Silicon Witchery's S1 Packs nRF52 and iCE40 FPGA Into a Small, Battery-Friendly TinyML Module

Swedish embedded specialist Silicon Witchery has released an incredibly compact module designed to bring Nordic Semi nRF52840 connectivity to the most space-constrained of projects — and, somehow, has found room to cram a Lattice iCE40 field-programmable gate array (FPGA) on there too.

"Designed for efficient AI on the smallest edge devices," Silicon Witchery claims of its combined microprocessing and FPGA device. "The S1 aims to simplify your design and save you months of RF HDI [radio-frequency high-density interconnect] layout. The S1 is a union of four key components that are critical to developing tiny battery-powered products. It targets applications requiring demanding algorithms while consuming as little energy as possible."

Despite its diminutive dimensions of just 11×6mm (around 0.43×0.24") the S1 Module, brought to our attention by CNX Software, packs in four key blocks: A power-management integrated circuit (PMIC) with buck-boost converter, low-dropout regulator, and battery charging capabilities; 32Mb of external SPI flash for storage; a Nordic nRF52840 system-on-chip with 64MHz Arm Cortex-M4 microprocessor; and a Lattice iCE40 FPGA with 5k LUTs and dedicated DSP cores.

Between the microprocessor and FPGA, Silicon Witchery claims, it's possible to run always-on inference tasks at the edge while drawing as little as 75µA of power. At the same time, an integrated antenna provides wireless connectivity over Bluetooth 5.2, with Long Range and Thread support. In total, the module includes two general-purpose input/output (GPIO) pins from the nRF52 with analog-to-digital conversion (ADC) and low-power wake support plus an additional eight GPIO pins from the FPGA, including I2C, I3C, SPI, and USB, alongside three adjustable Vout rails with a single buck-boost up to 5.5V.

Alongside the tiny module itself Silicon Witchery has released two development kits: The S1 Popout Board, which provides breakouts for the module's IO functions and a debugging port for the Cortex microprocessor plus a handy port for a lithium-polymer battery and a StemmaQT/Qwiic-compatible port for external sensor hardware; and the S1 ECG Kit, which uses the module to drive a low-power three-probe electrocardiograph with integrated lithium-polymer battery and an on-board LED bar graph.

Full details on the module and development boards can be found on the Silicon Witchery website, where the module can be ordered for $30 per unit and the Popout Board and ECG Kit for $39 and $45 respectively.