Developing a Custom Hardware-in-the-Loop Test System

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Software testing accounts for 50-70\% of the software development life cycle within safety-critical aviation systems. As software complexity on board commercial airliners continues to increase, costs due to software testing continue to escalate. Manual tests provide low up front costs but tend to be slow and costly to execute, and the results are often subjective. Automated tests significantly accelerate test execution times and ensure objective test results. Many existing automation solutions require multiple components for the different communication protocols and a high level of technical expertise of these communications protocols. This paper presents a custom Multi-level Hardware-In-the-Loop (MHIL) test system that integrates all communication interfaces to the system under test into a single well synchronized platform and uses this integration to provide intuitive test development environments. The MHIL system uses a System-on-Module to integrate FPGA and Real-Time Operating Systems to provide precise and synchronized control across a wide variety of communication protocols. Layered abstraction translates from these low-level complex hardware protocols to high-level test functions that would be very recognizable to anyone familiar with the user interfaces of the system under test. Results from case studies demonstrate significant improvements in test execution time when using this system. With this automated testing, execution of individual test procedures show improvements of up to 20 times, and complete projects have seen test execution times more than 15 times faster, while also providing more precise and repeatable test results.