About Sensor Watch

An ARM Cortex M0+ board swap for the classic Casio F-91W wristwatch.

Sensor Watch is a board replacement for the classic Casio F-91W wristwatch. It is powered by a Microchip SAM L22 microcontroller with built-in segment LCD controller. You can write your own programs for the watch using the provided watch library, program the watch over USB using the built-in UF2 bootloader, and then install the board in your existing watch case to run your own software on your wrist.

Serving Suggestion:

Photo: a close-up of the Sensor Watch circuit board, and a wristwatch displaying the word “Hello”


  • ARM Cortex M0+ microcontroller
  • 32KHz crystal for real-time clock with alarm function
  • Ten digit segment LCD, plus five indicator segments
  • Three interrupt capable buttons
  • Red / green PWM’able LED backlight
  • Optional piezo buzzer (requires some light soldering)
  • On-board USB Micro B connector
  • Reset button with double-tap UF2 bootloader
  • Nine-pin flex PCB connector