Integrating PXI and VME in Hybrid Multiplatform Systems
PrintThe architecture of an embedded system depends on software preferences, reliability considerations, and future requirements. With the current pace of innovation, investing in state-of-the-art technology is necessary to keep up with a highly competitive environment. Two decades ago, considering the limited options available and lack of commercial off-the-shelf (COTS) technology, engineers invested in platforms such as VME to meet their application needs with custom hardware and software. However, today VME has become a legacy platform because of the lack of new technology development and investment in the platform.
Motorola introduced the VME bus in 1981 at a time when aggregate bandwidths exceeded 1 MB/s. Within a short period of time, the VME bus became dominant in the backplane industry and was widely accepted in the embedded computer boards market. A good percentage of these applications were in the military and aerospace industries, which used the VME backplane to implement custom protocols. Today, two decades after these systems were implemented, engineers face a myriad of issues such as maintenance, support, obsolescence, and a lack of scalability that may be required for a new series of tests. Engineers could spend most of their time working to find ways to improve performance and update their systems to work with current technologies.
Thus, system designers face a dilemma – whether to move to a new state-of-the-art COTS platform or reverse engineer VME systems to find ways to improve performance and implement current technologies. In most cases, it is not economical to move to an entirely new platform, nor is it strategic to invest resources in reverse engineering just to gain improved performance. In these situations, one efficient solution is to build a hybrid system using COTS technology, which increases system performance while preserving investment.
Hybrid Multiplatform Systems
If you have an existing investment in the VME bus, you may not be able to switch to a newer platform. Rather, you can use hybrid multiplatform systems to extend the life of your system, maximize your investment in existing equipment, and take advantage of newer technologies. Hybrid systems combine components from multiple platforms, such as VME, VXI, PXI, GPIB, USB, and Ethernet, into one system. Using hybrid systems, you can integrate components into your existing system as needed without a complete redesign.
Figure 1. Hybrid multiplatform systems combine components from multiple platforms into one system.
Using a hybrid system architecture, you can integrate instruments from different buses into the device I/O layer to create the system that best fits your needs. For example, you can integrate your VME system and specialized or custom instruments with the latest PXI technologies for high-performance, low-cost instruments. You can choose from a broad range of controllers to connect the various buses in the computing layer, such as the VME-PXI MXI-2 controller, which connects a VME system to a PXI system.
PXI takes advantage of COTS technology and is based on standard PC technologies – such as the PCI bus; standard CPUs; peripherals such as USB, GPIB, Ethernet/LAN, serial, and parallel; and standard Windows software architectures. Because PXI is based on standard PC technologies, it incorporates state-of-the-art technologies such as PCI Express, field-programmable gate arrays (FPGAs), real-time operating systems (RTOSs), and multicore technology, making it a high-performance, cost-effective platform to integrate with legacy VME systems.
Figure 2. The National Instruments LabVIEW FPGA Module offers the best combination of hardware customization with COTS PXI modules.
One of the biggest challenges in trying to maintain an existing VME system is the long-term supportability of custom hardware. Boards with specialized functionality may not be available on the commercial market, and trying to find and replace legacy components is not easy. With hybrid architectures, existing VME systems can interface with customizable FPGA-based instrumentation and continue to take advantage of commercially available hardware.
Several PXI modules offer user-programmable FPGA chips that you can graphically configure using the NI LabVIEW FPGA Module to implement custom functionality without prior hardware design expertise. One example is interfacing to a legacy bus based on a digital protocol such as High-Level Data Link Control (HDLC). Many legacy communication protocols no longer have COTS interface hardware, and system designers are forced to develop custom hardware. You can reconfigure FPGA-based PXI modules to implement almost any digital protocol – legacy, standard, proprietary, or confidential. Typically, reusable code modules are referred to as “IP cores” for intellectual property. The LabVIEW FPGA Module offers hundreds of example programs and IP cores that either ship with the product or are available for download on ni.com. This collection of reusable IP and high-performance PXI hardware can add new capabilities to your existing VME system by combining the best of custom-made and COTS systems.
In addition to custom FPGA capabilities, PXI offers a wide range of measurement, automation, and control I/O modules from DC to RF that you can use to complement your existing VME systems.
Conclusion
To successfully compete in today’s environment, you must use the latest technologies to get the best possible performance, while preserving existing investments. The most efficient solution is to build hybrid systems using COTS technology. By combining PXI and VME hardware with LabVIEW software, you can achieve higher performance at a reasonable cost increase. This approach also improves your ability to design and support custom hardware to implement custom protocols using FPGA-based instrumentation.
Murali Ravindran
PXI Controllers Product Manager
Vineet Aggarwal
Data Acquisition Product Manager
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