bluetooth

571 Articles

[Ben] at workbench with 3D-printed sea scooter

Watertight And Wireless In One Go: The DIY Sea Scooter

August 11, 2025 by 23 Comments

To every gadget, tool, or toy, you can reasonably think: ‘Sure I could buy this… but can I make it myself?’ And that’s where [Ben] decided he could, and got to work. On a sea scooter, to be exact.

This sea scooter was to be a fully waterproof, hermetically sealed 3D-printed underwater personal propulsion device, with the extreme constraint that the entire hull and mechanical interfaces are printed in one go. No post-printing holes for shafts, connectors, or seals. It also meant [Ben] needed to embed all electronics, motor, magnetic gearbox, custom battery pack, wireless charging, and non-contact magnetic control system inside the print during the actual print process.

As [Ben] explains, both Bluetooth and WiFi ranges are laughable once underwater. He elegantly solves this with a reed-switch-based magnetic control system. The non-contact magnetic drive avoids shaft penetrations entirely. Power comes from a custom 8S LiFePO₄ pack, charged wirelessly through the hull. Lastly, everything’s wrapped in epoxy to make it as watertight as a real submarine.

The whole trick of ‘print-in-place’ is that [Ben] pauses the builder mid-print, and drops in each subsystem like a secret ingredient. Continuing, he tweaks the printer’s Z-offset, and onwards it goes. It’s tense, high-stakes work; a 14-hour print where one nozzle crash means binning hundreds of dollars’ worth of embedded components.

Still, [Ben] took the chance, and delivered a cool, fully packed and fully working sea scooter. Comment below to discuss the possibilities of building one yourself.

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When Wireless MIDI Has Latency, A Hardwired Solution Saves The Day

June 7, 2025 by 14 Comments

[Moby Pixel] wanted to build a fun MIDI controller. In the end, he didn’t build it just once, but twice—with the aim of finding out which microcontroller was most fit for this musical purpose. Pitted against each other? The ESP32 and Raspberry Pi Pico.

The MIDI controller itself is quite fetching. It’s built with a 4 x 4 array of arcade buttons to act as triggers for MIDI notes or events. They’re assembled in a nice wooden case with a lovely graphic wrap on it. The buttons themselves are wired to a microcontroller, which is then responsible for sending MIDI data to other devices.

At this point, the project diverges. Originally, [Moby Pixel] set the device up to work with an ESP32 using wireless MIDI over Bluetooth. However, he soon found a problem. Musical performance is all about timing, and the ESP32 setup was struggling with intermittent latency spikes that would ruin the performance. Enter the Raspberry Pi Pico using MIDI over USB. The hardwired solution eliminated the latency problems and made the controller far more satisfying to use.

There may be solutions to the latency issue with the wireless ESP32 setup, be they in code, hardware configuration, or otherwise. But if you want to play with the most accuracy and the minimum fuss, you’ll probably prefer the hardwired setup.

Latency is a vibe killer in music as we’ve explored previously.

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The Brymen BM788BT shown along side other digital multimeters.

New Brymen Bluetooth BM788BT Digital Multimeter Coming Soon

April 15, 2025 by 14 Comments

If you’re into electronics you can never have too many digital multimeters (DMMs). They all have different features, and if you want to make multiple measurements simultaneously, it can pay to have a few. Over on his video blog [joe smith] reviews the new Brymen BM788BT, which is a new entry into the Bluetooth logging meter category.

This is a two-part series: in the first he runs the meter through its measurement paces, and in the second he looks at the Bluetooth software interface. And when we say “new” meter, we mean brand new, this is a review unit that you can’t yet get in stores.

According to a post on the EEVblog, this Bluetooth variant was promised five years ago, and back then Brymen even had the Bluetooth module pin header on the PCB, but it has taken a long time to get the feature right. If you scroll through the thread you will find that Brymen has made its protocol specification available for the BM780 series meters.

It looks like some Bluetooth hacking might be required to get the best out of this meter. Of course we’re no strangers to hacking DMMs around here. We’ve taken on the Fluke 77 for example, and these DMM tweezers.

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Better Bearings Take The Wobble Out Of Premium Scroll Wheel

April 9, 2025 by 12 Comments

Sitting in front of a computer all day isn’t exactly what the firmware between our ears was tuned to do. We’re supposed to be hunting and gathering, not hunting and pecking. So anything that makes the computing experience a little more pleasurable is probably worth the effort, and this premium wireless scroll wheel certainly seems to fit that bill.

If this input device seems familiar, that’s because we featured [Engineer Bo]’s first take on this back at the end of 2024. That version took a lot of work to get right, and while it delivered high-resolution scrolling with a premium look and feel, [Bo] just wasn’t quite satisfied with the results. There were also a few minor quibbles, such as making the power switch a little more user-friendly and optimizing battery life, but the main problem was the one that we admit would have driven us crazy, too: the wobbling scroll wheel.

