ZeroScatter: Zero-Added-Component Backscatter Communication Using Existing Digital I/O Pins

Abstract

ZeroScatter is an ultra-low-cost, zero-added-component approach that enables backscatter wireless data uplink from billions of existing, commodity microcontrollers (MCUs) and field-programmable gate arrays (FPGAs). Existing MCU and FPGA based backscatter wireless sensors rely on external components such as RF FETs, PIN diodes, or varactors to perform the backscatter modulation function. We demonstrate that completely unmodified digital I/O pins on MCUs and FPGAs can be re-purposed as BPSK backscatter modulators in the UHF/microwave bands. The ZeroScatter temperature sensor tag prototype presented here uses only two components: a PIC12LF1552 8-bit MCU that costs less than $0.50 USD, and a 3 V lithium coin cell battery. A wire dipole serves as the antenna. We demonstrate BPSK backscatter modulation of an incident 915 MHz industrial, scientific, and medical (ISM) band carrier with 32-bit packets containing a tag unique-ID, an on-chip temperature reading, and a cyclic redundancy code (CRC) checksum. At a data rate of 9.4 kbps, with an externally supplied carrier power of +10 dBm, a range exceeding 3 m is demonstrated in an ordinary office environment. In active operation, the ZeroScatter tag consumes only 628 μA at 3.0 V or 473 μA at 1.8 V, including temperature sensing, processing, and backscatter functions.