Hackaday Links: February 18, 2024

February 18, 2024 by Dan Maloney 17 Comments

So it turns out that walking around with $4,000 worth of hardware on your head isn’t quite the peak technology experience that some people thought it would be. We’re talking about the recently released Apple Vision Pro headset, which early adopters are lining up in droves to return. Complaints run the gamut from totally foreseeable episodes of motion sickness to neck pain from supporting the heavy headset. Any eyeglass wearer can certainly attest to even lightweight frames and lenses becoming a burden by the end of the day. We can’t imagine what it would be like to wear a headset like that all day. Ergonomic woes aside, some people are feeling buyer’s remorse thanks to a lack of apps that do anything to justify the hefty price tag. The evidence for a wave of returns is mostly gleaned from social media posts, so it has to be taken with a grain of salt. We wouldn’t expect Apple to be too forthcoming with official return figures, though, so the ultimate proof of uptake will probably be how often you spot one in the wild. Apart from a few cities and only for the next few weeks, we suspect sightings will be few and far between.

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Designing A Macintosh-to-VGA Adapter With An LM1881

October 7, 2023 by Maya Posch 3 Comments

Old-school Macintosh-to-VGA adapter. Just solve for X, set the right DIP switches and you’re golden.

If you’re the happy owner of a vintage Apple system like a 1989 Macintosh IIci you may know the pain of keeping working monitors around. Unless it’s a genuine Apple-approved CRT with the proprietary DA-15-based video connector, you are going to need at least an adapter studded with DIP switches to connect it to other monitors. Yet as [Steve] recently found out, the Macintosh’s rather selective use of video synchronization signals causes quite a headache when you try to hook up a range of VGA-equipped LCD monitors. A possible solution? Extracting the sync signal using a Texas Instruments LM1881 video sync separator chip.

Much of this trouble comes from the way that these old Apple systems output the analog video signal, which goes far beyond the physical differences of the DA-15 versus the standard DE-15 D-subminiature connectors. Whereas the VGA standard defines the RGB signals along with a VSYNC and HSYNC signal, the Apple version can generate HSYNC, VSYC, but also CSYNC (composite sync). Which sync signal is generated depends on what value the system reads on the three sense pins on the DA-15 connector, as a kind of crude monitor ID.

Theoretically this should be easy to adapt to, you might think, but the curveball Apple throws here is that for the monitor ID that outputs both VSYNC and HSYNC you are limited to a fixed resolution of 640 x 870, which is not the desired 640 x 480. The obvious solution is then to target the one monitor configuration with this output resolution, and extract the CSYNC (and sync-on-green) signal which it outputs, so that it can be fudged into a more VGA-like sync signal. Incidentally, it seems that [Steve]’s older Dell 2001FP LCD monitor does support sync-on-green and CSYNC, whereas newer LCD monitors no longer list this as a feature, which is why now more than a passive adapter is needed.

Although still a work-in-progress, so far [Steve] has managed to get an image on a number of these newer LCDs by using the LM1881 to extract CSYNC and obtain a VSYNC signal this way, while using the CSYNC as a sloppy HSYNC alternative. Other ICs also can generate an HSYNC signal from CSYNC, but those cost a bit more than the ~USD$3 LM1881.

$13 Scope And Logic Analyzer Hits 18 Msps

September 26, 2023 by Al Williams 31 Comments

We aren’t sure what’s coolest about [Richard Testardi’s] Flea-Scope. It costs about $13 plus the cost of making the PCB. It operates at 18 million samples per second. It also doesn’t need any software — you connect to it with your browser! It works as an oscilloscope, a logic analyzer, and a waveform generator. Not bad. The board is basically a little life support around a PIC32MK and the software required to run it.

Of course, for $13, you need to temper your expectations. One analog input reads from -6 to 6V (hint: use a 10X probe). The goal was for the instrument to be accurate within 2%. There are also nine digital inputs sampled simultaneously with the analog sampling. The signal generator portion can output a 4 MHz square wave or a 40 kHz arbitrary waveform.

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Reverse-engineering The Milwaukee M18 Redlink Protocol

September 15, 2023 by Maya Posch 19 Comments

In an ideal world, every single battery pack for power tools would use the same physical interface and speak a clearly documented protocol with chargers. Since we live in a decidedly less-than-ideal world, we get to enjoy the fun pastime of reverse-engineering the interfaces and protocols of said battery packs.

A recent video from the [Tool Scientist] goes over what is already known about the Milwaukee M18 Redlink protocol, used with the manufacturer’s M18-series of batteries, before diving into some prodding and poking of these packs’ sensitive parts to see what comes out of their interface.

Previously, [Buy It Fix It] shared their findings on Reddit, covering the basic protocol, including the checksum method, but without an in-depth analysis of the entire charging protocol. Meanwhile [Quagmire Repair] performed an in-depth teardown and reverse-engineering of the M18 hardware, including the circuitry of the BMS.

Putting these two things together, [Tool Scientist] was able to quickly get some of his M18 packs strapped down into the analysis chair for both passive analysis, as well as the effect of overvoltage, undervoltage, overheating and freezing the battery pack on the output reported by the battery’s BMS.

One of the lists of commands and response messages obtained by [Tool Scientist] on YouTube.

