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Diagnostics for MOST system

Posted: 21 Mar 2014     Print Version  Bookmark and Share

Keywords:infotainment network  MOST  Electrical Control Line  ECL  TTsuite 

The test cases in the MOST Extended Core Compliance Test Specification: Electrical Control Line of the MOST Cooperation are written in the Graphical Format of the TTCN-3 (GFT) as executable test specifications. The ECL test suite is generated out of these GFTs by TTsuite. This kind of test development process provides a reliable test specification and eliminates the chance of misinterpretation from the very beginning.

TTsuite is able to handle very different communication protocols via adapters. ECL is similar to the LIN bus, therefore TTsuite has an adapter to be able to decode the ECL pulses into data for testing purposes and code the data into pulses for the simulation. Tests regarding the reaction of the DUT to ECL protocol violations by changing the pulse width are reliably executable with TTsuite.

Information is transferred via pulse state and pulse width on the ECL as a bidirectional bus line. It has two states: high, logical 1 (supply voltage) and low, logical 0 (ground). The default state is high. The ECL sequence chart (see top of Figure 1) shows the results of a system test from the ECL specification; below that is a corresponding oscillogram of an ECL system test alive sequence. It begins with the start sequence with 7 sec start up time, followed by the parameter sequence 10000 and the result sequence with results from node class 4 till node class 19. (An oscilloscope is used only for display purposes, not for the measurements.)

Figure 1: System test from the ECL specification with the corresponding oscillogram of an ECL system test alive sequence underneath.

Efficient test environment for reliable networks
TTsuite is able to control any additional tools needed for the test setup. In this case, TTsuite controls the Ruetz System Solutions ECL/CAN Box and Breakout Box, with OptoLyzer and a Power Supply (see Figure 2: Test setup ECL test automation). The MOST bus of the test setup is set via the OptoLyzer module. The ECL bus is formed by the ECL/CAN Box. The Breakout Box is a device for configuring the test setup. This hardware interface serves as an expansion of the TTsuite test bench in order to automatically execute the test setup described in the test specification. It is connected to the Power Supply of the DUT, and to the ECL line of the DUT. The ECL/CAN Box is a device for sending wake-up and test sequences of the ECL and for receiving subsequent replies from the DUT and forwarding them via the interface to the TTsuite. (Apart from this, connected control devices can be woken up by CAN messages by the ECL Box.)

Figure 2: Test setup ECL test automation.

The documentation of the test results is fundamental in the compliance verification process. It shall include detailed information about the behaviour of the DUT and recommendations for improvement if necessary. TTsuite provides a test report with a chart about the test result, to get a statistical overview. TTsuite also provides a graphical test protocol, which has the same structure and look as the test specification of the MOST Cooperation. So it is very easy to analyse and understand the test protocol and to compare it to the test specification.

This new, fully-automated ECL test system ensures global consistency regarding test results. The benefits of using this test system are apparent. Executable test specifications, detailed documentation of test results, easy-to-analyse test protocols provide transparency and allow unambiguous, clear communication between tester and developer regardless whether the tester sits in a MCTH or in-house with the developer. The devices can be validated using this test system from the beginning of the development via in-house tests.

References
1. Electrical Control Line Specification Rev 1.0 10/2008, Rev 1.0.1 06/2009, Rev 1.1 11/2010, Rev. 1.1 ERRATA SHEET Rev. 1.0 07/2011, Rev 1.1.1 11/2011
2. MOST Extended Core Compliance Test Specification: Electrical Control Line Rev 1.0 07/2012
3. TTsuite Test Development Kit: making test projects effective and unambiguous, Ruetz System Solutions, MOST Interconnectivity Asia, 2011

About the author
Dr. Terezia Toth works as Senior Consulting Engineer at the MOST Compliance Test House of Ruetz System Solutions GmbH in Munich, Germany.

To download the PDF version of this article, click here.


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