Model-based Development for Event-driven Applications using MATLAB: Audio Playback Case Study

Audio playbacks are mechanisms which read data from a storage medium and produce commands and signals which an audio system turns into music. Playbacks are constantly changed to meet market demands, requiring that the control software be updated quickly and efficiently. This paper reviews a 12 month project using the MATLAB/Simulink/Stateflow environment for model-based development, system simulation, autocode generation, and hardware-in-the-loop (HIL) verification for playbacks which read music CDs or MP3 disks. Our team began with a “clean slate” approach to playback architecture, and demonstrated working units running production-ready code. This modular, layered architecture enables rapid development and verification of new playback mechanisms, thereby reducing the time needed to evaluate playback mechanisms and integrate into a complete infotainment system. A system simulation environment which included a real-time operating system supports generic mechanism and behavior models, to account for functional differences in playback mechanism from different suppliers. The execution of HIL system simulation required the design and implementation of a communication protocol device which transceives command messages passed between the system environment and the playback mechanism. With this harness, either a generic mechanism model or a hardware unit can be tested, allowing development of mechanism control software before production system hardware platforms are available. Specification-derived test vectors are used as functional tests during development and results have been used during the verification of auto-generated production software against the model. A comprehensive application of executable specs to audio playbacks is successfully demonstrated, including important considerations such as configuration management, model library management, and requirements traceability. Limitations and benefits of this approach are described, along with lessons learned in the implementation of model-based design in the field of automotive electronics.