Friday, October 19, 2007

Linux on test systems, pt 2

Back in mid-July I talked about a new series of Agilent white papers on using Linux in test systems. Well, the second paper in the series, "Using Linux to Control LXI Instruments through VXI-11," has just come out.

The paper begins by defining VXI-11: the GPIB equivalent for controlling instruments via Ethernet. It was added by the VXI Alliance in 2000. The other method the VXI group added, direct TCP socket communications, is a lower-level protocol. This paper maintains that VXI-11 is better for most cases.

It then proceeds to talk about Remote Procedure Calls (RPC). VXI-11 is based on RPC, so Linux will directly support VXI-11 (no $500 GPIB cards or expensive cabling required). To use RPC, Agilent promotes using the rpcgen code generator. They supply several different code examples using generated code.

In general, the white paper was organized, the author knew the subject, and the narrative flowed well from beginning to end. But this paper was not a Linux paper. Other than stating that you can use RPC in Linux (obvious), the paper is really just about VXI-11. To cap it off, the name "Linux" is only mentioned FOUR times in the text of the paper.

The paper is really a veiled push for communicating via VXI-11 regardless of the operating system. But as I stated in my original post for this series: white papers tend to be self serving. They are usually generated by the marketing department. And Agilent certainly has a big axe to grind for using Ethernet to access test equipment. All the big names in test equipment are members of the LXI consortium (LAN eXtensions for Instrumentation), but Agilent was an early proponent of the standard. Also, they were the first company to have LXI-certified equipment.


The remaining papers in the series are "Using Linux to Control LXI Instruments through TCP Communication", "Using Linux to Control USB Instruments", and "Using Linux in Soft Real-Time Applications". I'll be reviewing those as they are released. Hopefully the remaining papers will have more substance relative to Linux. Unfortunately, I now harbor doubts.

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