Ultra-Low-Power Inter-Integrated Circuit Implementation for Fabric-Based Self-Powered Systems

With the advance of various energy harvesting and storage devices, self-powered wearable systems have gained significant interest in the past few years. In addition, the growing focus on fibers with digital devices is driving the potential for fabrics with digital systems for health monitoring and human-machine interfaces. While such digital-enable fabric systems consist of various distributed digital devices, a low-power serial communication component is in high demand. The standard Serial Peripheral Interface (SPI) commonly used in device connection is unsuitable for communication in fiber because the bit width of the slave select signal (SS) increases with the number of networked devices.

To address this research gap, we propose using Inter-Integrated Circuit (I2C) for communication in fiber and presenting the SPI-I2C Protocol Converter chip for data transfer from the SPI to the I2C bus. Our research involves designing and implementing a low-power I2C module with tunable frequency, data width, and output voltage. The I2C module on the chip can work at 0.4 V supply voltage with only 2.6 nW static power. In addition, we designed the I2C controller on the chip that can adaptively adjust the drive capability to balance power consumption and reliability when more devices are connected. Finally, we integrate the I2C module into the System-on-Chip (SoC) using the ARM Advanced Peripheral Bus (APB) to complete the digital-enabled fabric system.