Who Had “New OS For The Z80” On Their 2026 Bingo Card?

April 12, 2026 by Tyler August 2 Comments

Some might say the venerable Z80 doesn’t need another operating system, but [Scott Baker] obviously disagrees. He has come up with a brand new, from scratch OS called NostOS for the Z80-based RC2014 homebrew retrocomputer. [Scott] describes it as CP/M-like, but it’s not CP/M– in fact, it’s totally incompatible with CP/M–and has a few tricks of its own up its sleeve.

As you might expect of an operating system for this vintage of hardware, it is “rommable” — that is, designed to run from read-only-memory, and fit inside 64kB. It of course supports banking memory to go higher than that 16 bit limit, and natively supports common serial devices, along with the good old WD37C65 floppy controller to get some spinning rust into the game. Of course if you don’t have floppies you can plug in a compact flash card– try that with CP/M– or, interestingly Intel Bubble Memory. [Scott] has a soft-spot for bubble memory, which at one point seemed poised to replace both hard drives and RAM at the same time. We also appreciate that he included drivers for vacuum fluorescent displays, another forgotten but very cool technology. Back in the day, this operating system would have enabled a very cool little computer, especially when you take his implementation of text-to-speech with the SP0256A-AL2 chip. Fancy a game of talking Zork? Yes, he ported Zork, and yes, it talks.

The whole thing is, of course, open-source, and available on [Scott]’s GitHub. Unlike too many open-source projects, the documentation is top-notch, to the point that we could picture getting it in a three-ring binder with a 5 1/4 floppy on the inside cover. If you like video, we’ve embedded [Scott]’s walkthrough but his blog and the docs on GitHub have everything there and more if you’re not into rapidly-flickering-pixels as an information exchange medium.

[Scott] isn’t wedded to Zilog, for the record; this OS should run on an Intel 8080, perhaps like the one in the Prompt 80 he restored last year.

Thanks to [Scott Baker] for the tip!

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Vacuum Fluorescent Displays Explained

January 23, 2026 by Maya Posch 11 Comments

After having been sent a vacuum fluorescent display (VFD) based clock for a review, [Anthony Francis-Jones] took the opportunity to explain how these types of displays work.

Although VFDs are generally praised for their very pleasant appearance, they’re also relatively low-power compared to the similar cathode ray tubes. The tungsten wire cathode with its oxide coating produces the electrons whenever the relatively low supply voltage is applied, with a positively charged grid between it and the phosphors on the anode side inducing the accelerating force.

Although a few different digit control configurations exist, all VFDs follow this basic layout. The reason why they’re also called ‘cold cathode’ displays is because the cathode doesn’t heat up nearly as hot as those of a typical vacuum tube, at a mere 650 °C. Since this temperature is confined to the very fine cathode mesh, this is not noticeable outside of the glass envelope.

While LCDs and OLED displays have basically eradicated the VFD market, these phosphor-based displays still readily beat out LCDs when it comes to viewing angles, lack of polarization filter, brightness and low temperature performance, as LC displays become extremely sluggish in cold weather. Perhaps their biggest flaw is the need for a vacuum to work, inside very much breakable glass, as this is usually how VFDs die.

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The clock and the rebuilt calculator from which its VFD was donated.

An RPN Calculator And A Bonus VFD Clock From Casio Revival

January 5, 2026 by Tyler August 15 Comments

Have you heard the saying “the problem is the solution”? It seems to originate in the permaculture movement, but it can apply equally well to electronics. Take the problem [shiura] had: a Casio Mini CM-602 that had let out the magic smoke. The solution was a twofer: rebuild the Casio into a modern number cruncher with Reverse Polish Notation (RPN), and save the Vacuum Fluorescent Display (VFD) for a gorgeous WiFi clock.

[shiura]’s write-up includes a helpful guide for reverse engineering the pins on this sort of VFD, if you don’t happen to have the same model calculator (or VFD tube) they’re working with. If you’ve done this sort of thing, you know what to expect: power it up and kill power to the pins, one by one, to map out which segments or characters go out, thereby identifying the anodes and grid electrodes. The cathodes had already been ID’d from looking at the PCB. After that it’s just a matter of wiring the VFD to an ESP32 via a transistor array to get the voltages right, and voila! Clock. The code and case design files for this clock — including an editable .blend — are available via GitHub.

The calculator half of the project is an incredibly elegant hack that relies on the fact that the Casio’s CPU has the same pin pitch as modern micros: 2.54 mm, or 0.1″, so an RP2040 zero can sit in the footprint of the original CPU, scanning the keypads with its GPIO. Then an I2C display is separately wired up to replace the clockified VFD. Perhaps some driver circuitry for the VFD died, or [shiura] salvaged the display before deciding to save the calculator, because otherwise we see no reason why this brain transplant couldn’t be done while keeping the original display. Admittedly having two lines on the display instead of one make the “new” calculator a tad more usable. The code for that is also available on GitHub, and while the readme is in Japanese, machine translations have gotten pretty good and the code is quite readable on its own.

