Rainbow: An OS extension for hardware multitasking on dynamically partially reconfigurable FPGAs

DPR (Dynamic Partial Reconfiguration) capability found in some of modern FPGAs allows implementation of a concept of a HW (Hardware) task, which similarly to its software counterpart has its state and shares time-multiplexed resources with the other tasks. While the new technology presents many advantages for embedded systems where run-time adaptability is an additional requirement, their efficient and easily portable implementations require a control software or an OS which would manage all the complexities of the underlying technology, providing an abstracted interface for the application programmer. This paper presents a novel and robust hardware multitasking extension for a conventional OS, managing task scheduling and configurations, and providing easy-to-use API (Application Programming Interface) for the application programmer. Scheduling is priority-based and takes advantage of task caching. Moreover, the extension is based on a developed design flow and embedded hardware platform allowing efficient task preemption, which can be utilized whenever it presents any benefits to the application.