EMI- and Energy-Aware Scheduling of Switching Power Supplies in Hard Real-Time Embedded Systems

In this paper we present the Make And Take (MAT) approach for adding switch-mode power supply (SMPS) control to hard real-time systems. MAT enables control of the SMPS with the task scheduler and this allows the designer to use a less expensive and smaller (but noisier) SMPS without it affecting circuits sensitive to electromagnetic interference (EMI) such as high-impedance input signals and amplifiers. The MAT concept is both energy and EMI aware and schedules the tasks based on the total energy in the system by segregating them as either a producer or consumer of energy. We discuss MAT in detail and show how it can be applied to both preemptive and non-preemptive scheduling approaches. We present several properties of MAT and their impact on the system, in terms of energy and real-time scheduling decisions. We demonstrate its usage by implementing a simple processor controlled boost SMPS on a non-preemptive real-time embedded platform.