The 6809 Lives On In An FPGA

At one point, the Motorola 6809 seemed like a great CPU. At the time it was a modern 8-bit CPU and was capable of hosting position-independent code and re-entrant code. Sure, it was pricey back in 1981 (about four times the price of a Z80), but it did boast many features. However, the price probably prevented it from being in more computers. There were a handful, including the Radio Shack Color Computer, but for the most part, the cheaper Z80 and the even cheaper 6502 ruled the roost. Thanks to the [turbo9team], however, you can now host one of these CPUs — maybe even a better version — in an FPGA using Verilog.

The CPU may be old-fashioned on the outside, but inside, it is a pipeline architecture with a standard Wishbone bus to incorporate other cores to add peripherals. The GitHub page explains that while the 6809 is technically CISC, it’s so simple that it’s possible to translate to a RISC-like architecture internally. There are also a few enhanced instructions not present on the 6809.

In addition to the source code, you’ll find a thesis and some presentations about the CPU in the repository. While the 6809 might not be the most modern choice, it has the advantage of having plenty of development tools available and is easy enough to learn. Code for the 6800 should run on it, too.

Even using through-hole parts, you can make a 6809 computer fit in a tiny space.You can also break out a breadboard.

Whole-Fruit Chocolate: Skipping The Sugar By Using The Entire Cacao Pod

Images of whole-fruit chocolate formulations after kneading at 31 °C and subsequent heating to 50 °C. The ECP concentration in the sweetening gel and the added gel concentrations into the CM are shown on the x and y axis, respectively. (Credit: Kim Mishra et al., Nature Food, 2024)
Images of whole-fruit chocolate formulations after kneading at 31 °C and subsequent heating to 50 °C. The ECP concentration in the sweetening gel and the added gel concentrations in the CM are shown on the X and Y axes, respectively. (Credit: Kim Mishra et al., Nature Food, 2024)

It’s hard to imagine a world without chocolate, and yet it is undeniable that there are problems associated both with its manufacturing and its consumption. Much of this is due to the addition of sugar, as well as the discarding of a significant part of the cacao pod, which harbors the pulp and seeds. According to a study by [Kim Mishra] and colleagues in Nature Food, it might be possible to ditch the sugar and instead use a mixture of cacao pulp juice (CPJC) and endocarp powder (ECP), which are turned into a sweetening gel.

This gel replaces the combination of sugar with an emulsifier (lecithin or something similar) in current chocolate while effectively using all of the cacao pod except for the husk. A lab ran a small-scale production, with two different types of whole-fruit chocolate produced, each with a different level of sweetness, and given to volunteers for sampling. Samples had various ECP ratios in the gel and gel ratios in the chocolate mixture with the cacao mass (CM).

With too much of either, the chocolate becomes crumbly, while with too little, no solid chocolate forms. Eventually, they identified a happy set of ratios, leading to the taste test, which got an overall good score in terms of chocolate taste and sweetness. In addition to being able to skip the refined sugar addition, this manufacturing method also cuts out a whole supply chain while adding significantly more fiber to chocolate. One gotcha here is that this study focused on dark chocolate, but then some chocolate fans would argue vehemently that anything below 50% cacao doesn’t qualify as chocolate anymore, while others scoff at anything below 75%.

Matters of taste aside, this study shows a promising way to make our regular chocolate treat that much healthier and potentially greener. Of course, we want to know how it will print. Barring that, maybe how it engraves.

Digital Meter From 1973, A Teardown

[Thomas] found an interesting probable millivoltmeter with some Beckman displays. Like many instruments from that time period, this one had a lot of tobacco smoke residue inside. The display unit inside had a sticker that not only showed the company that made it, but also had their Telex number on it, another sign of the times. You can see the device in the video below.

The unit looked like a one-off made by a hobbyist or a technician but the case looked suspiciously like old Bang and Olfusen equipment. Someone in the video comments mentions it was built for the service department.

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Play Giant Tetris On Second-Floor Window

Sometimes it seems like ideas for projects spring out of nothingness from a serendipitous set of circumstances. [Maarten] found himself in just such a situation, with a combination of his existing Tetris novelty lamp and an awkwardly-sized window on a second-floor apartment, he was gifted with the perfect platform for a giant playable Tetris game built into that window.

