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.
Smart ARM power
Sensor Watch is powered by the Microchip SAM L22, an ARM Cortex M0+ microcontroller with tons of powerful peripherals.
Sensor Watch sips single-digit microamperes of power, making this a watch you can wear all year on a single coin cell.
A highly accurate 32.768 KHz crystal keeps accurate time — and displays it on the original F-91W LCD for a classic look and feel.
Light and sound
The LED backlight supports shades of red, green and yellow. With light soldering, you can also use the F-91W’s piezo buzzer.
A 9-pin connector breaks out an I²C bus and five GPIO for SPI, UART or analog input, letting you add sensors to Sensor Watch.
Fully open source hardware and software allow you to buy one or build your own — and remix the firmware to suit your taste.
Join the Sensor Watch Discord!
Chat with other Sensor Watch users and get help with your own Sensor Watch build.
We do a Pull Request contributions workflow on GitHub. New users are always welcome!
Follow along on Twitter!
Get the absolute latest from the developer of Sensor Watch, plus other posts.