Mysterious Files PH

Perhaps the most famous of all the software-defined radio (SDR) receivers is the RTL-SDR, a digital TV receiver on which an undocumented feature was found. Perhaps other radio-enabled chips also have the same undocumented feature? It seems in the case of some members of the ESP32 family, they do. It’s a discovery made independently in two places, by Espargos, and a Reddit user by the name of h0m3us3r.

What’s happening is that the undocumented mode taps the I/Q stream off before the WiFi modem, and this can be read and processed by SDR software on an external computer. The undocumented mode can be found on ESP32 chips with the earlier Tensilica hardware onwards, so the low power Bluetooth only chips or the non-radio-equipped P4 won’t work. Sadly it’s also only possible with the receive side, with both 2.4 and 5 GHz bands being supported depending on the microcontroller in question.

This isn’t quite the general purpose SDR we got with the RTL-SDR, but there are still plenty of uses to which it can be put. We’re curious as to whether someone can implement the software side of an SDR on the same chip, but we are guessing that might be beyond their capabilities. Either way, we’re looking forward to what the community does with this new-found knowledge.

While you may not be familiar with the term “busy board”, you’ve almost certainly seen one. It’s the sort of toy with a bunch of buttons, switches, and of course LEDs, that are designed to keep young children entertained. As it so buttons, switches, buttons, and LEDs also keep hardware hackers entertained — doubly so if they are the ones designing said busy board in the first place.

That’s where we find [Andy], or should we say, [Uncle Andrew]. Last Christmas he decided to scratch build an electronic busy board for his nephew, and while it might not be a terribly complex piece of kit from a technical standpoint, it’s a fantastic multidisciplinary project in that it’s really equal parts hardware and software. While it would surely be possible to implement a gadget like this entirely in hardware, [Andy] took the modern hobbyist approach of offloading some of the task to a collection of carefully arranged ones and zeros.

In the write-up, [Andy] goes over the decisions he made while designing and building the device. This ranges from the extra effort put in to keep the PCB down to two layers and the logic behind LED multiplexing. This extends right into the software aspect of the project, with a surprisingly deep explanation of how the code uses timers and interrupts to run the show as efficiently as possible, maximizing the run time of the PIC18F67K40 microcontroller on a trio of AAA batteries.

It’s a fun read about a low-stakes project that’s made all the better by the personal touch. Just like the kids of makers and hardware hackers, [Andy]’s nephew is a lucky to have somebody like this in his life.

Homebrew computers don’t have to be retrocomputers, but [Just4Fun]’s all-through-hole, 68008-based “68k-MBC” certainly qualifies, so it is a worthy entry in our ongoing contest. While there are both “full” and “lite” hardware configurations, the three-IC “lite” configuration is what first caught our eye. Yes, three: the 68008, an SRAM chip, and a PIC microcontroller that acts as the ROM.

Software is provided by the suitably-retro CP/M68K, or standalone executables, which run on both hardware configurations. The “lite” option restricts you to a maximum of 512 KB of RAM and a single serial port, but it looks like you still get I2C and the option to plug in an SD “hard drive” or RTC module however you configure the machine. Through the serial port, you can of course connect a terminal of you choice, or even use a thermal printer. The “full” version has two serial ports, if you want to do both. [Just4Fun] also has a parallel adapter lets you plug in printers with that interface as well. The demo video is below, but be warned that the text-to-speech narration won’t be to everyone’s liking.

We’ve featured other single-board-computers using the 68k before, but this one is a worthy contender in our contest, not least for the impressively low chip count. This contest has gotten oodles of entries, but there’s still time for yours: entries close October 27th.

Another all-European podcast for you this week, as Elliot Williams is joined by Jenny List for an evening looking at the past week in Hackaday. And this week there is a particularly good selection to look at.

A while back we showed you a project that put synthetic aperture radar on a drone, generating extremely detailed imaging of the terrain beneath it. This week we had an update, in which an ingenious positioning accuracy fix gave it an astonishing increase in resolution. On top of that project we have 3D lightfield image display with the unexpected help of a Nipkow mechanical TV scanning drum. Geting your own microprocessor manufactured, DOOM in a database server, and a comprehensive array of unusual sensors in a tricorder project complete the picture.

Finally we have a couple of space stories and Jenny describing the preserved industrial delights of the Ruhr valley in Germany. You’ll want to go there, but first you’ll want to listen to the podcast.

Download it yourself in MP3. It’s wafer thin.

Episode 389 Show Notes:

News:

• No More Windows For The Dutch Government, Ze Kiezen Nu Linux

Mailbag:

• Thanks [Jason] for your Mailbag theme music submission. The beatings will continue until morale improves.