[Bo]’s first approach to the wobble problem was to fit a larger diameter bearing under the scroll wheel. That worked, but at the expense of eliminating the satisfying fidget-spinner action of the original — not acceptable. Different bearings yielded the same result until [Bo] hit on the perfect solution: a large-diameter ceramic bearing that eliminated the wobble while delivering the tactile flywheel experience.

The larger bearing left more room inside for the redesigned PCB and a lower-profile, machined aluminum wheel. [Bo] also had a polycarbonate wheel made, which looks great as is but would really be cool with internal LEDs — at the cost of battery life, of course. He’s also got plans for a wheel machined from wood, which we’ll eagerly await.

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The ESP32 Bluetooth Backdoor That Wasn’t

March 10, 2025 by 40 Comments

Recently there was a panicked scrambling after the announcement by [Tarlogic] of a ‘backdoor’ found in Espressif’s popular ESP32 MCUs. Specifically a backdoor on  the Bluetooth side that would give a lot of control over the system to any attacker. As [Xeno Kovah] explains, much about these claims is exaggerated, and calling it a ‘backdoor’ is far beyond the scope of what was actually discovered.

To summarize the original findings, the researchers found a number of vendor-specific commands (VSCs) in the (publicly available) ESP32 ROM that can be sent via the host-controller interface (HCI) between the software and the Bluetooth PHY. They found that these VSCs could do things like writing and reading the firmware in the PHY, as well as send low-level packets.

The thing about VSCs is of course that these are a standard feature with Bluetooth controllers, with each manufacturer implementing a range of these for use with their own software SDK. These VSCs allow for updating firmware, report temperatures and features like debugging, and are generally documented (except for Broadcom).

Effectively, [Xeno] makes the point that VSCs are a standard feature in Bluetooth controllers, which – like most features – can also be abused. [Tarlogic] has since updated their article as well to distance themselves from the ‘backdoor’ term and instead want to call these VSCs a ‘hidden feature’. That said, if these VSCs in ESP32 chips are a security risk, then as [Xeno] duly notes, millions of BT controllers from Texas Instruments, Broadcom and others with similar VSCs would similarly be a security risk.

An image showing an original grey and blue Sony Walkman with the text "1970" below it, and an arrow pointing to the right of it at a much smaller blue Walkman with the text "2000" underneath it, and a final arrow pointing to the right to a bright orange cassette player by We Are Rewind in a man's hand with the text "now" beneath it.

Why Are Cassette And CD Players So Big Now?

March 1, 2025 by 65 Comments

The early 2000s were the halcyon days of physical media. While not as svelte as MP3 players became, why are those early 2000s machines smaller than all the new models popping up amidst the retro audio craze?

We’ve bemoaned the end of the electromechanical era before, and the Verge recently interviewed the people at We Are Rewind and Filo to get the skinny on just why these newer cassette and CD players aren’t as small as their predecessors. It turns out that all currently produced cassette players use the same mechanism with some small tweaks in materials (like metal flywheels in these higher quality models) because the engineering required to design a smaller and better sounding alternative isn’t warranted by the niche nature of the cassette resurgence.

A similar fate has befallen the laser head of CD mechanisms, which is why we don’t have those smooth, rounded players anymore. Economies of scale in the early 2000s mean that even a cheap player from that era can outperform a lot of the newer ones, although you won’t have newer features like Bluetooth to scandalize your audiophile friends. A new Minidisc player is certainly out of the question, although production of discs only ended this February.

If you’re looking to get back into cassettes, this masterclass is a good place to start. If you don’t fancy any of the players the Verge looked at, how about rolling your own incarnation with the guts from a vintage machine or just going for the aesthetic if cassettes aren’t your jam?

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Game Bub Plays ROMs And Cartridges

February 15, 2025 by 10 Comments

With today’s technology, emulating video game consoles from the 90s or before is trivial. A Raspberry Pi and a controller of some sort is perhaps the easiest and simplest way to go to get this job done, but to really impress the masses some extra effort is required. This handheld from [Eli] called the Game Bub not only nails the appearance and feel of the first three generations of Nintendo handhelds but, thanks to its FPGA, can play not only ROMs but the original game cartridges as well.

As [Eli] notes, the FPGA is not strictly necessary for emulation, but does seem to be better at interfacing with physical hardware like controllers and game cartridges. For this task an Xilinx XC7A100T with integrated memory was chosen, with a custom PCB supporting the built-in controller, speaker, a rechargeable lithium battery, and a 480×320 display (that had to be rotated out of portrait mode). An SD Card reader is included for any ROM files, and there’s also a ESP32-S3 included to give the handheld WiFi and Bluetooth capabilities, with future plans to support the communications protocol used by the Game Boy Advance Wireless Adapter.

There are a few other features with the Game Bub as well, including the ability to use an authentic link cable to communicate with the original Game Boy and Game Boy Color, and a Switch-like dock that allows the Game Bub to be connected to an external monitor. It’s also open source, which makes it an even more impressive build. Presumably it doesn’t include the native ability to dump cartridges to ROM files but you don’t need much more than a link cable to do that if you need to build your ROM library.

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