Oddly Specific Objects
Mobile Devices
Cyber City Circuits
Sensor Watch Pro
A more hackable ARM Cortex M0+ brain upgrade for Casio's iconic F-91W
Oddly Specific Objects
Mobile Devices
Cyber City Circuits
Sensor Watch is a modern hardware drop-in for the classic Casio watch. It takes an iconic 30-year-old design from a golden age of digital watches, and pairs it with a modern, powerful microcontroller. This small circuit board, less than an inch in diameter, replaces the original quartz movement in a Casio F-91W or A158W watch to put the capabilities of an ultra-low-power ARM Cortex M0+ microcontroller on your wrist.
Sensor Watch Pro is the most advanced version of Sensor Watch yet. In addition to its 9-pin connector for interfacing with external sensor boards (like the optional accelerometer board add-on), it adds an RGB LED, an infrared light sensor, a voltage boost for the piezo buzzer for extra volume, and a soldering-free installation experience. It’s also, as a watch, extremely accurate thanks to its software-defined temperature compensation; with fine tuning, Sensor Watch Pro can drift less than a second per year.
It also looks hella cool with its swirly, visible traces shining through its transparent soldermask.
Sensor Watch is not like most smart watches. It makes a different set of engineering tradeoffs, to achieve a different set of goals:
Two major shortcomings of the classic Sensor Watch Lite board were the low volume of the beepy piezo buzzer, and the need to de-solder and re-solder a fiddly metal part from the donor Casio’s circuit board. Now, with some heroic parts sourcing, we’re able to solve both of those problems.
First, a tiny 14,000 µH inductor — the tiniest we were able to find — now boosts the voltage going to the buzzer, just like in the original Casio watch. This makes the beep of the buzzer significantly louder: plenty loud to function as an alarm or countdown timer.
In fact, it’s so much louder that we’re adding a new feature to the watch library: volume control, which will let you beep Sensor Watch Pro at max volume or a little softer, depending on context or preference.
We’ve also had a custom-fabricated metal spring connector manufactured, matching the precise size and shape of the part you previously had to solder yourself. This connector will be pre-soldered into place before shipping, meaning you just have to swap the board. No soldering required! Streamlining this piece of the process — and delivering the louder volume that so many people wanted — was a major goal for Sensor Watch Pro.
But we’re just getting started.
For Sensor Watch Pro, we’ve upgraded the LED that powers the backlight, bringing back shades of blue for the first time since the blue Limited Edition boards. Sensor Watch Pro sports a red, green AND blue LED, which can backlight your watch in all the colors of the rainbow.
What’s more: in addition to these three channels of light output, Sensor Watch Pro adds, for the first time, a channel of light input! An infrared phototransistor behind the transflective LCD allows you to sense light levels, even when the watch remains fully sealed.
In addition to functioning as an analog input for sensing light levels, this phototransistor is also tied to one of the SAM L22’s SERCOM peripherals, which we hope to leverage for data transfer functionality in the future.
The original promise of Sensor Watch was a modular system for adding different kinds of sensors to Sensor Watch. Now for the first time, we’re offering a second sensor board here on Crowd Supply: an accelerometer add-on with the LIS2DW MEMS motion sensor.
This tiny MEMS sensor supports measurement ranges from ±2 g to ±16 g, and output data rates from 1.6 Hz to 1600 Hz with a 32-level FIFO (which lets you burst data 32 samples at a time). The sensor also offers two interrupt lines tied to two different timer/counter peripherals for low-power event counting. One interrupt line is also tied to an external wake pin, which can allow for fast wake from low energy mode on motion events.
These interrupts are highly configurable, but at a minimum, the accelerometer sensor can automatically wake the device when it detects:
This accelerometer sensor will add a ton of options for sensing motion and activity, and for creating new interaction models with the single- and double-tap events.
We’re also, for the first time, offering an optional custom LCD that extends the capabilities of the classic Casio F-91W.
This custom LCD extends the number of segments available: from 72 segments on the classic Casio F-91W, to 92 segments on this brand new display. Instead of two letters for the weekday, we now offer three, with more versatile options for displaying almost every letter of the alphabet. The two-digit date area now supports numbers from 0-99 (up from 39 on the original LCD), and the clock area now offers a decimal point and a leading 1, for displaying longitudes and temperatures above 100 degrees.
The seconds also support alphanumeric display, for displaying units (mi), directions (NW) or any other alphanumeric things you can display on the top row. We also used this opportunity to add some new indicators: a half-moon indicating sleep mode, a looped arrow indicating repeating or recurring item, and an icon indicating the need to change the battery.
The community Sensor Watch firmware (called Movement) has matured in leaps and bounds since the release of Sensor Watch and Sensor Watch Lite. The community has embraced and run with this firmware, developing dozens of new watch faces beyond the classic World Clock, Moon Phase and Sunrise/Sunset offered at launch.
