Sensor Watch

A hackable ARM Cortex M0+ upgrade for a classic Casio wristwatch

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Aug 31, 2023

Project update 14 of 14

Sensor Watch Lite shipping soon — check your shipping details!

by Joey Castillo

Hi y’all! It’s been a minute since the last update. I’m going to put the big news right at the top: Sensor Watch Lite is in manufacturing even as we speak, and the first 500 boards will ship out to Mouser in the coming days. These 500 boards will fulfill everyone who preordered Sensor Watch Lite, so if that describes you, now would be a good time to double check your shipping address at Crowd Supply!

We had originally expected a ship date of August 31 for Sensor Watch Lite, and while we’re very nearly hitting that, you’ll probably end up getting your boards sometime in September instead. It’s been a rollercoaster of a year trying to get these boards made, not least because of echoes of the chip shortage. If you’ll recall, we placed our order for SAM L22 chips in January of this year and expected to take delivery of the chips in late May. Budgeting two to three months for manufacturing and a month for logistics felt conservative — but then when May rolled around, our reel of chips got delayed to November.

Now, I know what you’re thinking: “But Joey, it’s not November yet!” And yes, that is true. What happened next is I asked the good folks at Crowd Supply if it was possible to shake the chip tree, as it were, and see if they could get anything to fall out. They did just that: at a meeting with Microchip in May, Crowd Supply mentioned the plight of Sensor Watch Lite — and while we never got a formal reply, some weeks later, the chips’ ship date got quietly pulled back in from November to July.

Getting from chips in May to delivery in August felt conservative. Getting from chips in July to delivery in August turned out not to be possible. Still, we’re going to get you your Sensor Watch Lite boards in September. It’s an aggressive timeline that’s taken a coordinated effort from all of us — me and Objects, Crowd Supply and Mouser, and especially my manufacturing partner, Cyber City Circuits in Augusta — and I’m super proud to be putting this product in your hands and on your wrists next month.

Also, if you just can’t get enough Sensor Watch Lite, our manufacturing run got a shoutout in Adafruit’s Ask an Engineer live show last night! They even played some behind-the-scenes footage of the production line at Cyber City Circuits, including the battery of tests that each board goes through before it gets the thumbs-up.

New Features: It’s Red! (And More Accurate!)

Sensor Watch Lite brings a few changes from Sensor Watch Classic. As mentioned before, the design is streamlined a bit, integrating the temperature sensor into the board for a simpler user experience. I spent more time fine-tuning the crystal oscillator circuit, which should make the clock much more accurate. I also made a tweak to the LED driving circuit that makes the LED ever ever so slightly brighter. To make a long story short, you’ll need to download a different build of the firmware for these new boards, and I wanted to give you a visual indication of that fact.

So the boards are red now.

If you’ve ever downloaded a custom firmware build for Sensor Watch, you’ve already seen that the builds come in two different “flavors”: you can download the firmware for blue boards (the limited run Sensor Watch with red/blue LED) or for green boards (the traditional Sensor Watch). Soon a third link will join these two options: there will be a link to download firmware for red boards, which is what you’ll want for Sensor Watch Lite. The red boards (with a handsome gold plated finish) cost a little bit more, but I think it’s a nice affordance to make clear which version of the firmware you’ll need to download.

If you’re building your own custom firmware, building for the red boards is as simple as passing a flag to the make command. There are three members of the Sensor Watch family now, and you can build the same code for any of them with a simple compiler flag. (We’ll be updating the documentation shortly.)

Sensor Watch Lite firmware: bonus watch faces!

Your Sensor Watch Lite will ship with a build of Movement with five watch faces in rotation: you get the simple clock, the world clock, sunrise/sunset, moon phase and stopwatch. After that you also get the preferences and time set screens, which allow you to set preferences like LED color and, of course, the time and date.

I feel like this version of the firmware is packed with useful stuff — and yet, every board now ships with a temperature sensor, and this selection of watch faces doesn’t make use of it.

So there are also two bonus watch faces: temperature and battery voltage. They’re hidden away behind a long press of the Mode button on the first watch face, the simple clock. When you hold down the Mode button, you get the temperature watch face (Celsius by default; press the Alarm button to switch to Fahrenheit). Press Mode one more time to see your battery voltage. And then press Mode again to return to the standard rotation of watch faces.

This felt like a nice way to offer a little something extra, without cluttering up the main rotation with too many watch faces. In the future, I’d love to explore ways to add even more features like this to Movement, the community firmware for Sensor Watch. Speaking of which:

State of the Movement

Movement is now up to 41 contributors (and rising)! I’ve been behind on merging pull requests, but we’ve added (or will soon add) a bunch of new watch faces, including our first game (a higher/lower guessing game), a watch face for menstrual cycle tracking, a new style of decimal time, and a watch face based around the ancient western esoteric concept of Planetary Hours.

The one that blows my mind, though, is the new Wyoscan watch face by Willy Hardy. This watch face replicates the behavior of a 2014-era F-91W board swap that does a gorgeous sweep across the clock digits at a rate of once every two seconds. It’s likely to consume a lot more battery power compared to the traditional clock display, but my goodness it’s so pretty — check it out for yourself!

Also: that sticker on the front of the Sensor Watch in that video is a Sensor Watch Screen Thing, one of a sheet of stickers that let you dress your Sensor Watch in costume. You can pick up one of those at the link (and I hope to get them added to the Crowd Supply page at some point).

Anyway. That’s the state of play for Sensor Watch Lite. Thanks so much for being a part of this journey and I can’t wait to see what you all do with this new incarnation of Sensor Watch!

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