Coroutines In C

July 14, 2025 by 20 Comments

It is virtually a rite of passage for C programmers to realize that they can write their own cooperative multitasking system. C is low-level enough, and there are several ways to approach the problem, so, like Jedi light sabers, each one is a little bit different. [Christoph Wolcher] took his turn, and not only is his system an elegant hack, if that’s not an oxymoron, it is also extremely well documented.

Before you dig in, be warned. [Christoph] fully admits that you should use an RTOS. Or Rust. Besides, after he finished, he discovered the protothreads library, which does a similar task in a different way that is both more cool and more terrible all at the same time.

Once you dig in, though, you’ll see the system relies on state machines. Just to prove the point, he writes a basic implementation, which is fine, but hard to parse and modify. Then he shows a simple implementation using FreeRTOS, which is fine except for, you know, needing FreeRTOS.

Using a simple set of macros, it is possible to get something very similar to the RTOS version that runs independently, like the original version. Most of the long code snippets show you what code the macros generate. The real code is short and to the point.

Multiprocessing is a big topic. You can have processes, threads, fibers, and coroutines. Each has its pros and cons, and each has its place in your toolbox.

Hacking When It Counts: DIY Prosthetics And The Prison Camp Lathe

July 14, 2025 by 12 Comments

There are a lot of benefits to writing for Hackaday, but hands down one of the best is getting paid to fall down fascinating rabbit holes. These often — but not always — delightful journeys generally start with chance comments by readers, conversations with fellow writers, or just the random largesse of The Algorithm. Once steered in the right direction, a few mouse clicks are all it takes for the properly prepared mind to lose a few hours chasing down an interesting tale.

I’d like to say that’s exactly how this article came to be, but to be honest, I have no idea where I first heard about the prison camp lathe. I only know that I had a link to a PDF of an article written in 1949, and that was enough to get me going. It was probably a thread I shouldn’t have tugged on, but I’m glad I did because it unraveled into a story not only of mechanical engineering chops winning the day under difficult circumstances, but also of how ingenuity and determination can come together to make the unbearable a little less trying, and how social engineering is an important a skill if you want to survive the unsurvivable.

Continue reading “Hacking When It Counts: DIY Prosthetics And The Prison Camp Lathe” →

Two views of a motor are shown. On the left, a ring of copper-wire-wound stator arms is visible inside a ring of magnets. Inside this, a planetary gearbox is visible, with three mid-sized gears surrounding a small central gear. On the right, the same motor is shown, but with the internal components mostly covered by a black faceplate with brass inserts.

A Budget Quasi-Direct-Drive Motor Inspired By MIT’s Mini Cheetah

July 14, 2025 by 27 Comments

It’s an unfortunate fact that when a scientist at MIT describes an exciting new piece of hardware as “low-cost,” it might not mean the same thing as if a hobbyist had said it. [Caden Kraft] encountered this disparity when he was building a SCARA arm and needed good actuators. An actuator like those on MIT’s Mini Cheetah would have been ideal, but they cost about $300. Instead, [Caden] designed his own actuator, much cheaper but still with excellent performance.

The actuator [Caden] built is a quasi-direct-drive actuator, which combines a brushless DC motor with an integrated gearbox in a small, efficient package. [Caden] wanted all of the custom parts in the motor to be 3D printed, so a backing iron for the permanent magnets was out of the question. Instead, he arranged the magnets to form a Halbach array; according to his simulations, this gave almost identical performance to a motor with a backing iron. As a side benefit, this reduced the inertia of the rotor and let it reverse more easily.

To increase torque, [Caden] used a planetary gearbox with cycloidal gear profiles, which may be the stars of the show here. These reduced backlash, decreased stress concentration on the teeth, and were easier to 3D print. He found a Python program to generate planetary gearbox designs, but ended up creating a fork with the ability to export 3D files. The motor’s stator was commercially-bought and hand-wound, and the finished drive integrates a cheap embedded motor controller. Continue reading “A Budget Quasi-Direct-Drive Motor Inspired By MIT’s Mini Cheetah” →

Explore The Granddaddy Of All Macs With LisaGUI

July 14, 2025 by 23 Comments

Sure, Apple’s Lisa wasn’t the first computer released with a graphical user interface — Xerox was years ahead with the Alto and the Star workstation — but Lisa was the first that came within the reach of mere mortals. Which doesn’t mean many mortals got their hands on one; with only about 10,000 sold, they were never common, and are vanishingly rare nowadays. Enter [Andrew Yaros], who has graced the world with LisaGUI, an in-browser recreation of the Lisa Office System in Javascript.

Lisa’s GUI varies from modern conventions in a few interesting ways. For one, it is much more document-focused: if you double-click on LisaType, you do not start the program. Instead you “tear off” a document from the “pad” icon of LisaType, which you can then open with another double click. The desktop is also not a folder for files to live permanently, but a temporary space. You can “set aside” a file to the desktop, but its home on disk is unchanged.

Unlike the family of Mac emulators, LisaGUI does not purport to be a perfect replica. [Andrew] has made a few quality-of-life improvements for modern users, as well as a few innovations of his own. For instance, menus are now “sticky”– on the Lisa, you had to hold down the mouse to keep them open, and release on the appropriate entry. LisaGUI leaves the menu open for you to click the entry, as on a later Macintosh.

