Smartphone based ubiquitous sensing platform leveraging audio jack for power and communication

With the popularization of smartphones, various smartphone centric ubiquitous sensing applications, which use a smartphone in conjunction with external sensors for data acquisition, processing, display, communication, and storage, have emerged. Because smartphones do not have a universal data interfaces, many ubiquitous sensing applications use the earphone and the microphone channels of the 3.5mm audio interface for data communications so that they can work with various types of smartphones. The earphone channels of the 3.5mm audio interface can only send AC signal out of a smartphone, hence DC power needs to be harvested from the earphone channels. In this research, 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 using the same earphone channels. The joint power harvesting and communication technology is demonstrated with a prototype system, which can power an external microcontroller and sensors through the 3.5mm audio interface of a smartphone, display sensor measurement results on a smartphone, and control the outputs of the microcontroller from a smartphone. The newly proposed smartphone sensing platform is expected to harvest double or more power from both earphone channels in comparison to single channel harvesting designs and hence has the potential to support more smartphone powered sensing applications. Furthermore, the sensing platform is expected to support a reliable communication with much higher data rate from a smartphone to external sensors than existing designs