NoLoRa: Ultra-Low-Power LoRa Transmissions Without Active Radios for Battery-Free Devices

This paper presents ”NoLoRa,” a novel method for achieving LoRaWAN-compatible communication without dedicated radio transceivers or batteries. The system leverages electromagnetic emissions from digital signals in low-power microcontrollers. By utilizing the 27th harmonic of square waves generated from Serial Peripheral Interface (SPI) and Inter-Integrated Circuit Sound (I2S) interfaces operating at 16 MHz,NoLoRa generates proper LoRa chirps. Commercial off-the-shelf (COTS) LoRa receivers at 433 MHz successfully decode these signals without requiring active RF components, such as power amplifiers, at the transmitter. The NoLoRa system achieves an average power consumption of 27 µA at a 1% duty cycle, demonstrating its suitability for battery-free operation via energy harvesting. Experimental validation confirms transmission ranges exceeding 100 m. The proposed system enables low-cost, long range wireless communication for applications including remote environmental monitoring, asset tracking in logistics, and smart agriculture sensor networks.