RP2040 DMA Hack Makes Another ‘CPU Core’

January 20, 2023 by Dave Rowntree 16 Comments

[Bruce Land] of Cornell University will be a familiar name to many Hackaday readers, searching the site for ‘ECE4760′ will bring up many interesting topics around embedded programming. Every year [Bruce] releases yet more of the students’ work out into the wild to our great delight. This RP2040-based project is a bit more abstract than some previous work and shows yet another implementation of an older hack to utilise the DMA hardware of the RP2040 as another CPU core. While the primary focus of the RP2040 DMA subsystem is moving data between memory spaces, with minimal CPU intervention, the DMA control blocks have some fairly complex behaviour. This allows for a Turing-complete CPU to be implemented purely with the DMA hardware and a sprinkling of memory.

The method ties up three of the twelve DMA channels, and is estimated to have a similar performance to ‘an Arduino’ but [Bruce] doesn’t specify which one of the varied models that could be. But who cares anyway? Programming the CPU is a matter of leveraging the behaviour of the hardware, which is all memory mapped and targetable by the DMA. For example, the CPU can waggle GPIO pins by using the DMA to write values to the peripheral address space. The basic flow can be seen in the image above. DMA0 is used as the program counter, which points DMA1 to an array of DMA control blocks, a sequence of which codes for some of the ‘opcodes’ of the CPU model. DMA0 chains to (hands over control to) DMA1 which reads the control blocks and configures itself accordingly. DMA1 performs whatever data move is programmed, chains to DMA2, which in turn reprograms the DMA0 program counter to point to the next block in the list to be executed by DMA1.

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A wooden table with walnut squares and a maple grid. The table has a large barrel-shaped curve on one end and the other is a representation of a wormhole with what look like two stretched cones connected through a narrow cylinder. The wooden grid looks stretch to follow the curvature of spacetime.

Wormhole Coffee Table Takes Woodworking To Another Dimension

January 20, 2023 by Navarre Bartz 20 Comments

While some people are happy with a simple coffee table to hold their snacks while watching Star Trek reruns, others want their furniture to go where no furniture has gone before. [Olivier Gomis] has definitely satisfied this need with his Wormhole Coffee Table. [YouTube]

The complicated shape and curvature of a (3D representation of a) wormhole isn’t easy to create, but [Gomis] managed to carve one without the aid of a CNC or 3D printer. Starting with walnut planks and maple veneer laminated together, he created a grid stackup to replicate the common representation of spacetime as a 2D grid. Using various arrangements of these grids, he built up the central section of the wormhole which looked like a low poly vase before he put it on the lathe for turning.

The lathe work on this build is simultaneously impressive and terrifying. Turning down the central portion of the wormhole required working between two large spinning squares of walnut, which [Gomis] admits was “scary.” Multiple custom jigs were required to keep parts flat and deal with the extreme curvature of the inside of the wormhole’s opening. If that weren’t enough, if you look down the wormhole, he has installed a set of LED lights that show the spacetime grid continuing on to parts unknown.

If you’d like to see another impressive wormhole, check out this Amazing STARGᐰTE With DHD And Infinity Mirror Wormhole.

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One-Piece Tank Chassis Pushes Print-in-Place To New Heights

January 20, 2023 by Donald Papp 30 Comments

What’s better than 3D printing a tank chassis with working tracks? How about 3D printing the entire thing, moving parts and all, as a single piece? That’s [3D Honza]’s PiPBOT-1, and it’s the culmination of a whole lot of design work.

The design prints flat, then folds up into its final form.

[3D Honza] has been sharing progress pictures and videos on his Twitter account, and just recently released the first version of his design. Version 1.0 is just the mechanics, but he’s already at work on version 2.0 which includes the ability to attach servos to drive the treads. At this writing, the design is currently downloadable directly from his site and includes CAD files, which is great to see.

One part of the design we’d like to draw your attention to is the chunky hinge that doubles as a kind of axial structure making up the body. This allows the tank to print in an unfolded state with the treads and wheels flat on the print bed. After printing, the tank gets folded up a bit like a taco to attain its final form. It’s a clever layout that allows the unit to be printed according to a filament-based 3D printer’s strengths, printing as a single piece that transforms into a small tank chassis, complete with working treads, in a few seconds.

When it comes to vehicles and bots, whether to choose wheels or tracks is a serious question our own Lewin Day has explained thoroughly. And for those of you who choose tracks, this design is great for small devices but don’t forget it’s always possible to go bigger when it comes to 3D-printed tanks.

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Extrusion For The Pottery Shop

January 20, 2023 by Bryan Cockfield 2 Comments

Extrusion is a process for forming materials by forcing them through an opening, which can allow for complex shapes. Aluminum extrusion beams are what most of us are probably thinking of, but plenty of other things are made from extruded material like pipe, heat sinks, and even macaroni. Extrusion can also be used for modelling clay to create uniform sections of rounded clay as a starter material for producing other pottery, and [Justins Makery] has built a custom extruder to do just that.

