PJON, Open Single-Wire Bus Protocol, Goes Verilog

December 13, 2025 by Arya Voronova No comments

Did OneWire of DS18B20 sensor fame ever fascinate you in its single-data-line simplicity? If so, then you’ll like PJON (Padded Jittering Operative Network) – a single-wire-compatible protocol for up to 255 devices. One disadvantage is that you need to check up on the bus pretty often, trading hardware complexity for software complexity. Now, this is no longer something for the gate wielders of us to worry about – [Giovanni] tells us that there’s a hardware implementation of PJDL (Padded Jittering Data Link), a PJON-based bus.

This implementation is written in Verilog, and allows you to offload a lot of your low-level PJDL tasks, essentially, giving you a PJDL peripheral for all your inter-processor communication needs. Oh, and as [Giovanni] says, this module has recently been taped out as part of the CROC chip project, an educational SoC project. What’s not to love?

PJON is a fun protocol, soon to be a decade old. We’ve previously covered [Giovanni] use PJON to establish a data link through a pair of LEDs, and it’s nice to see this nifty small-footprint protocol gain that much more of a foothold, now, in our hardware-level projects.

We thank [Giovanni Blu Mitolo] for sharing this with us!

The Near Space Adventures Of Bradfield The Bear

December 12, 2025 by Al Williams No comments

Admit it or not, you probably have a teddy bear somewhere in your past that you were — or maybe are — fond of. Not to disparage your bear, but we think Bradfield might have had a bigger adventure than yours has. Bradfield was launched in November on a high-altitude balloon by Year 7 and 8 students at Walhampton School in the UK in connection with Southampton University. Dressed in a school uniform, he was supposed to ride to near space, but ran into some turbulence. The BBC reported that poor Bradfield couldn’t hold on any longer and fell from around 17 miles up. The poor bear looked fairly calm for being so high up.

A camera recorded the unfortunate stuffed animal’s plight. Apparently, a companion plushie, Bill the Badger (the Badger being the Southampton mascot), successfully completed the journey, returning to Earth with a parachute.

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Super-Sizing Insects And The Benefits Of Bones

December 12, 2025 by Maya Posch 9 Comments

One swol mealworm amidst its weaker brethren. (Credit: The Thought Emporium, YouTube)

Have you ever found yourself looking at the insects of the Paleozoic era, including the dragonfly Meganeuropsis permiana with its 71 cm wingspan and wondered what it would be like to have one as a pet? If so, you’re in luck because the mad lads over at [The Thought Emporium] have done a lot of the legwork already to grow your own raven-sized moths and more. As it turns out, all it takes is hijacking the chemical signals that control the development phases, to grow positively humongous mealworms and friends.

The growth process of the juveniles, such as mealworms – the larval form of the yellow mealworm beetle – goes through a number of molting stages (instars), with the insect juvenile hormone levels staying high until it is time for the final molt and transformation into a pupa from which the adult form emerges. The pyriproxyfen insecticide is a juvenile hormone analog that prevents this event. Although at high doses larvae perish, the video demonstrates that lower doses work to merely inhibit the final molt.

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Liberating AirPods With Bluetooth Spoofing

December 12, 2025 by Aaron Beckendorf 3 Comments

Apple’s AirPods can pair with their competitors’ devices and work as basic Bluetooth earbuds, but to no one’s surprise most of their really interesting features are reserved for Apple devices. What is surprising, though, is that simple Bluetooth device ID spoofing unlocks these features, a fact which [Kavish Devar] took advantage of to write LibrePods, an AirPods controller app for Android and Linux.

In particular, LibrePods lets you control noise reduction modes, use ear detection to pause and unpause audio, detect head gestures, reduce volume when the AirPods detect you’re speaking, work as configurable hearing aids, connect to two devices simultaneously, and configure a few other settings. The app needs an audiogram to let them work as hearing aids, and you’ll need an existing audiogram – creating an audiogram requires too much precision. Of particular interest to hackers, the app has a debug mode to send raw Bluetooth packets to the AirPods. Unfortunately, a bug in the Android Bluetooth stack means that LibrePods requires root on most devices.

This isn’t the first time we’ve seen a hack enable hearing aid functionality without official Apple approval. However, while we have some people alter the hardware, AirPorts can’t really be called hacker- or repair-friendly.

Thanks to [spiralbrain] for the tip!