Among these new additions are dozens of complications, utilities and games, as well as some watch faces that are just plain fun:
This is, of course, in addition to the classic Clock, Stopwatch and Alarm watch faces, as well as a plethora of other everyday additions:
These are just a few of the literally dozens of watch faces that the community has put forward. And with the community-powered Sensor Watch Builder, generating firmware has never been easier: you can select just the watch faces you want, select the options you want, and download a compiled UF2 file, ready to drag and drop onto the Sensor Watch board via USB.
Still, and perhaps most importantly: Sensor Watch is open source and easily hackable, which means you can code up any watch face that make sense for YOU. New features like the accelerometer sensor and infrared light sensor are going to open the door to all kinds of new applications and experiences on Sensor Watch, and I can’t wait to see what YOU want to see most on Sensor Watch.
The SAM L22 microcontroller at the heart of Sensor Watch is an ARM Cortex M0+ chip with 256 KB of Flash and 32 KB of RAM, running at up to 32 MHz. It’s similar in many ways to the SAM D21 you’d find in a Feather M0 or Arduino Zero, with many of the same versatile peripherals:
The 9-pin sensor board connector offers a lot of additional functionality that you can make use of on a sensor board:
| Sensor Watch Pro with Accelerometer and Custom LCD | Sensor Watch Lite | Casio F-91W | |
|---|---|---|---|
| Manufacturer | Oddly Specific Objects | Oddly Specific Objects | Casio |
| Watch Size (in case) | 34.5 mm × 37.5 mm × 8.5 mm | 34.5 mm × 37.5 mm × 8.5 mm | 34.5 mm × 37.5 mm × 8.5 mm |
| Water Resistance | 30 meters | 30 meters | 30 meters |
| Buttons | 3 | 3 | 3 |
| Sensors | Ambient light sensor, temperature sensor, modular 9-pin connector with I2C and five analog inputs or digital IO | Temperature sensor, exposed pads for two analog inputs or digital IO | None |
| Accelerometer | LIS2DW accelerometer with activity and tap recognition, and two external interrupt channels | No | No |
| Backlight | Customizable Red/Green/Blue LED | Customizable Red/Green LED | Dim green LED |
| Buzzer | Amplified piezo buzzer | Piezo buzzer | Amplified piezo buzzer |
| Programming Interface | Built-in USB | Built-in USB | None |
| Design Files Available | Yes | Yes | Abundantly No |
| Display | Low-power 92-segment LCD with improved icons and alphanumeric characters | Low-power 72-segment LCD | Low-power 72-segment LCD |
| Data Input | Infrared Sensor, UART test points | UART test points | None |
| Battery Life | 1-2 Years | 1-2 Years | 7 Years |
| Price | $79 | $58 | $19 |
Some parts for this campaign are already procured or in flight. We’ve secured 3,500 of our most crucial part, the tiny inductor for the voltage boost, on preorder from Mouser. The custom spring connector for the buzzer is in manufacturing with our sheet metal partner, Shenzhen Fulimei Technology Company, and final tooling samples of the custom LCDs are in flight with our LCD partner, Team Source Display. We’ve also received and validated our first test run of panels from PCBWay, using our final board parameters with their advanced PCB service.
When the campaign concludes, we plan to order final PCB panels from PCBWay and all remaining parts from Mouser. Our manufacturing partner, Cyber City Circuits in Augusta, Georgia, is ready to assemble, test, pack and ship these boards, including hand-soldering each of the spring connectors to ensure that you have a solder-free, ready-to-swap board for the Casio wristwatch you’ll soon turn into a Sensor Watch Pro.
As soon as all the boards are assembled and tested, we will ship them to Mouser Electronics, Crowd Supply’s fulfillment partner, who will distribute them to backers. You can learn more about Crowd Supply’s fulfillment service under Ordering, Paying, and Shipping in their guide.
At this time, we are still waiting to receive the final samples of the LCD and the spring contact, the two custom parts for this project. Both are scheduled for delivery in October. While we’ve made every effort to ensure that these parts are fully compatible with the board — and in the case of the LCD, we’ve even tested against two previous rounds of samples — an unexpected issue here could incur a delay.
We are also waiting on the inductor for the buzzer boost, which is on back-order; while this back-order promises to ship on November 1, a significant delay there could push manufacturing out beyond our expected timeline. We don’t expect this, but it is a risk.
Luckily, all our off-the-shelf parts are available in the quantities we need, with immediate shipping, and the global semiconductor shortage seems to have abated for the moment, so we hope to get Sensor Watch Pro manufactured very quickly after the close of the campaign!
"The product allows you to replace the watch’s quartz crystal with an ARM Cortex M0+ microcontroller. This brings Movement firmware with a wide range of features, including interval timers, Wordle and a TOTP Authenticator."
Produced by Oddly Specific Objects in Brooklyn, NY, USA.
Sold and shipped by Crowd Supply.
An even more hackable board swap for the classic Casio F-91W wristwatch
An accelerometer sensor add-on for classic Sensor Watch and Sensor Watch Pro
An LCD swap for all Sensor Watch boards with extra icons and improved capabilities
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