In 2002, company sales were C250 million Euro. For more information on KUKA Roboter GmbH, call Jürgen Schulze, PR Manager, at 0821-4533 3473 or visit the Web site at www.kuka-roboter.de/english. KUKA Roboter GmbH Zügspitzstrasse 140 D-86165 Augsburg Postfach 431364 D-86073 Augsburg Tel.: +49-821-797-4000 Fax: +49-821-797-1616 E-mail: info@kuka-roboter.de Web site: www.kuka-roboter.de/english Information contained herein supersedes previously published specifications and is subject to change without notice.