Real-Time Control of I/O COTS Peripherals for Embedded Systems

Real-time embedded systems are increasingly being built using commercial-off-the-shelf (COTS) components such as mass-produced peripherals and buses to reduce costs, time-to-market, and increase performance. Unfortunately, COTS interconnect systems do not usually guarantee timeliness, and might experience severe timing degradation in the presence of high-bandwidth I/O peripherals. To address this problem, we designed a real-time I/O management system comprised of 1) real-time bridges, and 2) a reservation controller. The proposed framework is used to transparently put the I/O subsystem of a COTS-based embedded system under the discipline of real-time scheduling. We also discuss computing a delay bound for I/O data transactions and determining worst-case buffer size. Finally, we demonstrate experimentally that our prototype real-time I/O management system successfully prioritizes I/O traffic and guarantees its timeliness.