Onboard Software Inc. provides a wide range of high-technology services including re-engineering of existing electronics and software systems. Their customers include military and avionics projects as well as commercial applications.

Re-Engineering

Recently the US Air Force asked Onboard Software to re-engineer a data acquisition system used on one of its cargo aircraft. This avionics subsystem monitors several hundred sensors and is used by the flight engineer to track the status of the aircraft and troubleshoot any problems. The processing capacity of the system was near capacity, and had no additional headroom to allow the addition of new functionality. Furthermore, it was outdated and poorly documented, making it difficult to maintain. Onboard Software was contracted to re-engineer both the hardware and the software, to produce a new subsystem that maintained all the current functionality but provided additional headroom for new features. The first step, was to identify the functionality in the current system's hardware and software. The problem was, most of the system documentation was either outdated or missing. OnBoard's challenge therefore, was not only to discover all of the functionality, but to document it sufficiently so that a new system could be built and verified to have equivalent functionality as well as substantial extensibility.

Support Architecture

Onboard Software chose ARTiSAN Real-time Studio® for its unique combination of systems, software and hardware engineering support for real-time systems. Only Real-time Studio provides a System Architecture modeling environment for the hardware and HW/SW interfaces, in addition to being a rich environment for object-oriented development of new systems. Senior Software Engineer Sam Stockbridge has particularly focused on two aspects of the current system; identifying and capturing the intended functionality as UML use cases, and diagramming the hardware architecture, which includes numerous boards, buses, interfaces, and hundreds of sensors.

Documentation

"Given that the current system had almost no documentation, how could we ask our software engineers to perform anything but the most basic maintenance tasks, which involved nothing more complex than textual changes to display information? Changing or adding software functionality was difficult to plan from a program management aspect, and difficult to execute technically since it usually involved manual code tracing of existing task threads, which could take weeks for a single thread. It's a painstaking process, but we have iteratively captured each functional operation of the subsystem as UML use cases in Real-time Studio. We also have successfully captured the hardware architecture and all the interface details that engineers need to perform maintenance. This means that our software engineers now have an on-line reference covering the current functionality and the hardware that their software must communicate with. And it also means we can readily publish up-to-date system documentation."

Design, Define

However, OnBoard's use of Real-time Studio is not limited to documenting the existing system. They are designing new hardware, using the System Architecture features to describe the hardware architecture and interface details prior to board and circuit design. And with the currently supported functionality captured in RtS use cases, they can be confident that no functionality will be overlooked as they begin implementing the new software. "In fact, as we add new functionality to the system, we will define the use cases and scenarios, and design our object architecture using Real-time Studio's object modeling feature set," Sam adds.

"The beauty of Real-time Studio, is that doesn't just provide a means of documenting the existing system. Since it supports UML and an object-oriented approach, it's a perfect environment for us to model new functionality in the new system. What we've found is that with all of the existing system's functionality and architecture captured in Real-time Studio, our software engineers have a centralized shared model upon which they can base their new hardware and software design and functionality. Since ARTiSAN's Real-time Perspective supports an iterative development approach, it fits well with our desire to add functionality in steps."

What was the hardest part about getting started with Real-time Studio? Sam explains: "The tool itself is quite straightforward to use. But for us, UML was a new language for describing functionality, and it took some getting used to. However, the training class ARTiSAN gave was really useful. And now after a couple of months we're so comfortable with UML diagrams and the other real-time diagrams in Real-time Studio, that we project them from a laptop during our review meetings."

The Future

"This approach with Real-time Studio will form the basis for replacement of the existing paper-based software engineering processes in place at Onboard As Onboard develops expertise with Real-time Studio, the tool will gradually be incorporated into other projects with each team sharing their 'lessons learned.' Eventually, Real-time Studio and UML will be the standard process for our avionics systems development, management information systems, jet engine testing, and our Internet solutions business."