Accumulative Display Updating for Intermittent Systems

Abstract

Electrophoretic displays are ideal for self-powered systems, but currently require an uninterrupted power supply to carry out the full display update cycle. Although sensible for battery-powered devices, when directly applied to intermittently-powered systems, guaranteeing display update atomicity usually results in repeated execution until completion or can incur high hardware/software overheads, heavy programmer intervention and large energy buffering requirements to provide sufficient display update energy. This paper introduces the concept, design and implementation of accumulative display updating, which relaxes the atomicity constraints of display updating, such that the display update process can be accumulatively completed across power cycles, without the need for sufficient energy for the entire display update. To allow for process logical continuity, we track the update progress during execution and facilitate a safe display shutdown procedure to overcome physical and operability issues related to abrupt power failure. Additionally, a context-aware updating policy is proposed to handle data freshness issues, where the delay in addressing new update requests can cause the display contents to be in conflict with new data available. Experimental results on a Texas Instruments device with an integrated electrophoretic display show that, compared to atomic display updating, our design can significantly increase accurate forward progress, decrease the average response time of display updating and reduce time and energy wastage when displaying fresh data.