[Mike] from Leaded Solder has a soft spot for old computers, and a chance encounter with a friend sent them deep down the deep hole that is the world of 80s and 90s-era Japanese home computers. Many people playing with these machines have all kinds of issues to deal with, such as rotting cartridges, failing components, and just dirt and mank in critical places. [Mike] decided that working on an MSX-standard custom programmable cartridge would be sensible, but then got stuck on how the MSX cartridge mapping works.
The Konami 128K scheme uses 4 to 4-of-8 mapping.
You may recall that the MSX platform is not a single computer but a standard to which many (mainly Japanese) manufacturers designed their products. This disconnected the software writers from the hardware makers and is essentially a mirror of the IBM-PC clone scene.

The MSX is based around the Z80, which has a 16-bit address bus, restricting it to 64K of ROM or RAM. The MSX has two cartridge slots, an ‘internal’ slot for the BIOS and RAM and a fourth for ‘misc’ use. Each of these is mapped internally into the physical address space. The cartridge slots have 64K of addressable space mapped into the Z80 physical space.

If this was not complicated enough, many MSX games and applications exceeded this restriction and added a layer of mapping inside the cartridge using bank switching. A register in the cartridge could change the upper bits of the address allowing ROMs larger than 64K.

[Mike] wanted to replicate the method Konami used for their games. Their first target was The Maze of Galious, which requires a 128K ROM. Their scheme requires additional hardware to map each of the four 16K slots in the cartridge interface to four of the eight 16K slots of the ROM chip. The game selects which bits of the ROM it needs as the game progresses. The implementation uses an old 74LS670, which can still be bought from old stock as a 4×4 bit register file and a two-way dip selector switch. This allowed [Mike] to fit four games into a single SST39SF040 4MBit parallel flash chip. After a few false starts with the details of address bit selection, they were rewarded by Galious booting up without any additional work needed. If you own an MSX-compatible machine and want to build one for yourself, the full KiCAD project is available on the project GitHub page.

The MSX isn’t a well-known platform in the West, and MSX hacks are a rarity here, but in the spirit of retro, here’s a hack to add support for a retro gamepad to the MSX. Also, if you can’t find a period MSX, you can always build one.

hackaday.com/2024/09/07/buildi…

Although we generally assume that opacity is the normal look for animals like us humans, this factoid is only correct for as long as you maintain the dissimilar optical refraction indices of skin and the more aqueous underlying structures. What if you could change the refraction index of skin? If you could prevent the normal scattering at the interface, you could reveal the structures underneath, effectively rendering skin transparent. [Zihao Uo] and others demonstrate this in a paper published in Science.

The substance they used was the common food dye known as tartrazine, which also goes by the names of Yellow 5 and E102 when it is used in food (like Doritos), cosmetics, and drugs. By rubbing the tartrazine into the skin of mice, the researchers were able to observe underlying blood vessels and muscles. Simulations predicted that the dye would change the refraction index mismatch between lipids and water which normally causes the light scattering that creates the skin’s opaque appearance. With the dye rubbed into the skin, the effect worked to a depth of about 3 mm, which makes it useful for some research and possible medical applications, but not quite at the ‘jellyfish-transparency’ levels that some seem to have imagined at the news.

Researchers and medical personnel have long wished for this kind of in vivo tissue transparency. A 2019 review article by [Mikhail Inyushin] and colleagues in Molecules provides an overview of the many possible ways, both genetic and chemical, that you might see through skin. Tartrazine has a significant advantage: it is generally considered to be a harmless food dye. In addition, reversing the effect is as simple as washing the dye off.

Naturally, human skin will be trickier than that of mice due to the varying presence of melanin. So it will take more work to use this technique on people, but there are many mice and other common lab test critters who are breathing a deep sigh of relief as the scalpel can be put away for some types of studies.

