Sensor Watch Pro

A more hackable ARM Cortex M0+ brain upgrade for Casio's iconic F-91W

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Sep 25, 2024

Project update 1 of 3

At long last, the Sensor Watch Pro campaign is live!

by Joey Castillo

Hey there! Joey here. Thanks for signing up for the Sensor Watch Pro pre-launch mailing list; you are one of the true believers, and for that I’m truly grateful. I’m also truly stoked to be able to share this news, the news that you’ve been waiting for: Sensor Watch Pro is now live on Crowd Supply, and you can back now it to get one of your own! It’s the most powerful Sensor Watch board yet, and it sports a striking new look: transparent solder mask, that lets the boards curvy copper traces shine through:

If you’re at all familiar with the classic Sensor Watch project, I think that Sensor Watch Pro will feel like both a return to form, and a big leap forward. Sensor Watch Pro remains a board swap for the classic Casio F-91W (and A158) digital wristwatch, supercharging this iconic classic with a brainy ARM Cortex M0+ microcontroller — the Microchip SAM L22 — and a flexible accessory port for adding different kinds of sensors to the watch.

With Sensor Watch Pro we’re adding some big new on-board features, as well as a couple of accessories that elevate the Sensor Watch platform to new heights.

More Features, and a Streamlined Build

When building the original Sensor Watch, it felt ambitious to squeeze as many features as we did into such a small watch case. Now, with Sensor Watch Pro, we’re squeezing even more functionality into the same space: a louder piezo buzzer, RGB LED, on-board temperature and infrared light sensing, and that classic 9-pin sensor board connector with on-board I²C pull-ups.

We’ve also made it easier than ever to perform the board swap. In both the original Sensor Watch and Sensor Watch Lite, you had to de-solder a tiny metal part from the original Casio watch movement, and re-solder it to Sensor Watch. For Sensor Watch Pro, we’re having that spring connector custom-fabricated, and soldering it on for you.

When coupled with the new voltage boost circuit — which we’ll talk about more in a later update — Sensor Watch Pro offers the loudest buzzer experience yet, with no soldering required. All you need is a screwdriver.

The Accelerometer Sensor

A new Sensor Watch calls for a new sensor board, and with this campaign, we’re offering for the first time an accelerometer sensor board with the LIS2DW12!

This tiny MEMS sensor plugs into the 9-pin connector on Sensor Watch, and fits into the handful of cubic millimeters we left free in the watch case. It’s extremely configurable, offering acceleration sensing at a variety of ranges and data rates. We’ve also wired up the accelerometer’s two interrupt channels to pins on the sensor board; interrupt options include wake-up and orientation change as well as tap events and double-taps.

The accelerometer sensor is extremely low power, sipping just a few hundred nanoamperes in its lowest-power sensing mode, and just 1.2 microamperes when sampling at 12.5 Hz. We think this accelerometer sensor is going to open all kinds of new avenues for activity sensing, as well as new options for interaction in the form of tap and double-tap events.

The Custom LCD

But we didn’t stop there. For those who want to squeeze even more functionality into this tiny watch case, we had a custom LCD fabricated. This custom LCD is identical in size to the LCD in a classic Casio F-91W, but instead of sporting 72 segments, it sports 92!

This custom LCD adds several extra indicators, including a looping arrow, a half-moon for sleep mode, and an icon that indicates the need to change the battery. It also adds a third character to the weekday display — “MON” instead of “MO” — and dispenses with a lot of the fiddly limitations of the classic LCD. For good measure, we also added a downstroke to the last two digits on the clock — perfect for showing the “MI” in Miles, the “°W” in a longitude, or even an “AM” for times in the morning.

More to come!

I’m so thrilled to be sharing this launch announcement with y’all. Over the next few weeks, I’m looking forward to sharing even more about Sensor Watch: tales of prototyping and parts sourcing, new possibilities afforded by the upgraded board and the new accessories, and of course, updates on the state of Movement, the community firmware for Sensor Watch.

For now, I invite you to check out the campaign page and consider backing Sensor Watch Pro today!


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