What Witchery Is This Tiny Low Power Bluetooth FPGA module?

Aptly named Swedish hardware developer Silicon Witchery has released the S1, a tiny module combining a Nordic Semiconductor nRF52840 and a Lattice iCE40 FPGA. Measuring just 11.5 x 6 mm, the S1 is designed to be tiny both in footprint and power usage. 

Silicon Withchery S1

The module is perfectly suited for DSP and Edge-AI tasks running on battery power or in other low-power environments. According to the Silicon Witchery website It's available as a stand-alone module, or as one of two development kits. The first is the S1 popout board, which exposes all I/O as header pins, and StemmaQT/Qwiic connectors.

S1 dev kits

The second is an ECG Reference kit, featuring the S1 as part of a small 3-probe ECG measurement device. Reference for all three can be found on Silicon Witchery's documentation page. All three boards are available for $30, $39 and $45 respectively from Digikey, though at the time of writing, the S1 ECG KIT is not in stock.

Silicon Witchery S1: In Specifications


  • MCU: Nordic Semi nRF52840 Arm Cortex-M4 MCU @ 64 MHz with Bluetooth, Thread
  • FPGA: Lattice Semi iCE40 FPGA w/ 5K LUT and DSP blocks.
  • Storage: 32 Mbit Flash
  • Integrated antenna, passives, and crystals.
  • I/Os – 20x castellated holes w/:
    • 8x FPGA I/O include I3C, I2C, SPI, and USB.
    • 2x nRF GPIO pins with ADC and low power wake.
    • SWD debug pins
  • Power Supply
    • Lithium battery charging and monitoring
    • 3x adjustable Vout rails including 1x buck-boost up to 5.5V
  • Dimensions: 11.5 x 6 mm

BLE and FPGA in One Mini Package

The S1 is a wonderful piece of kit, combining bleeding edge technologies into a tiny, cheap, low-power package. If you've already spent some time with an nRF52840 development kit you'll find it much easier to get started as the Silicon Witchery SDK is based on the Nordic SDK. 

As for FPGA programming, that's a whole new skill to learn, but with USB port-sized dev boards like FOMU out there, there's never been a better time to start. You could even go super bleeding edge and learn RISC-V on an FPGA dev board.

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