System Design Trade-Offs in a Next-Generation Embedded Wireless Platform

Over the course of the past decade, the evolution of advanced low-energy microcontrollers has raised three questions which this paper outlines and addresses. The first question is: Can a 32-bit platform be constructed that provides advanced features but fits within the energy constraints of a wireless sensor network? We answer this in the affirmative by presenting the design and preliminary evaluation of Storm – one such system based on an ARM Cortex-M4 that achieves 2.3μA idle current with a 1.5μS wake up time. The second question we answer is: Can this platform simultaneously meet the very different demands of both monitoring-type applications and cyber-physical systems? We demonstrate that this is indeed possible and present the design trade-offs that must be made to achieve this, yielding a module with a rich set of exported peripherals that fits in a 16mm x 26mm form factor. The final question explored by this paper is: If such a platform is possible, what new opportunities and challenges would it hold for embedded operating systems? We answer this by showing that the usage of modern 32 bit microcontrollers requires reconsidering system architecture governing power management, clock selection and inter-module dependencies, as well as offering opportunities for supervisory code and the coordination of common tasks without CPU intervention.