Longtime readers will likely be familiar with [shiura]’s work, with a number of finely crafted clocks having been featured from the Japanese maker, along with vintage pocket computer repairs. Bringing both together makes this twin hack particularly on-brand.

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ESP32 Invades Old TV Box: Forecast More Than Just Channels

October 22, 2025 by Matt Varian 5 Comments

Obsolete hardware is all around us, and some of it has some pretty interesting tech buried within. One such device is an old Belgacom TV Box. Instead of using the ubiquitous LCD screen, it uses a VFD display for its user interface, and [Jean] has taken control of it with the ESPTimeCastVFD project.

Inside this box is a mix of two different 7-segment displays, which he uses to show the time and date, and 12 VFD displays, which are used to show weather data. To get the display working, the box was taken apart, and there were a few different areas [Jean] had to tap into: power for the soon-to-be-embedded ESP32-WROOM-32, as well as tying into the SPI lines to control the VFD. [Jean] also needed a 3.3V to 5V level shifter, and for this he used a 74LS125N dating all the way back to 1978.

The ESPTimeCast project, which we’ve featured here before, handles a lot of the time display and weather forecast shown on the front panel. However, [Jean] did have to add support for the VFD display, as well as adding wind speed to the display—as one of his uses for this is to judge the day’s suitability for flying RC planes. Once powered up, the ESP32 hosts a WiFi access point, allowing you to connect to it and set the configuration of the device, such as location, WiFi credentials, what displays you want to see, and many more. Thank you [Jean] for sending in your hack, saving this device from a landfill by turning it into a personalized display! Be sure to check out some of our other weather displays we’ve featured!

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Soviet Calculator Teardown Reveals Similarities And Differences

June 6, 2025 by Zoe Skyforest 12 Comments

Tearing down hardware from different parts of the world can be revealing, showing unique parts, techniques, and tricks employed by engineers living in a very different world from our own. To that end, [msylvain59] has been kind enough to give us a look inside the Elektronika MK-26—a calculator built in the former Soviet Union.

There’s lots of interesting stuff to see from the get-go. The oddball button pad is covered in Cyrillic symbols, quite alien to those of us more accustomed to the Latin character set. It’s also constructed somewhat unlike more familiar models from Western-aligned companies like Casio or Commodore. It also rattles when shaken, which doesn’t inspire confidence. Inside, it’s got old-school brown PCBs without the usual green solder mask, a chunky IC in a weird package, and display is via a power-hungry VFD.

It doesn’t look so totally alien inside; much of the construction is pretty typical of the mid-1970s, wherever you went around the world. The most striking differences are more in the graphics and visual design than anything else.

Ultimately, there are reasons why manufacturers around the world tend to converge on similar techniques. Generally, it’s because it’s more economical or easier to do things a certain way. And yet, we still see regional variances because conditions, technologies, and parts availability varies around the world. This teardown highlights that quite clearly.

If you’re just getting a taste for Soviet hardware teardowns, you’ll love this video diving inside a real Soyuz clock.

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Inside Vacuum Fluorescent Displays

January 29, 2025 by Al Williams 2 Comments

VFDs — vacuum fluorescent displays — have a distinctive look, and [Anthony Francis-Jones] is generally fascinated with retro displays. So, it makes sense that he’d build a VFD project as an excuse to explain how they work. You can see the video below.

VFDs are almost miniature CRTs. They are very flexible in what they display and can even use color in a limited way. The project [Anthony] uses as an example is an indicator to show the video number he’s currently making.

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VFD Tube Calculator Shows Off Wide Array Of Skills

June 4, 2024 by Tom Nardi 3 Comments

With all the tools and services available to us these days, it’s hard to narrow down a set of skills that the modern hacker or maker should have. Sure, soldering is a pretty safe bet, and most projects now require at least a little bit of code. But the ability to design 3D printable parts has also become increasingly important, and you could argue that knowledge of PCB design and production is getting up there as well. With home laser cutters on the rise, a little 2D CAD wouldn’t hurt either. So on, and so on.

If you ever wanted an example of the multitude of skills that can go into a modern hardware project, take a look at this gorgeous Vacuum Fluorescent Display (VFD) tube calculator built by [oskar2517]. As fantastic as the final product is, we were particularly impressed with everything it took to get this one over the finish line.

A .7 mm walnut veneer covers the pieced together plywood frame.

It’s got it all: 3D printed parts, a laser cut wooden frame, a custom PCB, and even a bit of old school woodworking. To top it all off, the whole thing has been meticulously documented.

But what’s perhaps most impressive here is that [oskar2517] was approaching most of these techniques for the first time. They had never before worked with IV-12 tubes, designed an enclosure in 3D, had parts laser cut, applied wood veneer, or designed a custom PCB. They did have solid experience writing code in C at least, which did make developing the Arduino firmware a bit easier.

Although they might look outwardly similar, VFD tubes like the IV-12 are easier to work with than Nixie tubes thanks to their lower operating voltage. That said, a look through our archives shows that projects using Nixies outnumber VFD tubes by nearly four to one, so there’s no shortage of folks willing to take on the extra effort for that sweet warm glow.