Obviously the menu bar clock and FPS counter are not native to the Lisa; nor is the ability to theme the icons and change (1-bit) colour palettes. The ability to draw unique icons to assign to documents is all [Andrew], but is something we wish we had back in the day. He also makes no attempt to enforce the original aspect ratio, so you’ll be dragging the window to get 4:3 if that’s your jam.

Right now it does not look as though there’s much original software aside from LisaType. We would have loved to see the famous LisaProject, which was the original “killer app” that led NASA to purchase the computer. Still, this is an Alpha and it’s possible more software is to come, if it doesn’t run afoul of Apple’s IP. Certainly we are not looking too hard at this gift horse’s chompers. What’s there is plenty to get a feel for the system, and LisaGUI should be a treat for retrocomputer enthusiasts who aren’t too anal about period-perfect accuracy.

We stumbled across this one in a video from [Action Retro] in which he (the lucky dog) also shows off his Lisa II, the slightly-more-common successor.

Citizen Science Is All Fun And Games

July 13, 2025 by 7 Comments

You are probably familiar with initiatives like Seti@Home, where you donate unused computer power to some science project that needs computer cycles. [Jeff Yoshimi] wants to borrow your most powerful computer: your brain. The reason: cancer research.

[Jeff’s] recent book, Gaming Cancer, has three examples: Eterna, Foldit, and Nanocrafter. All three make games out of creating biological molecules. With Foldit, you create proteins in a bonsai-like fashion. EteRNA is more like Sudoku for RNA. Nanocrafter used DNA strands as puzzle pieces, although it is no longer operational. Their website, amusingly, looks like it was taken over by a slot machine site and a probably AI-generated text tries to convince you that slot machines are much like fusing DNA strands.

What can these projects do? Eterna’s open vaccine challenge used gameplay to help design RNA molecules for vaccines that don’t require ultra-cold storage, and the results drove improvements in real-life vaccines.

There have been several science fiction stories that center on the idea that a game of some sort might be an entrance test to a super-secret organization (The Last Starfighter or Stargate: Universe, for example). Maybe a future science game will trigger scholarship or job offers. It could happen.

We like citizen science. Zooniverse does a good job of making it fun, but maybe not to the level of a game. You can make contributions in space, or even right here on Earth.

Lit up coffee table

Smart Coffee Table To Guide Your Commute

July 13, 2025 by 8 Comments

One of the simple pleasures of life is enjoying a drive to work… only to get stuck in traffic that you could’ve known about if you just checked before your daily commute. Who are we kidding? There’s almost nothing worse. [Michael Rechtin] saw this as a great opportunity to spruce up his living room with something practical, a coffee table that serves as a traffic map of Cincinnati.

The table itself is fairly standard with mitered joints at the corners and coated in polyurethane. Bolt on a few legs, and you’ve got a coffee table. But the fun comes with the fancy design on top. A CNC-cut map of Cincinnati is laid out under a sheet of glass. Roads and rivers are painted for a nice touch.

Of course, none of the woodcraft is what gets the attention. This is where the LED light show comes in. On top of the map resides an animated display of either road conditions or the other five pre-programmed animations. The animations include color-coded highways or the good ole’ gamer RGB. To control all of the topographic goodness, a Raspberry Pi is included with some power regulation underneath the table. Every minute, the Pi is able to grab live traffic data from the cloud to display on top.

A looker, this project shows how our hacking fun can be integrated directly into our everyday life in more subtle ways. When we want to decorate ourselves, however, we might want to turn to more personal fare. Check out this miniature liquid simulation pendant for some more everyday design.

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Hackaday Links: July 13, 2025

July 13, 2025 by 8 Comments

There’s interesting news out of Wyoming, where a coal mine was opened this week. But the fact that it’s the first new coal mine in 50 years isn’t the big news — it’s the mine’s abundance of rare earth elements that’s grabbing the headlines. As we’ve pointed out before, rare earth elements aren’t actually all that rare, they’re just widely distributed through the Earth’s crust, making them difficult to recover. But there are places where the concentration of rare earth metals like neodymium, dysprosium, scandium, and terbium is slightly higher than normal, making recovery a little less of a challenge. The Brook Mine outside of Sheridan, Wyoming is one such place, at least according to a Preliminary Economic Assessment performed by Ramaco Resources, the mining company that’s developing the deposit.

The PEA states that up to 1,200 tons of rare earth oxides will be produced a year, mainly from the “carbonaceous claystones and shales located above and below the coal seams.” That sounds like good news to us for a couple of reasons. First, clays and shales are relatively soft rocks, making it less energy- and time-intensive to recover massive amounts of raw material than it would be for harder rock types. But the fact that the rare earth elements aren’t locked inside the coal is what’s really exciting. If the REEs were in the coal itself, that would present something similar to the “gasoline problem” we’ve discussed before. Crude oil is a mixture of different hydrocarbons, so if you need one fraction, like diesel, but not another, like gasoline, perhaps because you’ve switched to electric vehicles, tough luck — the refining process still produces as much gasoline as the crude contains. In this case, it seems like the coal trapped between the REE-bearing layers is the primary economic driver for the mine, but if in the future the coal isn’t needed, the REEs could perhaps be harvested and the coal simply left behind to be buried in the ground whence it came.

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