ESP32 Music Sequencer Is Clearly Nailing The Y2K Aesthetic

August 15, 2026 by Tyler August 2 Comments

Do you remember back when electronics came in clear cases? Back around the turn of the millennium, when translucency was chic. [3DSage] sure does, which is why he went to great lengths to make a clear case for his Clear Retro Music Sequencer.

The sequencer itself is based around an ESP32-S3 module with a built-in display, and a rotary encoder that handles most of the input. Most, because there’s a second button and a stylophone-like array of brass rods on one edge of the custom PCB he made with his fiber laser that can also handle note input. Other notable features include a phono jack with built-in switching so the tunes come out automatically from headphones or the internal speaker, and a AAA battery-lookalike. It’s a small detail, but that 666 mWh 3.7 V lithium cell is the demon’s meow for this project, seeing as it gives the convenience of a modern battery without compromising that Y2K look — remember you can see the battery through the translucent case.

About that translucent case: it’s 3D printed out of PETG, with settings similar to those we’ve reported on before: hot, slow, and don’t cross the streams! Which is to say every layer must line up with the one above. Oh, use filament fresh out of the drier of you live somewhere as humid as [3DSage]. The result is not totally see-through, but an application of clear enamel fills in the surface well enough to read through, giving the vintage look [3DSage] was after. To complete that Y2K feel, he turns the device into a slap bracelet, because why not? For those of you who missed due to the aforementioned federal prison arc, slap-on wristbands were all the rage amongst the kids back in those days.

The wristband is a length of measuring tape at its core, the springy steel having been cold-worked to hold the radius of [3DSage]’s wrist in its relaxed state, encapsulated in clear gorilla tape for comfort. We probably don’t have to tell you that getting slapped with a raw tape measure isn’t the nicest. For the actual operation of the sequencer, check out the video embedded below — the first 9 minutes cover the build, while the rest shows off the product.

Of course you don’t need an ESP32 for this kind of music maker– you can do it with a C64, or even discrete parts and rope-core memory.

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Making A Locked Down Wearable Work Without A Subscription

July 15, 2026 by Fenix Guthrie 13 Comments

WHOOP does not have the presence in the wearable space as other brands, but in certain circles, it’s a household name. Their business model requires you to have a yearly app subscription to use their fitness tracker, but here at Hackaday, we are big fans of actually owning the devices you buy — which is why we were happy to hear about an open source and subscription free WHOOP compatible app!

The goal of the so-called OpenStrap project is not to re-create the WHOOP app. Rather, the algorithms and processing methods are developed from scratch, based on public research. It’s all calculated locally on a 1 Hz interval, based on the data the WHOOP 4.0 device feeds the app. As such, the health data collected from the watch, never leaves the phone. While not the main goal of the project, the privacy improvement of the app’s serverless nature cannot be overstated. However, to display metrics, you first need to get data off the WHOOP to begin with.

The crux of the issue with making the WHOOP 4.0 work without the official app is the reliance on proprietary Bluetooth protocols. Fortunately, the protocol itself ended up being relatively simple. The WHOOP 4.0 amounts to little more than a series of sensors that sit on the user’s wrist. As such, the app can subscribe to the Bluetooth feed and decode the data, right? Well, the devil is always in the details with such things, and the protocol came with its fair share of quirks. The hardware clock needs to be synchronized, or it simply defaults to zero Unix time. Moreover, the analog sensors like, ambient temperature are given in relative ADC values, and are not terribly useful without calibration. Regardless, the result of the reverse engineering effort speaks for itself with the OpenStrap app able to recreate much of the functionality in WHOOP’s official app.

Quite often, devices reliant on proprietary apps are little more than manufactured e-waste. While we don’t expect many of you to actually own a WHOOP 4.0, we do hope to see the OpenStrap project keep at least a few out of the landfill in the future.

Speak Silently With An Ultrasound Probe

July 12, 2026 by Donald Papp 14 Comments

Speaking is much faster than typing, and while it’s an increasingly convenient way to interact with computers, it’s hardly private. Providing speech privacy in a way we haven’t seen before is this prototype tongue-reading system that uses machine learning and ultrasound to read tongue movements and turn them into decoded speech. Not only can a user speak without emitting a sound, since it doesn’t read sound waves it’s completely immune to noisy environments.

Tongues are a far richer source of speech data than reading lip and mouth movements.

It turns out that tongue movements are a very rich source of information about speech, and an ultrasound probe under the chin takes very clear video of a tongue. With a dataset consisting of only around 50 hours of training data, the system has a 15.6% error rate and generalizes across different speakers (as long as they speak with similar accents).

That error rate may seem high at first glance, but keep in mind this is for a prototype system built in a month around a relatively small training dataset. All indications are that better results are just a matter of better training.

Probably the biggest drawback at the moment is the size of the ultrasound probe and the way it must be held under one’s chin like a contact microphone, but at the moment the probe is an off-the-shelf model that is hardly optimized for either size, weight, or wearability. If the system seems promising enough, a probe resembling an adhesive patch might even be possible.

It’s certainly a different approach from others we’ve seen in the past, including whispering while inhaling and reading lip and mouth movements.

