Implementation of an Interrupt-Driven OSEK Operating System Kernel on an ARM Cortex-M3 Microcontroller

An operating system usually distinguishes between threads managed by a software scheduler and interrupt service routines, scheduled and dispatched by an interrupt controller. This paradigm has inherent problems for real-time systems as low-priority interrupt routines can interrupt high-priority threads. The Sloth concept proposes to overcome this issue by implementing both interrupt handlers and threads as interrupts, which are scheduled and dispatched by hardware. This eliminates the difference between the two types of control flows by introducing a unified abstraction. With this simplification, scheduling and dispatching of threads can be managed completely by the interrupt subsystem in hardware. In the scope of this thesis, this Sloth concept was implemented as an interrupt-driven operating system conforming to the OSEK specification on the ARM Cortex-M3 microcontroller platform. This entails the investigation how the Sloth concept can be implemented with the provided hardware functionality and how the hardware components need to be utilized. This finished implementation is evaluated and compared to another operating system with a software-based scheduler in order to confirm the positive effect of this concept on the performance of thread management. Additionally, this thesis examines the influences of the hardware architecture on the design and implementation of Sloth.