Casio F-91W is a popular watch that was first released in 1989, and it is still sold today for around $15. The team at “Oddly Specific Objects” decided to create the “Sensor Watch” open-source hardware board based on Microchip SAM L22 Cortex-M0+ microcontroller that can replace the electronics inside the watch.
They still keep the display and enclosure and wristband from the original Casion F-91W watch, but the new board connects to a temperature sensor board, and more importantly, provides the ability to hack/program the watch with your own code, besides the few samples provided, or even design your own sensor board.
Sensor Watch board specifications:
- MCU – Microchip SAM L22 Arm Cortex M0+ microcontroller @ 32 MHz with 32KB RAM, 256 KB of Flash with up to 16 KB EEPROM emulation area
- Display – Controller for 10-digit segment LCD, plus five indicator segments
- USB – 1x Micro USB PCB connector
- Sensor – Thermistor for temperature sensing
- Expansion
- 9-pin flex PCB connector for sensor boards with I2C, 3.3V, 5x GPIO configurable as analog pins, SPI, UART, PWM, etc..
- Edge-plated contacts for 3x interrupt-capable buttons
- Connection pad for piezo buzzer (requires light soldering)
- Misc
- 32.768 kHz crystal for real-time clock functionality with alarm support
- Red & green PWM’able LED backlight (red & blue on limited-edition boards)
- Reset button with double-tap UF2 bootloader
- Battery – CR2016 coin cell good for about one year
- Dimensions – Fits into Casio F-19W watch
You’ll find the EAGLE schematics for the mainboard and several sensor boards, as well as C code samples on Github together with some basic documentation to get started. It’s difficult to compare the Sensor Watch with other hackable watches like PineTime or Watchy, since it lacks Bluetooth or WiFi connectivity and comes with a more basic display, but that gives it one clear advantage in terms of battery life, since it can last around a year instead of a few days or weeks per charge. Another advantage is the watch remains waterproof since the board does not add any external connectors.
The Sensor Wach board is now available on Crowd Supply for $35 with a $10,000 funding goal. There are two similar perks with a blue PCB variant expected to come out in April 2022, and a green PCB model slated for the end of September 2022. Shipping adds $8 to the US Shipping, and $18 to the rest of the world.
Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.
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Kinda cool, the F91W being waterproof / airtight makes sensors and battery charging difficult I suppose. Still, a chess AI in a Casio watch sounds interesting.
I forgot to write about that part. There’s no charging and the watch should remain waterproof. Sensors are inside the watch as well. That means something like a temperature sensor may have limited practical applications, unless SAM L22 runs really cool, which it might be..
If they are still getting a year of battery life out of a single CR2016 then it will be running at micro-Watts so will not heat up at all. (a stock F91W runs for 7 to 10 years)
looks mildly fun as a party gag with a retro touch, but not remotely fun enough nor enough fun for the cost (35$, let alone with added +18$ shipping +VAT, import duties and import handling fees +15$ for the F-91W)…
…especially given how limited this is compared to the much cheaper and more powerful watch hacks out there, with several hackable smart watches or fitness trackers with nRF52-based (or TLSR8232 if you want it even cheaper) SoC, graphic touch display and bluetooth
The CrowdSupply campaign for this board’s successor: Sensor Watch Pro:
…is now live!