Interesting Hacks of the Week:

• Synthetic Aperture Radar Drone Gets Interferometric Imaging
• You Can Make A Microprocessor That’s All Your Own
• Electromechanical TV Goes 3D With This Light-field Display
  • Mechanical Image Acquisition With A Nipkow Disc
  • GitHub – Jenny’s Nipkow disk and mirror drum code
• Abusing SQL To Play DOOM
• Open Source Tricorder Is In It For The Science
  • High Speed Imaging Of Magnetic Fields
  • Gamma Ray Spectroscopy The Pomelo Way

• The Whole Computer Is Vim
• Cheap Yellow Display Dreams Of PDA
• A JavaScript OS For The ESP32

Quick Hacks:

• Elliot’s Picks:
  • Sheety Turns Spreadsheets Into Binaries, For Some Reason
  • Pogo-Bot Goes All Terrain With Compliant Foot
  • Testing Coulomb’s Law And Similar Fundamentals Yourself Remains Tricky
• Jenny’s Picks:
  • colibri: CERN VHDL Common Library released for Everyone to Use – Newsletter of the EP department
  • Improved Double-Sided Toner Transfer Method
  • Apple Finally Made AirPods Repairable… Sort Of

Can’t-Miss Articles:

• Roman Telescope Saves Fuel, Doubles Mission
• Lagrange Points And Why You Want To Get Stuck At Them
• Places To Visit: Landschaftspark Duisburg-Nord

Generally making stuff stick to something like a ceiling requires resorting to suction cups, glue or something much more permanent, but [Steve Mould] starts his video featuring a playing card that is clearly defying gravity with no such measures. All that it seems to take is the small vibration motor placed on said playing card, with its vibrations making the card stick like a kind of magic trick.

Although the easy explanation would be that it creates a kind of Bernoulli grip – a common pneumatic, contactless gripping device – [Steve] explains how it’s more complex than that. This vibration adhesion effect doesn’t rely on the same constant pressure drop that a Bernoulli grip experiences within the small gap between the surface and the object. Although a gap is present, it’s much smaller in this case.

Of note is that this effect only occurs when the object is made of a flexible enough material that can vibrate along with the vibration source, in the form of a motor or transducer. As demonstrated in the video, this creates standing waves that affect the surrounding air. When pushed against a rigid surface, these standing waves change into travelling waves, which result in the air that enters this small gap constantly being pushed out and thus lowering the air pressure.

The air pressure between the rigid and flexible surfaces thus becomes lower than that of the surrounding air, creating the resulting suction effect without touching the surface as something like a suction cup would.

One can imagine practical uses for this effect much like with Bernoulli grips. These are especially common in the semiconductor industry for handling delicate items like silicon wafers with zero risk of contamination. In the video it’s shown how you can use the effect to even hold the weight of a person, though they failed to get past a few dozen kilograms with the used setup involving a 400 Watt transducer, possibly due to their ‘ceiling’ not being rigid enough, leading to energy loss.

There are also papers such as this 2025 one by [Siquan Li] et al. who suggest a ‘Micro-Vibration Adhesion’  (VBA) system to help small robots climb up walls for use in repairs and inspection. In their experimental setup they found an adhesion-to-weight ratio exceeding 51 times, making it an interesting way to have small robots defy gravitational pull without a complicated mechanism.

[Michael H Thiesen] had a couple of Elgato Key Lights in his home streaming setup. The only problem was that they would stop responding regularly, requiring a power cycle to get them going again. He never quite pinned down where the problem lay; instead, he set about replacing the light controllers wholesale to provide more reliable functionality.

In place of the original controllers, a pair of ESP32-C3 boards were substituted in. The original design simply had a Realtek controller chip wired into a PCA9635 LED controller, so the swap was as easy as plucking one out and wiring the new microcontroller in its place. The capable ESP32-C3 offers native Matter support, which enabled the new controllers to join [Michael’s] Apple Home setup natively. Running a firmware coded in Rust, the controllers offer power, brightness, and colour-temperature control right in Apple Home. As a bonus, there was no need to use Homebridge to get the lights hooked up to the smarthome setup anymore, eliminating a dependency and a possible source of occasional failures.

Design files are on Github for the curious. We’ve featured other great Elgato hacks before, too, like this nifty capture card firmware hack. If you’re tinkering with your own smarthome hacks, be sure to let us know on the tipsline.

[The Mike Stuff] has an interesting proposition. He asserts that ancient people like the Greeks could have built a form of radio that was purely mechanical. We aren’t sure we agree, but even if it were possible, we are sure it would have sounded awful. You can see the details in the video below.

The idea is that you can compress air with a waterwheel, blow it through a rotating disk with slots in it, and a valve to amplitude modulate the airflow through the disk. Horns like an old gramophone speaker would amplify the signal at both ends. The demodulation is straightforward and doesn’t even require power, like compressed air.

This is a fun idea, but even [Mike] notes it wouldn’t be very good. We suspect you’d just hear a 10 kHz buzz. On the other hand, this would be pretty easy to build if you wanted to test it. Use an electric motor to spin the disk — after all, we’ll stipulate that you could turn a disk with water power, even if speed control is a little challenging.

If you build it, we’d love to hear about it. Just don’t use it to send us an air-radio message. Try e-mail instead. What do you think? Would this work? We get that if it did, it wouldn’t work well, but would it work at all? Let us know what you think.

If you think about it, building regular receivers that are of low performance is easy enough. With a little work, simple receivers can actually work quite well.