A Custom PCB For The Casio G-Shock

June 23, 2026 by Tom Nardi 13 Comments

With the PCB fabrication services available to the modern hobbyist, it’s become increasingly common to see replacement boards designed for all sorts of devices. Even so, it’s sometimes still a little difficult to believe that we’re at the point where hardware hackers are now producing advanced replacement PCBs for commercial wristwatches such as this drop-in upgrade for the iconic Casio G-Shock by [David Volovskiy].

Honestly, we’d have been impressed if the thing could just tell the time. But the replacement board combined with the open source firmware brings new capabilities that far exceed anything the G-Shock was capable of originally. The upgraded watch now offers several applications, such as a pedometer and a number of games including simplified versions of Blackjack and Wordle. The watch can tell you the phase of the Moon, calculate sunrise and sunset, and display values pulled from the internal thermometer.

Even if you don’t have a G-Shock in need of a new PCB, [David] has put together a web-based emulator that lets you play around with the firmware. The online tool that lets you visualize how the watch’s LCD is mapped is also very slick. For those interested in getting a board of their own, you can join the project’s Discord server and get your name on the list for an upcoming production run.

If some of this sounds familiar, it’s because [David] based his project on [Joey Castillo]’s Sensor Watch, which is a replacement PCB for the Casio F-91W. With these two projects available for others to build from, one wonders how many other Casio watches might get their own upgraded hardware in the future.

The Repair Nightmare That Are Smart Rings

June 20, 2026 by Maya Posch 21 Comments

In the quest to make every wearable device ‘smart’, a lot of electronics along have to be crammed in very small spaces, along with ways to make them resistant to environments that our bodies do not mind, like getting hit by a rainstorm or simply washing our hands. These two factors combined make especially devices like smart rings an interesting case study for repairability, with [iFixit] recently taking apart a modern Oura smart ring to assess its e-waste factor after the built-in battery dies.

The tiny 10.5 mAh Lipo cell in the Oura Ring 5. (Credit: iFixit)

The subject of the teardown video is the Oura Ring 5, a $400 smart ring that’s designed to track your vitals much like a wrist-worn fitness tracker — just in a much smaller package. This metal-and-epoxy sandwich can definitely survive a good rain shower and washing of hands, but to get to the internals rather forceful methods were needed, unlike previous Oura and Samsung smart rings where some applied heat was enough.

In the Ring 5’s case even more heat was needed to make the inner ring start to slide out, but by that point the Li-ion battery inside had already popped from the heat. The inner ring then got stuck and more violence was required to continue the disassembly and get to the super-tiny, 10.5 mAh battery. Of course, at this point the smart ring really won’t be getting back together, never mind still work or be waterproof, which is a central issue with these smart rings.

With the EU’s February 2027 deadline for user-replaceable batteries looming on the horizon, it’ll be interesting to see whether devices like this can squeeze into an exception category, or whether manufacturers will have to massively redesign or stop selling these devices to this rather large market. So far this particular regulation has already forced Nintendo to make a special Switch 2 console for the EU.

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Custom Watch Is On The Case

June 13, 2026 by Al Williams 14 Comments

We were excited to see [Z0hn]’s project about 3D printing a custom watch from scratch — both because it was an exciting idea, and because the pictures looked great. While we still liked the project, we quickly realized it wasn’t really printing a watch so much as it was printing a case that holds an off-the-shelf movement. But it still looked great.

Many homebrew watches are cool and fine to wear to your next hackerspace board meeting. But this watch wouldn’t raise an eyebrow out among the normal public. Conventional watches use press-fit backs, tiny screws, or make the back screw into the housing. None of those are great for 3D printing, so this watch uses a bayonet connector, which is easy to create, robust, and reliable.

The watch looks easy to modify, so if you don’t like, for example, the unusual crown placement, you can change it. The movement is a Miyota 8N24 and, of course, the crystal is off-the-shelf, too.

While not exactly a printed watch, it was still pretty cool, and there are lessons to be learned here if you want to pull off the same feat. Or just go full on hacker. You could, too, try your hand with an open source movement.

After The Dust Settles: Building Pebble Apps

June 1, 2026 by Bryan Cockfield 17 Comments

For a piece of wearable technology, Pebble has had a fairly “rocky” history. One of the most successful Kickstarters of its era, it went on to get acquired by FitBit, quietly shelved by them, then acquired by Google and open-sourced, where it’s now somewhat back in the hands of its original creator. Its new open source nature means that regular people can develop for these popular watches again, and [Coconauts] have developed a guide for these watches, new and old.

The original watches had to be coded using C, which is a fundamental language but one that generally isn’t used much in the modern world outside of embedded systems and other areas where efficieny is important. C does much less hand-holding than modern languages, so there are a number of things to keep an eye on when coding for these watches that languages like Rust, Go, and Python handle on their own. Regardless, the two-person team recently built a pair of apps for the Pebble platform as part of an app-making contest, one which notifies the user that the watch is charged to 80%, and another that shows an interactive kitten on the watch’s face.

Both of the apps are available from the Pebble app repository, and from there the source code can be found on respective GitHub pages if you’re looking for some examples to dust off old C skills. If you happen to have an old Pebble watch or always wanted one but didn’t want to deal with FitBit, now might be a good time to get them out and start tinkering around with it since it’s now in the open-source domain.