Scheduling Switch-Mode Power Supply Noise for Real-Time Systems

A Switch-Mode Power Supply (SMPS) is invaluable in its ability to efficiently convert energy, which allows digital logic circuits to operate at the most efficient voltage based upon power and timing parameters, saving power and energy. However, an SMPS introduces noise into the system. Some real-time computing systems contain hardware resources that are rivalrous in nature. These are groups of resources that create or are sensitive to noise − Switch Mode Power Supply (SMPS) and an Analog to Digital Converter (ADC), for example. This paper presents Rivalrous Hardware Scheduling (RHS), a technique that utilizes real-time scheduling concepts for controlling the run-times of such rivalrous hardware via a software scheduler in order to reduce interference among them. As part of RHS, we propose an energy aware scheduling technique, called the Make And Take (MAT) scheduling model, which (1) controls the activity of the SMPS and (2) schedules the tasks based on the total energy in the system in relation to whether they produce or consume energy. We demonstrate and prove the concept of RHS using MSP430-based low-power embedded nodes. By implementing a processor controlled SMPS on these nodes, we study the negative impact of adding an SMPS in the system and show how it can be overcome by using the principles of RHS. Keywords-rivalrous; interference; hardware scheduling; processor controlled SMPS; energy aware scheduling;