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manual abstract
Enter LAN eXtensions for Instrumentation (LXI), Activities such as electronic functional test are often viewed as necessary evils that must provide a high return steve_stetler@agilent.com The automotive industry’s highly competitive nature puts intense pressure on electronic manufacturers to boost quality while lowering costs. on investment. an architecture for next- generation test systems based on proven, widely used standards such as Ethernet. Combined with the time-tested principles of providing just enough cooling, power, shielding and physical size to provide superb measurements in modular and traditional form factors, LXI’s appeal is bolstered by its availability in bench-top instruments, providing excellent performance at competitive prices. System designers who test automotive electronics can use LXI to maximize performance, minimize cost and plan for the future. There are at least nine good reasons to consider LXI for present and future test sys tems, as described in the April 2006 edition of LXI ConneXion magazine1: 1. Ease of use 2. Performance 3. Cost 4. Scalability 5. Longevity 6. Flexibility 7. Rack space 8. Distributed systems 1. Ease of use With the year-to-year changes in new car models, automotive electronics manufacturers must bring new products to market quickly. Rapid test system creation depends on getting instruments connected and systems running as soon as possible, which not only saves time but also enables manufacturers to focus on verifying the functionality of a module and its subassemblies. 9. IEEE-1588 synchronization 2 Many of these systems are created with VXI- or PXI- based hardware and controlled with either an embedded PC or standalone PC connected through an interface card and cable. LXI solves four key problems developers would typically face under these methods: • Interface: Rather than an MXI or GPIB interface, LXI uses Ethernet, eliminating the need to install an additional interface card in the PC. In addition, there are no proprietary cables or software. • PC configuration: Because a PXI cardcage is an extension of the PC backplane, the whole system must be rebooted every time a card is inserted or removed. With LXI, PCs do not require rebooting when connecting or disconnecting instruments. What’s more, some modular LXI instruments allow for “hot-docking” of cards while the power is on (Figure 1). • Drivers: When a PXI system reboots, the PC uses an instrument discovery process to identify newly connected devices, which usually requires operators to download and install device drivers. The LXI standard specifies the use of IVI-COM drivers, making it easier to work in a variety of development environments. And some LXI instruments can be programmed directly through Standard Commands for Programmable Instruments (SCPI) when greater functionality or performance is required. • User interface: With no front panel interface, using PC-based system software to diagnose problems in PXI and VXI devices can be difficult. With benchtop LXI instruments, the front panel interface makes it easy for developers to experiment with an instrument. While most modular LXI instruments lack a front panel, their built-in Web interface makes it possible to learn the capabilities by simply opening a Web browser on the connected PC. The browser function also makes it easier to see what’s happening with the equipment, simplifying system support and ensuring greater uptime. 2. Performance Automotive electronics testing includes everything from complex power train control modules requiring hundreds of tests, to simple airbag squib modules, to telematic/infotainment modules that may involve time-consuming transfers of huge data files. These tests often challenge GPIB’s maximum data rate of roughly 1 MB/s. With LAN, I/O transfer speed is becoming a non-issue with 1-Gbit/s connections becoming commonplace and 10-Gbit/s on the way.2 I/O performance should not be an issue for LXI devices in typical automotive applications that require both transactional programming and transfers of large data blocks such as waveforms captured by digitizers. In transactional programming, there is a well-understood issue around LAN latency. Instrumentation vendors are reducing the number of required communication cycles by preloading instructions to LXI devices. 3 3. Cost Minimizing the overall cost of test requires fast, reliable testing at as low a price as possible. Some trade publications have suggested that functional test adds no value: At this late stage, most manufacturers have inspected incoming parts, performed X-ray inspection and completed in-circuit test. While these steps do improve product quality, they do not eliminate the need for functional test because they cannot detect faults due to post-assembly product failures, design errors or inaccessible nodes. Automakers’ seemingly conflicting requirements compound matters. Instruments that deliver the necessary capabilities and performance at an attractive ...