Paul Parkinson

Case study: Ultra Datel safety-critical avionics upgrade using COTS

I recently had the privilege of working with one of our partners, LDRA, and one of our customers, Ultra Datel, on writing a case study of their experiences of a mid-life upgrade of an existing avionics system.

What caught my attention was the fact that the existing system was uncertified, and the upgrade involved migrating the existing system to a commercial-off-the-shelf (COTS) and undertaking DO-178B Level B safety certification.

As a result, the project faced a number of development challenges because the pre-existing software and device drivers were not developed with safety certification in mind, and the code needed to be re-engineered and modified to meet safety certification requirements.

In the case study, we discuss the following development challenges and how they were overcome using the LDRA Tool Suite during the development of the safety-critical VxWorks application running on a GE Intelligent Platforms ruggedised PowerPC platform:

1. Porting to the VxWorks DO-178B safety-critical subset
2. Reduction of high cyclomatic complexity
3. Programming language subset compliance
4. Code coverage to meet DO-178B Level B objectives

The case study has now been published on the Wind River website on the Aerospace & Defence customers page (and the PDF file can be accessed directly here).

Rhapsody && Coverage Analysis

I've recently been working with a customer to integrate Wind River Coverage Analysis (formerly known as CoverageScope) with Telelogic Rhapsody within their development tools framework for a mission-critical system.

At first glance, it might seem strange to integrate a code coverage testing tool with a UML design tool, as these aren't even adjacent phases in the software development life cycle (implementation being between them). However, the advent of Eclipse in recent years has helped to break down the silos which used to confine tools individual development life cycle stages and improved development work flow.

The integration enables an application to autocode-generated from Rhapsody and built with Coverage Analysis instrumentation and downloaded and run on the target processor, with coverage results being continuously streamed back to the host and displayed in the Coverage Analysis GUI. This provides immediate feedback of of the level of coverage, and the coverage trend against time (useful for confirming if the test suite tests more and more code over time, or whether it is testing the same code over and over again).

The aspect of the integration which left the biggest impression on me though, was how it enabled the customer to confirm that the right code is executed in response to an event being injected at the UML model level. This is an important aspect of system testing, and it is often difficult to demonstrate the traceability from design to implementation. This was achieved by building the application with both Rhapsody animation and Coverage Analysis instrumentation, and then run or animated on VxWorks with events being injected from Rhapsody and the executed code was shown in Coverage Analysis.

If you're interested in seeing this for yourself, the integration steps are now documented in AppNote-344 on Wind River Online Support website (login required).