Internet-of-microchips: direct radio-to-bus communication with SPI backscatter

Energy consumption of Internet-of-Things end devices is a major constraint that limits their long-term and large-scale deployment. Conventionally, the radios and processors used in these end devices are major power consumption that drains at the level of milliwatts (mWs). However, in recent decades, backscatter communication has dramatically reduced the power consumed by the radios in end devices to microwatts (μWs), and thus the processor remains the major bottleneck for energy optimization.In this paper, we propose a processor-free architecture as a novel design that allows the radio to interface directly with peripheral sensor chips for control and data collection, thereby separating the processors from the end device design to significantly reduce the energy consumed by end devices. The main problem is that the peripheral chips are designed to be accessed by the processor via a standard digital bus and they cannot communicate directly with the radio. In order to support such processor-free design, we propose radio-to-bus (R2B) as a novel communication paradigm that allows direct data exchange between a backscatter radio and the serial peripheral interface (SPI) bus. We implement the processor-free architecture in proof-of-concept prototypes and demonstrate that the power consumption decreases by 4.5 times compared with the conventional end device design.