Microsecond Time Synchronization for Computing Fiber Networks

Abstract

We present a microsecond-accurate time synchronization method and time localization system for a sensor network of spatially-separated, low-power Bluetooth nodes, with the goal of integrating this system into thermally-drawn computing fibers. Each node consists of an nRF54L15 SoC paired with an ICS-43434 digital I2S microphone, enabling synchronized audio data collection. Our design leverages Bluetooth LE connection events to synchronize local clocks with sub-10 µs accuracy across a multi-peripheral topology; we trigger precise, CPU-independent hardware events to timestamp audio samples. We demonstrate that timestamped I2S data stored in external SPI flash can be correlated across devices to extract TDoA measurements for localizing sound sources. Cross-correlation techniques allow us to estimate direction and position, with localization errors reduced from 4.17 m to 0.39 m through clock synchronization. This prototype provides a roadmap for embedding synchronized sensing and computation within fibers and smart textiles, with implications for on-body audio perception and distributed sensing in flexible electronics.