2025 One-Hertz Challenge: ZX Spectrum Is Now A Z80 Frequency Counter

The ZX Spectrum is perhaps most fondly remembered as a home computer and a games machine. [Tito] has grabbed the faithful black plastic box and turned it into a frequency counter as an innovative entry to our 2025 One Hertz Challenge.

The code was prepared in assembly using ZASM—a Z80 online assembler. It works in quite a simple manner. The code runs for one second at a time, counting rising edges on the EAR port of the ZX Spectrum. Those edges are added up to determine the frequency in question, and the job is done. [Tito] has tested the code and found it’s capable of reading frequencies up to 20 KHz. Since it runs on a one second period, it’s thus eligible for entry by meeting the requirements of the One Hertz Challenge. Code is available on Github for the curious.

The ZX Spectrum has a clock speed of 3.5 MHz, meaning it’s not exactly the tool of choice if you’re reading faster signals. We’ve seen similar done before. In any case, this project was a great way to exercise assembly coding skills and to bust out some classic Speccy hardware—and that’s always a good time. If you’ve got your own retrocomputer hacks brewing up in the lab, don’t hesitate to let us know!

Before Macintosh banner with stylized pixelated picture of one

Before Macintosh: The Story Of The Apple Lisa

Film maker [David Greelish] wrote in to let us know about his recent documentary: Before Macintosh: The Apple Lisa.

The documentary covers the life of the Apple Lisa. It starts with the genesis of the Lisa Project at Apple, covering its creation, then its marketing, and finally its cancellation. It then discusses the Apple Lisa after Apple, when it became a collectible. Finally the film examines the legacy of the Apple Lisa, today.

The Apple Lisa was an important step on the journey to graphical user interfaces which was a paradigm that was shifting in the early 1980s, contemporary with the Macintosh and the work at Palo Alto. The mouse. Bitmapped graphics. Friendly error messages. These were the innovations of the day.

Continue reading “Before Macintosh: The Story Of The Apple Lisa”

A photo of a fully assembled PVCSub.

PVCSub: A Submarine From The Plumbing Aisle

Today in the submersibles department our hacker [Rupin Chheda] wrote in to tell us about their submarine project.

This sub is made from a few lengths of PVC piping of various diameters. There is an inflation system comprised of a solenoid and a pump, and a deflation system, also comprised of a solenoid and a pump. The inflation and deflation systems are used to flood or evacuate the ballast which controls depth. There are three pumps for propulsion and steering, one central pump for propulsion and two side pumps for directional control, allowing for steering through differential thrust. Power and control is external and provided via CAT6 cable.

Continue reading “PVCSub: A Submarine From The Plumbing Aisle”

Close-up view of the Solaria Ultra Grand Complication watch

Time, Stars, And Tides, All On Your Wrist

When asked ‘what makes you tick?’ the engineers at Vacheron Constantin sure know what to answer – and fast, too. Less than a year after last year’s horological kettlebell, the 960g Berkley Grand Complication, a new invention had to be worked out. And so, they delivered. Vacheron Constantin’s Solaria Ultra Grand Complication is more than just the world’s most complicated wristwatch. It’s a fine bit of precision engineering, packed with 41 complications, 13 pending patents, and a real-time star tracker the size of a 2-Euro coin.

Yes, there’s a Westminster chime and a tourbillon, but the real novelty is a dual-sapphire sky chart that lets you track constellations using a split-second chronograph. Start the chrono at dusk, aim your arrow at the stars, and it’ll tell you when a chosen star will appear overhead that night.

Built by a single watchmaker over eight years, the 36mm-wide movement houses 1,521 parts and 204 jewels. Despite the mad complexity, the watch stays wearable at just 45mm wide and 15mm thick, smaller than your average Seamaster. This is a wonder of analog computational mechanics. Just before you think of getting it gifted for Christmas, think twice – rumors are it’ll be quite pricey.

2025 One-Hertz Challenge: HP Logic Probe Brought Into The Future

[Robert Morrison] had an ancient HP 545A logic probe, which was great for debugging SMT projects. The only problem was that being 45 years old, it wasn’t quite up to scratch when it came to debugging today’s faster circuitry. Thus, he hacked it to do better, and entered it in our 2025 One Hertz Challenge to boot!

[Robert’s] hack relied on the classic logic probe for its stout build and form factor, which is still useful even on today’s smaller hardware. Where it was lacking was in dealing with circuits running at 100 MHz and above. To rectify this, [Robert] gave the probe a brain transplant with a Sparkfun Alorium FPGA board and a small display. The FPGA is programmed to count pulses while measuring pulse widths and time, and it then drives the display to show this data to the user. There’s also a UART output, and [Robert] is actively developing further logic analyzer features, too.

You might be questioning how this project fits in the One Hertz Challenge, given it’s specifically built for running at quite high speeds. [Robert] snuck it in under the line because it resamples and updates the display on a once-a-second basis. Remember, as per the challenge site—”For this challenge, we want you to design a device where something happens once per second.” We’re giving you a lot of leeway here!

Often, old scopes and probes and other gear are really well built. Sometimes, it’s worth taking the best of the old physical hardware and combining it with modern upgrades to make something stout that’s still useful today. Meanwhile, if you’re cooking up your own neo-retro-logic probes, don’t hesitate to notify the tipsline!

Hackaday Podcast Episode 329: AI Surgery, A Prison Camp Lathe, And A One Hertz Four-Fer

Join Hackaday Editors Elliot Williams and Tom Nardi as they talk about their favorite hacks and stories from the previous week. They’ll start things off with a small Supercon update, and go right into fusion reactors, AI surgeons, planned obsolescence, and robotic cats and dogs. They’ll also go over several entries from the ongoing 2025 One Hertz Challenge, an ambitious flight simulator restoration project, old school lightning detectors, and how Blu-ray won the battle against HD DVD but lost the war against streaming. Stick around to the end to hear an incredible story about a clandestine machine shop in a WWII prisoner of war camp, and the valiant fight to restore communications with the Lunar Trailblazer spacecraft.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Download in DRM-free MP3 and add it to your collection.

Continue reading “Hackaday Podcast Episode 329: AI Surgery, A Prison Camp Lathe, And A One Hertz Four-Fer”

Unlocking The Potential Of A No-Name Handheld Game

The rise of inexpensive yet relatively powerful electronics has enabled a huge array of computing options that would have been unheard of even two decades ago. A handheld gaming PC with hours of battery life, for example, would have been impossible or extremely expensive until recently. But this revolution has also enabled a swath of inexpensive but low-quality knockoff consoles, often running unlicensed games, that might not even reach the low bar of quality set by their sellers. [Jorisclayton] was able to modify one of these to live up to its original promises.

This Ultimate Brick Game, as it is called, originally didn’t even boast the number of games, unlicensed or otherwise, that it claimed to. [Jorisclayton] removed almost all of the internals from this small handheld to help it live up to this original claim. It boasts a Raspberry Pi Zero 2W now as well as a TFT screen and has a number of other improvements including Bluetooth support for external controllers and upgraded audio. A second console was used for donor parts, and some case mods were made as well to accommodate a few extra buttons missing on the original console.

Right now the project is in a prototype phase, as [Jorisclayton] is hoping to use the donor case to build a more refined version of this handheld console in the future. Until then, this first edition upgrade of the original console can run RetroPie, which means it can run most games up through the Nintendo 64 era. RetroPie enables a ton of emulation for old video games including arcade games of the past. This small arcade cabinet uses that software to bring back a bit of nostalgia for the arcade era.