A joint power harvesting and communication technology for smartphone centric ubiquitous sensing applications

With the popularization of smartphones, various smartphone centric ubiquitous sensing applications have emerged, which use a smartphone in conjunction with external sensors for data acquisition, processing, display, communication, and storage. Because smartphones made by different manufacturers do not have a common data interface, many ubiquitous sensing applications use the 3.5mm audio interface for communications so that they can work with different types of smartphones. The 3.5mm audio interface cannot provide DC power to external sensors. Thus, power needs to be harvested from an earphone channel. The existing technology uses one earphone channel to transfer data from a smartphone to external sensors and harvest power from the other earphone channel. Consequently, for many smartphones the technology cannot harvest enough power to support external sensors. In this paper, based on frequency shift keying (FSK) modulation scheme, we have proposed a joint power harvesting and communication technology that can simultaneously harvest power and transfer data with the same earphone channels. Circuit measurements show that by coherently harvesting power from both earphone channels, the proposed technology can extract more than two times of power as from one earphone channel. Meanwhile, demodulation tests show that our newly developed timer-based FSK demodulator can reliably recover the data transferred from a smartphone to external sensors without any error.