Arnold: An eFPGA-Augmented RISC-V SoC for Flexible and Low-Power IoT End Nodes

A wide range of Internet of Things (IoT) applications require powerful, energy-efficient, and flexible end nodes to acquire data from multiple sources, process and distill the sensed data through near-sensor data analytics algorithms, and transmit it wirelessly. This work presents Arnold: A 0.5-To-0.8-V, 46.83-mu ext{W} /MHz, 600-MOPS fully programmable RISC-V microcontroller unit (MCU) fabricated in 22-nm Globalfoundries GF22FDX (GF22FDX) technology, coupled with a state-of-The-Art (SoA) microcontroller to an embedded field-programmable gate array (eFPGA). We demonstrate the flexibility of the system-on-chip (SoC) to tackle the challenges of many emerging IoT applications, such as interfacing sensors and accelerators with nonstandard interfaces, performing on-The-fly preprocessing tasks on data streamed from peripherals, and accelerating near-sensor analytics, encryption, and machine learning tasks. A unique feature of the proposed SoC is the exploitation of body-biasing to reduce leakage power of the eFPGA fabric by up to 18 imes at 0.5 V, achieving SoA state bitstream-retentive sleep power for the eFPGA fabric, as low as 20.5mu ext{W}. The proposed SoC provides 3.4 imes better performance and 2.9 imes better energy efficiency than other fabricated heterogeneous reconfigurable SoCs of the same class.