The result is a rather comprehensive list of instructions obtained under these various conditions, including a fault condition (05) returned by the BMS of one pack indicating its likely demise. Overall, it does not appear to be a particularly special (or well-designed) protocol, but it does make for a good reverse-engineering target, while adding to the body of collective knowledge on these widely available battery packs.

Hopefully the same inertia that prevents people from moving outside the designated power tool ecosystem due to the incompatible battery packs will also ensure that this level of knowledge will remain relevant for the foreseeable future, especially since the manufacturers of knock-off battery packs seem rather unwilling to share the results of their own reverse-engineering efforts.

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Old Style 1802 Computer Has MMU

July 21, 2023 by Al Williams 8 Comments

When you think of an MMU — a memory management unit — you probably think of a modern 32-bit computer. But [Jeff Truck] has a surprise. His new RCA 1802 computer has bank switching, allowing the plucky little processor to address 256K of RAM. This isn’t just the usual bank-switching design, either.

The machine has several unique features. For example, an Arduino onboard can control the CPU so that you can remotely control the bus. It does not, apparently, stand in for any of the microprocessor support chips. It also doesn’t add additional memory or control its access.

The 256K of memory is under the control of the MMU board. This board generates two extra address bits by snooping the executing instruction and figures out what register is involved in any memory access. Memory in the MMU stores a table that lets you set different memory pages for each register. This works even if the register is not explicit and also for the machine’s DMA and instruction fetch cycles. If you know about the RCA “standard call and return technique,” which also needed a little patching for the MMU. [Jeff] covers that at the end of the video below.

This is a very simple version of a modern MMU and is an impressive trick for a 50-something-year-old CPU. We were surprised to hear — no offense to [Jeff] — that the design worked the first time. Impressive! There’s also some 3D printing and other tips to pick up along the way. But we were super impressed with the MMU. You might never have to do this yourself (although you could), but you can still marvel that it can be done at all.

We have a soft spot for the 1802s, real or emulated. The original ELF was great, but 256K is a lot better than the original 256 bytes!

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Lighting Up With Chemistry, 1823-Style

July 19, 2023 by Dan Maloney 9 Comments

With our mass-produced butane lighters and matches made in the billions, fire is never more than a flick of the finger away these days. But starting a fire 200 years ago? That’s a different story.

One method we’d never heard of was Döbereiner’s lamp, an 1823 invention by German chemist Johann Wolfgang Döbereiner. At first glance, the device seems a little sketchy, what with a tank of sulfuric acid and a piece of zinc to create a stream of hydrogen gas ignited by a platinum catalyst. But as [Marb’s Lab] shows with the recreation in the video below, while it’s not exactly as pocket-friendly as a Zippo, the device actually has some inherent safety features.

[Marb]’s version is built mainly from laboratory glassware, with a beaker of dilute sulfuric acid — “Add acid to water, like you ought-er!” — bathing a chunk of zinc on a fixed support. An inverted glass funnel acts as a gas collector, which feeds the hydrogen gas to a nozzle through a pinch valve. The hydrogen gas never mixes with oxygen — that would be bad — and the production of gas stops once the gas displaces the sulfuric acid below the level of the zinc pellet. It’s a clever self-limiting feature that probably contributed to the commercial success of the invention back in the day.

To produce a flame, Döbereiner originally used a platinum sponge, which catalyzed the reaction between hydrogen and oxygen in the air; the heat produced by the reaction was enough to ignite the mixture and produce an open flame. [Marb] couldn’t come up with enough of the precious metal, so instead harvested the catalyst from a lighter fluid-fueled hand warmer. The catalyst wasn’t quite enough to generate an open flame, but it glowed pretty brightly, and would be more than enough to start a fire.

Hats off to [Marb] for the great lesson is chemical ingenuity and history. We’ve seen similar old-school catalytic lighters before, too.

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Hackaday Links: June 18, 2023

June 18, 2023 by Dan Maloney 19 Comments

Will it or won’t it? That’s the question much on the minds of astronomers, astrophysicists, and the astro-adjacent this week as Betelgeuse continued its pattern of mysterious behavior that might portend a supernova sometime soon. You’ll recall that the red giant star in the constellation Orion went through a “great dimming” event back in 2019, where its brightness dipped to 60% of its normal intensity. That was taken as a sign that perhaps the star was getting ready to explode — or rather, that the light from whatever happened to the star 548 years ago finally reached us — and was much anticipated by skywatchers, yours truly included. As it turned out, the dimming was likely caused by Betelgeuse belching forth an immense plume of dust, temporarily obscuring our view of its light. Disappointing.

Those who gave up on the hope of seeing a supernova might have done so too fast, though, because now, the star seems to be swinging the other way and brightening. It briefly became the brightest star in Orion, nearly outshining nearby Sirius, the brightest star in the sky. So what does all this on-again, off-again business mean? According to Dr. Becky, a new study — not yet peer-reviewed, so proceed with caution — suggests that the star could go supernova in the next few decades. The evidence for this is completely unrelated to the great dimming event, but by analyzing the star’s long history of variable brightness. The data suggest that Betelgeuse has entered the carbon fusion phase of its life, a period that only lasts on the scale of a hundred years for a star that size. So we could be in for the ultimate fireworks show, which would leave us with a star brighter than the full moon that’s visible even in daylight. And who doesn’t want to see something like that?

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