Ethernet POWERLINK in test now

By: Carsten Emde

Real-time Ethernet for real-time Linux

In addition to the existing real-time Ethernet tests, there is now a Powerlink test bed. It consists of a standard computer system running OSADL's "Latest Stable" real-time mainline Linux kernel that is equipped with version 1.7.1 of the Open Source Powerlink master stack. This stack is licensed under the BSD license which makes it possible, in contrast to some other real-time Ethernet protocols, to use Powerlink in the Linux kernel without any license restrictions. In addition to the implementation as Linux kernel module used in this test bed, the latest version of the Powerlink stack optionally can be used as user space application and, thus, complements the existing kernel space variant.

At the OSADL QA farm, the Powerlink master stack runs on an Eltec Eurocom 400/Modbase 200 system (see below); it is located in rack #4, slot #5. Its profile is available here, and its most recent latency plot can be inspected here. Using a stock Ethernet adapter, the system is connected to a B&R Powerlink I/O node, and the network communication is sniffed continuously using a B&R Powerlink network analyzer (see Figure below). The 5-min cycle interval data and the derived jitter are publicly presented on the Internet in the same way as the other continuously recorded real-time data of the processor and board section and the Ethernet section of the farm.

Eltec EUROCOM 400

The Eltec Eurocom 400 (E400) COM Express module is equipped with a dual-core Intel Xeon LV 2.0-GHz CPU. It is living in rack #4, slot #5 of the OSADL QA Farm. The entire profile of the board is available here. The most recent latency plot (here) shows excellent real-time capabilities of the processor and the board. At the OSADL QA farm, the E400 module is mounted on a COM Express carrier (Modbase 200) that is also available from Eltec. In addition to the on-board Gigabit Ethernet network adapter, a secondary stock network PCI Ethernet adapter was installed to serve as a peer to test the Open Source Powerlink master stack under Linux (see below). The successor board of the E400, the Eltec Eurocom 450, is very similar to the E400 except that the processor is an Intel Core 2 Duo running @1.5 GHz or @2.16 GHz; in addition, it has 4 MByte L2 cache instead of 2 MByte.