Basswood: BALSA in Real-time

Real-time performance is a critical aspect of avionics computing. The Basic Avionics Lightweight Source Archetype (BALSA) exemplar provides a collection of Units of Conformance (UoCs) backed by a Future Airborne Capability Environment™ (FACE) Unit of Portability (UoP) Supplied Model (USM) running in a Linux desktop environment. This gives an easy-to-run example for users of the FACE Technical Standard and effectively illustrates the conformance aspects of the FACE Technical Standard, but is not intended to run with hard real-time constraints. To address this limitation, we developed Basswood, a BALSA-based exemplar using components aligned to the FACE Technical Standard running in a real-time environment. Basswood runs on Real-Time Executive for Multiprocessor Systems (RTEMS), an open source Real-time Operating System (RTOS). Further, Basswood facilitates a practical demonstration of model-based systems engineering using the Architecture Analysis and Design Language (AADL). Basswood helps demonstrate how combined use of the FACE Technical Standard and AADL allows application of virtual integration analysis methods to FACE UoCs. This paper describes the lessons we learned adapting BALSA to a real-time environment and introduces readers to virtual integration analysis with the FACE Technical Standard and AADL.