To make the giant Tetris game easily playable by people walking by on the street, [Maarten] is building as much of this as possible in the browser. Starting with the controller, he designed a NES-inspired controller in JavaScript that can be used on anything with a touch screen. A simulator display was also built in the browser so he could verify that everything worked without needing the giant display at first. From there it was on to building the actual window-sized Tetris display which is constructed from addressable LEDs arranged in an array that matches the size of the original game.

There were some issues to iron out, as would be expected for a project with this much complexity, but the main thorn in [Maarten]’s side was getting his controller to work in Safari on iPhones. That seems to be mostly settled and there were some other gameplay issues to solve, but the unit is now working in his window and ready to be played by any passers-by, accessed by a conveniently-located QR code. Tetris has been around long enough that there are plenty of unique takes on the game, like this project from 2011 that uses Dance Dance Revolution pads for controllers.

A person holds a glass jar in their left hand and a spark plug in their right atop a white cylindrical canister. The jar and canister are sitting on top of a green cutting mat.

Spark Plug Becomes Glass Cutter

Sometimes a hack doesn’t need to be rocket science to be useful. Take for instance [MofigoDIY] using an old spark plug to build a glass cutter.

Sure, going to grab a glass cutter at the hardware store might be easy, but there’s something satisfying about going the DIY route. [MofigoDIY]’s version of this classic hack is a bit more refined than the quick and dirty route of smashing the spark plug alumina and hot gluing it into a tube.

After using a rotary tool to cut off the threads and expose the narrow part of the ceramic, [MofigoDIY] grinds it down to a fine point. This lets the spark plug itself become the handle, so you don’t need any additional parts to make the cutter. Toward the end of the video, a heated wire is used to break a glass jar apart after it was scored which might be of interest even if you already have a glass cutter. Once you’re finished making your glass cutter, make sure you dispose of any chips left over, since ceramic spark plug fragments are considered burglary tools in some areas.

Would you rather just build the glass up additively? How about using a laser cutter to sinter glass or 3D printing fused silica using a polymerized composite precursor?

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Illustrated Kristina with an IBM Model M keyboard floating between her hands.

Keebin’ With Kristina: The One With The Auto Harp Typewriter

An extremely large split keyboard with giant knobs, and pedals underneath the desk.
Image by [crazymittens-r] via reddit
Where do I even begin with this one? Let’s start with the reasoning behind this giant beast’s existence, and that is medical necessity. [crazymittens-r] needed something that would let them keep working, and after many hours and many versions, this is the current iteration of their ArcBoard, which looks like it could control a spaceship.

You can read all about this version on GitHub, but here’s the gist — you’re looking at a split keyboard with dual macro pads, rotary encoders, and a built-in trackball. And oh yeah, there are pedals, too. Those are a whole other thing.

In this revision, [crazymittens-4] said no to hand-wiring and instead went with custom flexible PCBs. The encoders now have push-button LED screens, and overall, there are “more LEDs than QMK can handle”. There’s even a secret keyboard within the keyboard! I can’t express how much I want to put my hands on this thing.

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Rotary Phone Lives On As Arduino Kitchen Timer

It’s safe to say that few people still use rotary phones on a daily basis. Hell, most of us don’t even use landline telephones anymore. But just because these classic phones are no longer being used for their original purpose doesn’t necessarily mean they’re doomed to become e-waste.

[Scott-28] recently sent in a particularly well-documented project that turned an antique rotary phone into a digital kitchen timer using an internal Arduino. While we’re not sure practical is a word most folks would use to describe the resulting device, it’s certainly a conversation starter, and the details on how it was all implemented make for an interesting read.

As explained in the README, [Scott-28] first used an oscilloscope to figure out the pulses generated by the phone’s dial. From there, it was relatively easy to connect the dial to one of the pins on an Arduino Uno to determine which numbers the user had entered. The trickier part was getting the original bells to work — in North America, it takes up to 90 VAC to get a phone’s ringer going, which is quite a bit more than the lowly Arduino can handle.

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