The build starts with welding together a metal frame to hold the press, and uses a wooden wagon handle to drive the extruder. The handle can be moved up or down the frame to increase the range of motion thanks to a custom bearing and slots cut into the frame’s post. The piston mechanism itself is built out of aluminum plate with a cylinder loosely fitted to it to allow for easy cleaning, and the top of the piston uses a loose-fitting plastic cap cut out of an old cutting board.

With everything in pace, the extruder can make cylinders of clay of any desired thickness thanks to swappable dies. While it doesn’t produce the end result of the workshop directly, it definitely helps to provide the potter with clay of uniform dimensions used for building other pieces of pottery, much like how aluminum extrusions are used to build all kinds of other things as well.

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Machining With Electricity Explored In The Hack Chat

January 20, 2023 by Tom Nardi 16 Comments

As a Hackaday reader, it’s safe to assume you’ve got a better than average understanding of electricity. There’s also an excellent chance you’re familiar with machining, and may even have a lathe or old mill in the workshop. But combining the two, and actually machining a piece of metal with electricity, isn’t something that many home gamers can boast first-hand experience with.

Of course, that doesn’t mean there isn’t an interest. To help answer the burning (or at least, sparking) questions from the community, CEO and founder of Voxel Innovations Daniel Herrington stopped by this week’s Hack Chat to talk about the cutting edge of both electric discharge machining (EDM) and the closely related field of electrochemical machining (ECM). While his company uses the technology to produce components at incredible scales, Daniel got his start tinkering in the garage like so many of us, enabling him to provide both a professional and hobbyist prospective on the technologies.

Naturally, the first big question to be addressed was the difference between EDM and ECM. Put simply, electric discharge machining uses high-voltage to literally blast away material from the workpiece. The resulting finish is generally rough, and progress through the material tends to be slow, but it’s relatively simple to implement.

In contrast electrochemical machining could be thought of as a sort of reverse electroplating process, as the material being removed from the workpiece is dissolved and transferred to the cathode — though in practice the flow of pressurized electrolyte keeps it from actually plating the negatively charged tool. ECM is a faster process than EDM and allows for an exceptionally smooth surface finish, but is considerably more challenging from a technical perspective. Continue reading “Machining With Electricity Explored In The Hack Chat” →

Hackaday Podcast 202: CNC Monks, Acrobot, Bootleg Merch, And The Rise And Fall Of Megahex

January 20, 2023 by Kristina Panos 1 Comment

This week, Editor-in-Chief Elliot Williams and Assignments Editor Kristina Panos stood around and marveled at machinery in its many forms, from a stone-cutting CNC to an acrobatic robot to an AI-controlled Twitch v-tuber. But before all of that, we took a look at the winners of our FPV Vehicle Contest, poured one out for Google Stadia, and Elliot managed to stump Kristina once again with this week’s What’s That Sound. Will you fare better?

Later, we drooled over an open-source smart watch, argued screen printing versus stenciling when it comes to bootleg Hackaday merch, and got into the finer points of punycodes.

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!

And/or download it and listen offline.

Continue reading “Hackaday Podcast 202: CNC Monks, Acrobot, Bootleg Merch, And The Rise And Fall Of Megahex” →

Cassette Player Cupholder Is A Useful But Risky Idea

January 20, 2023 by Lewin Day 36 Comments

The cup was invented in 1570 BC. Despite this, infuriatingly, the cupholder didn’t become common in the automotive world until the early 2000s. Cars built in the years PCH (pre-cupholder) typically also had tape decks. Noticing this relationship, [thephatmaster] designed this useful cassette-deck cupholder accessory.

The design is simple, consisting of a 3D printed ring with a tab that neatly slides into an automotive stereo’s cassette slot. The design does require that the tape deck be empty prior to inserting the cup holder. Given that few cassette players from that era still work, this isn’t much of a drawback. Of course, if you really do need tunes, it wouldn’t be too difficult to integrate a Bluetooth cassette adapter into the printed design.

[thephatmaster] uses the cupholder in a Mercedes W202, and has posted a special inclined version to suit this model. The creator also notes that using it on vehicles like the Mercedes W210 can be a risk. The cupholder typically places the beverage directly above the transmission lever, where any spills can damage switches or other important electronics. Also, the cupholder isn’t designed to work with vertical tape decks, though modification for this layout may be possible.

This build may look silly or pointless to some. But if you’ve ever tried to pull a U-turn in an old manual car while precariously cradling a steaming latte between your legs, you’ll clearly see the value here. It only has to save one pair of pants before it’s paid for itself.

We’ve seen some other creative cupholder hacks before too, like this nifty laptop holder. If you’ve whipped up your own nifty car hacks, send them into the tipsline.