LXI

LAN eXtensions for Instrumentation (LXI) is a standard developed by the LXI Consortium, it was officially released in September 2005 by Agilent Technologies and VXI Technology. The LXI Consortium now has over 50 member companies, whose strategic members are (in alphabetical order) Agilent Technologies, Keithley Instruments, Pickering Interfaces, Rohde & Schwarz and VXI Technology. Further significant LXI Consortium members include: The Department of Defense, Aeroflex, BAE Systems, Anritsu, Geotest, Lambda, [http://www.bksv.com Bruel and Kjaer] , EADS North America Test and Services (formerly Racal Instruments), LeCroy, The MathWorks, National Instruments, ADLink, California Instruments, Data Translation, JDS Uniphase, Kepco, Teradyne, Yokogawa, Xantrex and ZTEC Instruments.

The first fully comformant LXI devices were approved in Dec 2005 from Agilent and Pickering, there has since been rapid growth with 502 approved LXI instruments as of April 2008 [http://www.lxistandard.org/applications/products/] . The LXI Consortium claims that the sales of LXI equipped instruments has exceeded annual sales of $200m within 2 years of launch, much faster ramp up than any previous standard [http://www.tmworld.com/article/CA6478136.html] and is expected to replace the >$5bn GPIB market as well as much of the VXI market [http://www.lxistandard.org/press/papers/presentationOverview/LXI_Bkgrndr_April_2006.pdf] .

LXI Overview

LXI is the LAN-based successor to GPIB [http://www.tmworld.com/article/CA6488095.html] . The LXI standard defines devices using open-standard LAN (Ethernet) for system interdevice communication. The standard will evolve to take advantage of current and future LAN capabilities. It provides capabilities that go well beyond the capability of legacy test and measurement connectivity solutions. LXI provides users with solutions that are denser, smaller, faster and cheaper than legacy solutions [http://www.tmworld.com/article/CA6488095.html] . LXI's choice of Ethernet is based on it being low cost, full support on all computer platforms, peer-to-peer communications capability, reliability (TCP/IP is a robust protocol), voltage isolation, and the expectation of a long term secure future roadmap whilst maintaining full backward compatibility with all implementations.

The LXI Standard has three key functional attributes:
* A standardized LAN interface that provides a framework for web based interfacing and programmatic control. The LAN interface can include wireless connectivity as well as physically connected interfaces. The interface supports peer to peer operation as well as master slave operation.
* A trigger facility based on the IEEE 1588 Precision Timing Protocol that enables modules to have a sense of time that allows modules to time stamp actions and initiate triggered events over the LAN interface.
* A physical wired trigger system based on a LVDS electrical interface that tightly synchronizes the operation of multiple LXI boxes.

The LXI Consortium expects LXI devices to be used in a wide variety of systems, often including devices that are not by themselves LXI compliant. These devices already include IEEE-488, PXI, VXI, M-Modules and LAN instruments with conversion devices where required.

Trigger events over the LAN can be sent by UDP to minimize the latency that can be experienced with TCP/IP protocols. The wired trigger and IEEE 1588 triggers are designed to address concerns about the latency that is sometimes seen in LAN based systems. The defined wired trigger facility provides a triggered mode of operation that emulates trigger signals based on direct point to point connection between legacy instruments. The IEEE 1588 facility allows triggers to be scheduled or events to be time stamped against a system clock.

LXI Devices include web pages that can be opened with any web browser on any computer platform to view and change various parameters the LXI Device has been set to. [http://www.lxiconnexion.com/articles.shtml#Web%20Pages%20Go%20Beyond%20the%20Basics] LXI devices are programmed using standard IVI drivers.

LXI Classes

The LXI Standard defines the following functional classes of instrument to meet the requirements of different applications:
* Class C. Provides a standardized LAN and web browser interface that is compliant with the LXI Standard.
* Class C Plus. Provides a standardized LAN and web browser interface that is compliant with the LXI Standard and physically wired trigger bus (WTB) interface.
* Class B. Provides a standardized LAN interface and supports the IEEE 1588 timing aspects.
* Class A. Provides a standardized LAN interface, IEEE 1588 operation and physically wired trigger bus (WTB) interface. At the present time the vast majority of LXI devices are Class C compliant. These classes do not imply any particular physical size for an LXI Device.