Hidden Camera Build Proves You Can’t Trust Walnuts

December 12, 2025 by Lewin Day 7 Comments

Typically, if you happened across a walnut lying about, you might consider eating it or throwing it to a friendly squirrel. However, as [Penguin DIY] demonstrates, it’s perfectly possible to turn the humble nut into a clandestine surveillance device. It turns out the walnut worriers were right all along.

The build starts by splitting and hollowing out the walnut. From there, small holes are machined into the mating faces of the walnut, into which [Penguin DIY] glues small neodymium magnets. These allow the walnut to be opened and snapped shut as desired, while remaining indistinguishable from a regular walnut at a distance.

The walnut shell is loaded with nine tiny lithium-polymer cells, for a total of 270 mAh of battery capacity at 3.7 volts. Charging the cells is achieved via a deadbugged TP4056 charge module to save space, with power supplied via a USB C port. Holes are machined in the walnut shell for the USB C port as well as the camera lens, though one imagines the former could have been hidden purely inside for a stealthier look. The camera itself appears to be an all-in-one module with a transmitter built in, with the antenna installed in the top half of the walnut shell and connected via pogo pins. The video signal can be picked up at a distance via a receiver hooked up to a smart phone. No word on longevity, but the included batteries would probably provide an hour or two of transmission over short ranges if you’re lucky.

If you have a walnut tree in your backyard, please do not email us about your conspiracy theories that they are watching you. We get those more than you might think, and they are always upsetting to read. If, however, you’re interested in surveillance devices, we’ve featured projects built for detecting them before with varying levels of success. Video after the break.

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Rats Get Even Better At Playing DOOM

December 12, 2025 by Ian Bos 13 Comments

We all know that you can play DOOM on nearly anything, but what about the lesser known work being done to let other species get in on the action? For ages now, our rodent friends haven’t been able to play the 1993 masterpiece, but [Viktor Tóth] and colleagues have been working hard to fix this unfortunate oversight.

If you’ve got the feeling this isn’t the first time you’ve read about rats attempting to slay demons, it’s probably because [Victor] has been working on this mission for years now — with a previous attempt succeeding in allowing rats to navigate the DOOM landscape. Getting the rodents to actually play through the game properly has proved slightly more difficult, however.

Improving on the previous attempt, V2 has the capability to allow rats to traverse through levels, be immersed in the virtual world with a panoramic screen, and take out enemies. Rewards are given to successful behaviors in the form of sugar water through a solenoid powered dispenser.

While this current system looks promising, the rats haven’t gotten too far though the game due to time constraints. But they’ve managed to travel through the levels and shoot, which is still pretty impressive for rodents.

DOOM has been an indicator of just how far we can take technology for decades. While this particular project has taken the meme into a slightly different direction, there are always surprises. You can even play DOOM in KiCad when you’re tired of using it to design PCBs.

Review: Cherry G84-4100 Keyboard

December 12, 2025 by Jenny List 18 Comments

The choice of a good keyboard is something which consumes a lot of time for many Hackaday readers, judging by the number of custom input device projects which make it to these pages. I live by my keyboard as a writer, but I have to admit that I’ve never joined in on the special keyboard front; for me it’s been a peripheral rather than an obsession. But I’m hard on keyboards, I type enough that I wear them out. For the last five years my Hackaday articles have come via a USB Thinkpad keyboard complete with the little red stick pointing device, but its keys have started parting company with their switches so it’s time for a replacement.

I Don’t Want The Blackpool Illuminations

A picture of the Blackpool illuminations at night against a dark sky. — Is it a gamer’s keyboard, or the Blackpool seafront at night? I can’t tell any more. Mark S Jobling, Public domain.

For a non keyboard savant peering over the edge, this can be a confusing choice. There’s much obsessing about different types of mechanical switch, and for some reason I can’t quite fathom, an unreasonable number of LEDs.

I don’t want my keyboard to look like the Blackpool Illuminations (translation for Americans: Las Vegas strip), I just want to type on the damn thing. More to the point, many of these “special” keyboards carry prices out of proportion to their utility, and it’s hard to escape the feeling that like the thousand quid stereo the spotty kid puts in his Opel Corsa, you’re being asked to pay just for bragging rights.

Narrowing down my needs then, I don’t need any gimmicks, I just need a small footprint keyboard that’s mechanically robust enough to survive years of my bashing out Hackaday articles on it. I’m prepared to pay good money for that.

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