Test Connections - May 2011

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FPGA-Based Instrumentation: Performance and Flexibility for Test Solutions

In the automatic test equipment (ATE) sector, technology advances and constantly increasing demands for greater efficiencies, more capabilities and quicker time to market contribute to a common goal for test and measurement systems: Develop performance test systems with specialized needs faster and with lower life-cycle costs. In a May 2010 Test & Measurement World article, Richard Quinnell, contributing technical editor, states that the advent of PXI Express has allowed faster data handling and that developers increasingly turn to field-programmable gate array (FPGA) technology for handling these data. FPGA-based
Geotest GX3500 FPGA Board
designs create an environment that supports not only more efficient data handling, but also offers greater flexibility than ever before when designing a customized interface or instrument. However, the FPGAs in PXI modules have been nearly inaccessible to system developers and end users. Vendors provide the module upgrades and enhancements, and users are not able to easily incorporate their own ideas. However, during the last two to three years, the  introduction of user-configurable FPGA modules for PXI has changed that. Now, FPGA performance and configurability benefits are available to both system developers and end users, adding a new range of design possibilities for PXI systems.
Presenting user-configurable FPGAs At the recent Electrotest show in the U.K., Victor Femandes, European sales manager at Geotest, gave a presentation about user-configurable FPGA modules for PXI systems. In it, he emphasized that the use of FPGA-based test instruments has grown exponentially over the last couple of years. He cites the following benefits and advantages as big factors in this rapid growth.
  • High reliability — With an FPGA-based design, the instrument’s functionality is insulated from the test system’s operating system (OS), so if your application or OS
Related Resources For more information about working with user-configurable FPGA test systems, take a look at these resources on the Geotest website. Guidelines for designing an FPGA board
An FPGA-based solution for testing legacy video displays
Controlling a GX3500 FPGAusing reads and writes
      crashes, the hardware will continue to operate.
  • Low latency — Without an instrument control bus between the instrument logic and the measurement, decision-making and signal processing can occur as soon as a sample has been acquired.

  • Reconfigurability — FPGAs aren’t only programmable; they are also reprogrammable, which means the user has the flexibility to reconfigure the device to accommodate application or design changes.

  • High performance — FPGAs are fast and parallel. Computation that can't be done with a microprocessor may be possible with an FPGA.

  • True parallelism — A single FPGA can often implement the same measurement or signal processing algorithm in parallel, providing a high-bandwidth signal processing engine.
The presentation outlined two types of  FPGA products: software flexible/hardware fixed and software/hardware flexible. Software flexible/hardware fixed products The use of FPGAs on a commercial off-the-shelf (COTS) board allows users to
  • Install new firmware to gain new features.
  • Create unique functions for customers.
  • Upgrade and modify module functions in the field, which helps expand a product’s capabilities and life cycle.
Software and hardware flexible products There are three main types of products associated with  this category:
  • cPCI Digital — These products are low cost and are typically targeted for embedded/system solutions. They do not  take advantage of PXI backplane resources (e.g., triggers, clock) and are typically not effective for test and measurement applications.

  • PXI Analog — These products may appear to be good, multifunction solutions, but in reality they offer  expensive, low-performance, mixed-signal solutions.

  • PXI Digital —These products are focused on providing custom solutions for high-performance, complex test applications.
Femandes’ presentation highlights these PXI Digital products (FPGA Flex DIO) and presents a compelling case for why these types of products are the best choice for addressing complex, custom  digital test applications. FPGA test system solutions from GeotestGeotest is at the forefront of the move to user-configurable FPGA modules for PXI test systems. The company offers software and hardware components to help harness the speed and flexibility of FPGA test solutions. Its offerings include: GX3500 Digital I/O FLEX FPGA PXI Card — A user-configurable 3U FPGA PXI card that has 160 digital I/O signals for specific application needs. The card employs the Altera Cyclone III FPGA and features more than 55,000 logic elements and 2.34 MB of memory. The 3U PXI FPGA card GX3500 can also accept an expansion card assembly that can customize the interface to the UUT, eliminating the need for additional external boards that can be difficult to integrate into a test system. The GX3500 is supplied with drivers and a virtual panel making it easy to control the card as well as debug and integrate or load the compiled FPGA firmware into the GX3500. GX3500 Expansion Boards — Geotest offers a family of logic interface expansion modules for its GX3500 FlexDIO PXI FPGA product. The GX3501, GX3509, GX3510, and GX3540 provide multi-channel interfaces for LVTTL, differential TTL, mLVDS and ECL logic families respectively. The GX3501, GX3509 and GX3510 feature 80 I/O channels with each channel independently configurable as an input or output. The GX3540 features 20 input and 20 output ECL channels with a selectable termination to -2V or -5.2V.
Geotest depends on the success of its customers' applications. If you have specialized instrumentation needs, an FGPA-based solution may be the solution. Click here to see how Geotest can customize a testing solution for you.