LXI Software

Software packages whose companies endorse LXI for developing test systems are (in alphabetical order):
* LabVIEW and LabWindows/CVI from National Instruments
* MATLAB from The MathWorks
* Measure Foundry from Data Translation
* VEE from Agilent

Note: Microsoft, with Visual Studio including Visual Basic, Visual C++, Visual C# and Visual J#, also provides software solutions but is not a member of the LXI Consortium.

LXI Versus PXI and VXI platforms

Since the introduction of LXI there has been significant debate regarding competition between LXI and the established instrumentation platforms of PXI and VXI. However the LXI Consortium has promoted the concept of hybrid systems incorporating LXI working together with PXI or VXI modular platforms.
* November 2006, both Keithley Instruments and Agilent [http://www.lightreading.com/document.asp?doc_id=111731] [http://www.evertiq.com/newsx/read_news.aspx?newsid=5820&cat=0] , who are both founding members of the LXI consortium, entered the PXI marketplace.
* Significantly, in May 2007 Agilent joined [http://www.marketwire.com/mw/release_html_b1?release_id=246466] the PXI Systems Alliance, during the same month National Instruments formally joined the LXI consortium at Sponsor level, so both competing companies have now simultaneously endorsed and supported standards originally created by the other.
* PXI, VXI and M modules may now be used within the LXI environment using chassis from Pickering Interfaces, VXI Technology and C & H Technology respectively.

LXI Timeline and Standard Revision History

* Formation of LXI Consortium September 2004.
* LXI 1.0 released September 2005.
* First LXI products certified December 2005.
* LXI 1.1 revision released August 2006.
* LXI 1.2 revision released October 2007. [http://www.lxistandard.org/about/lxi_standards_and_clarifications/]
* LXI 1.3 revision in preparation.
* LXI 2.0 now in early development.

LXI Products

The LXI Standard is succeeding the formerly dominant [http://www.tmworld.com/article/CA6555140.html] GPIB or IEEE-488 Instrumentation Bus (originally launched in the early 1970s) as the primary communication bus for instruments. To ensure interoperability and a consistent user experience all LXI Products must go through a strict approval process before being permitted to use the LXI Logo. LXI Products are currently available from the following vendors (by release date): Agilent, Pickering Interfaces, Elgar, Keithley Instruments, Rohde & Schwarz, VXI Technology, C & H Technologies, Kepco, Aeroflex, Goepel, Data Translation, Rigol Technologies. Several other manufacturers have prototypes awaiting conformance testing [http://www.lxistandard.org/press/pr/LXI-12th_PlugFest_meeting_08final.pdf] . Instrumentation already available in LXI includes:-
* Oscilloscopes
* Digital multimeters (DMM)
* Switches and attenuators
* Power supplies
* Power meters
* Signal generators
* Multifunction mainframes
* Function and arbitrary waveform generators
* Thermocouple instruments
* Signal analyzers
* Spectrum analyzers
* Vector network analyzers
* RF and microwave network analyzers
* LCR meters
* Synthetic Instrument (SI) Function/Arbitrary Waveform Generators
* SI RF/Microwave downconverters
* SI RF/Microwave upconverters
* SI IF digitizers
* JTAG/Boundary Scaners
* Event detectors
* LXI 1588 Trigger Box and event detectors
* LXI Wired Trigger Bus (WTB) accessories and cables
* LXI Bridges

References

* [http://www.lxistandard.org/ The LXI Consortium web site]
* [http://www.lxiconnexion.com/ LXI Magazine]
* [http://www.tmworld.com/blog/1330000133.html/ Topical LXI Blog from Test and Measurement World magazine]
* [http://www.pickeringtest.com/lximate LXImate Book provides overview of LXI Standard and usage]