Thunderboard Wear is a $75 Smartwatch Development Board by Silicon Labs

A few days ago I watched an’s video about an ARM’s smartwatch reference design running mbed OS 3.0, powered by a Silicon Labs EFM32 Giant Gecko Cortex M3 MCU, and promising up to 2 months battery life on a 160 mAh battery. While I could not find the full details about the reference design, I noticed Silicon Labs also launched a development board called Thunderboard Wear, based on the same platform, just quite bigger, and still wearable… (Sort of)

Thunderboard_WearThunderboard Wear specifications:

  • MCU – Silicon Labs EFM32GG995F1024 ARM Cortex-M3 MCU up to 48 MHz with 128 kB RAM,1 MB Flash
  • External Memory – 256 kB external SRAM
  • External Storage – micro SD card slot
  • Display – 128×128 pixel Memory LCD from Sharp
  • Connectivity – Bluetooth 4.1 smart module (Silicon Labs BGM111), upgradeable to Bluetooth 4.2
  • Sensors
    • Ambient Light Sensing (ALS) and Proximity/Gesture via Silicon Labs Si1141.
    • Optical hear-rate monitoring (HRM) via Silicon Labs Si1144
    • 9-axis accel/gyro/magnetometer Bosch
  • USB – 2x micro USB port (device and debug)
  • Debugging
    • Built in debugger with virtual COM port
    • Support for EFM32 STK debugger
  • Misc – Touch button and touch slider, user buttons, vibration motor for tactile feedback
  • Power Supply – Coin-cell battery, USB, or external power source.
  • Dimensions – N/A
Block Diagram
Block Diagram

EFM32 STK debugger (not included) allows for advanced/precise energy monitoring, and full ETM trace. The platform also support mbed Online IDE exports for Simplicity Studio available for Windows, Mac OS X, and Linux. Source code is available on

Thunderboard Wear evaluation board ships with an adjustable strap, ribbon cables for energy monitoring, and quick start guide.

The first 1,000 boards can be pre-ordered on Element14 for a discounted price. Price is $75 in the US, but will vary by depending on the country where the kit is purchased. More details may be available on Silicon labs’ Thunderboard Wear product page.

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