Investigating LXI Functions of Measurement Instruments

28 January 2019 | Article

Using a test solution consisting of hardware and software, the LXI functions on measuring instruments can be investigated and verified. A connection to the network helps to automate the test.

The LXI functions of a measuring instrument can be verified with a special hardware and software solution. The advantage of the Kerberos system developed by TSEP is that the hardware is viewed in isolation and the software is an integral component. The test platform can be used to test both hardware and software. On the hardware side, all necessary components for testing are included. The Device-Under-Test (DUT) can be connected via several interfaces such as LAN, USB, I²C or RS232.

The hardware is controlled via one of the network interfaces. Thus, the platform creates a test environment without external influences on the test object. Even if a device is connected and tested via LAN, the physically separated network cards decouple the test network from the local network. This makes it clear that several network interfaces are available. Two of the network interfaces are routed to the outside, which serve to connect the client PC and optionally the device under test (DUT). Another network interface is only used internally to simulate another device in the test network. This is necessary, for example, to test the protocol 1588. It can be determined whether a device can cope with several devices in the network.

Automatic test thanks to network

All network interfaces are switched internally to achieve the appropriate combination for the selected test. A peer-to-peer connection or a connection via a switch is possible. In addition, the hardware of the TSEP Kerberos is capable of independently disconnecting the DUT from the network or connecting it to the network. This increases the automation of test procedures. All tests can be automated via the built-in router, as the software monitors all changes to the router. The hardware represents the server in a client-server concept.

All actions are executed on the server, but the client is only a tool which reflects the current status of the server and offers the possibility to configure the server and start tests. The display on the hardware shows a small statistic: This includes how many tests are included in the test scope and how many of them were successful and unsuccessful. In addition, there is a detailed log of all actions performed by the server. This log can be displayed in more or less detail.

In the client software, the individual logs are assigned to the corresponding tests so that each test has a detailed log. This makes it possible to track how an error occurred. A test always consists of preconditions, the actual test and postconditions. Preconditions are the settings that must be made to have a suitable setup to run the test. These include router settings or whether the DUT is connected to the network at the beginning of the test. This means that the same requirements always apply when a test starts. In addition there are defined test-specific steps and finally the post-conditions are checked. This could be a validation of the received IP address of the DUT or that the DUT address has been entered in the mDNS.

Results are output as PDF files

Once all necessary tests have been completed, a summary of the results is useful. The user receives this as a PDF file via the client. The PDF is created on the server and signed by the server. Thus it cannot be manipulated without losing the signature. To control the server, it is also irrelevant whether the TSEP Kerberos is connected to the client via a peer-to-peer connection or simply connected to the local network. This is because the client searches and lists all available Kerberos servers. You can connect via this list. However, each server only allows one single client. This means that an existing connection must first be closed before it can be accessed from a second PC in the network.

The platform also provides a command line tool so that Kerberos can be operated by programs or scripts. This makes regression tests possible, for example. This is helpful for continuously checking the functionality of a device during further development. The console client can also be used to create and configure test sessions and to find all Kerberos hardware on the network. All possibilities of the interface client are also available in the console client. Only manual tests cannot be performed with the console, as this requires user interaction, which is only possible via the client.

Another advantage is that tests can also be logged. Individual steps are closely tracked and documented to allow easy debugging of the problem. How detailed the recording is can be set via the client itself. Thanks to the modular structure, the user can purchase individually adapted modules to test core functionalities on his own devices.

Comparison Kerberos - LXI Conformance Test Suite

TSEP Kerberos was originally developed for LXI measuring instruments. The previous software solution for testing the LXI functionality required additional hardware. A suitable router, which provided all necessary parameters for configuration, was not easy to find. Individual hardware components no longer need to be searched for with the Kerberos platform. The manufacturer offers its own hardware components to increase the level of automated testing for the LXI functionalities.

Further hardware is not necessary as for example in comparison to the LXI Conformance Test Suite. The only requirement is a PC on which the Kerberos client is installed. TSEP Kerberos also ensures that the results obtained are compatible with the LXI Conformance Test Suite. Kerberos adapts changes to an LXI test. Therefore, the compatible LXI Conformance Test Suite version is specified in the information on the server. Currently, Kerberos supports the majority of LXI components. These include the LXI Device Specification 2016 and the Extended Features LXI HiSLIP, LXI IPv6 and LXI VXI-11 Discovery and Identification.

Planned extensions for the LXI variant are the "LXI Clock Synchronization" and the "LXI LAN Event Messaging Tests". It is also planned to implement "LXI Security", in which the LXI consortium is making great progress. Possible updates can be imported via a USB stick. A variant of a pure IEEE1588 test environment is also planned. The Kerberos platform will be merged with Herakles in 2019. TSEP has been continuously developing this platform for years and it will be used internally for testing software components.

Author / Editor: According to material from TSEP / Hendrik Härter

Reference: https://www.elektronikpraxis.vogel.de

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