For now, better to stick with MRI. And fair warning: there’s no need to rush out to rub Doritos on your PCB — it doesn’t work.

hackaday.com/2024/09/07/render…

While version control used to be reserved for big corporate projects, it is very mainstream these days. You can attribute much of that to Git, the software that has nearly displaced other version control. Git works well, it is versatile, and it scales well. It is easy to use as an individual developer or as part of a worldwide team. But Git is also one of those things that people don’t always study, they just sort of “pick it up” as they go. That motivated [Glasskube] to create “The Guide to Git I Never Had.”

If you are ready to click away because you are not a software person, hang on. Git is actually useful for many different kinds of data, and there are a number of hardware projects that use Git in some form. That’s especially true if the project has some code associated with it, but there are projects that consist of PCBs, reverse engineering documentation, or schematics.

Simplistically, Git tracks a bunch of files and lets you rewind in time to answer the question: what did this look like a month ago? Or a year ago? However, the real power lies in producing and merging branches.

For example, you might be working on a product and decided to add feature “A.” Meanwhile, your partner decides to work on feature “B.” No problem. You can each work in your own separate branch and get everything working. You don’t even have to be connected to a server until the very end.

When either of you are ready, you can merge your branch with the main branch. Often, this can be done automatically, but Git knows when it is in over its head and will ask for help. When you are both done merging, both of your changes are “live.” If you do it right, Git can also help answer the question: why did we make that change two years ago? It is surprising how often that’s important.

If you think Git is just for code, we can show you some strange examples. If you don’t fancy reading a blog post to learn Git, would you like to play a game?

hackaday.com/2024/09/07/get-th…

Whenever you buy a servo, it usually comes with a little baggie full of various plastic horns. Most of us pick our favorite and use it in our projects. Some of us hack them up, glue them back together, and do all kinds of weird things with them. And others skip them entirely, going for direct drive instead. In a new video, [Dynamix Systems] explores when going direct drive is the right solution.

The video primarily concerns servos as they’re used in the context of aero modeling. In this regard, the video points out that while stock servo horns are easy to use, they can be cumbersome and clumsy. For example, you often end up with horns and control linkages protruding out into the airstream, adding drag and generally making things a bit inelegant. They can also snag on things and easily damage your servos or controls.

Using direct shaft couplers can be a much tidier solution in some respects. The servo can be coupled directly to the axis of motion, allowing it to be hidden inside a wing or tail surface. It can require a little more finesse in installation and design, but they’re much less likely to snag on things or be damaged. There’s also a drag benefit if you do it right. [Dynamix Systems] notes that you’ll want to source some shaft couplers to do this properly, which you can make yourself or buy online fairly easily.

It’s great to see how tidy direct drive really is. We’ve seen some other nifty servo tricks of late, too. Video after the break.

youtube.com/embed/zr02G2yCvGU?…

hackaday.com/2024/09/07/should…

My sister is a beekeeper, or maybe a meta-beekeper. She ends up making more money by breeding and selling new queen bees to other beekeepers than she does by selling honey, but that doesn’t mean that she doesn’t also process the sweet stuff from time to time. She got a free steam-heated oscillating hot knife, used for cutting the waxy caps off of the tops of the cells before spinning the combs down to extract honey, and she thought it might be easier to use than her trusty hand-held electric hot knife.

The oscillating knife, which was built something like a century ago, hadn’t been used in decades. All of the grease had turned to glue, and the large v-belt wheel that made it go was hard to turn by hand, and the motor was missing anyway. So she gave it to my father and me as a project. How could we resist?

We found the original manual on the Internet, which said that it would run from any 1/2 hp motor, or could be optionally driven by a takeoff wheel from a tractor – unfortunately not an option in my sister’s honey house. But we did find a 3/4 hp bench grinder at Harbor Freight that conveniently fit inside the case, and bought the smallest v-belt pulley wheel that would fit the grinder’s arbor. We thought we were geniuses, but when we hooked it all up, it just stalled.

We spent more than a few hours taking the mechanism apart. It was basically an eccentric shaft with a bearing on the end, and the bearing ran back and forth in the groove of a sliding mechanism that the knife blade attached to. As mentioned above, everything was gunked, so we took it all apart. The bearing was seized, so we freed that up by getting the sand out of the balls. The bearing couldn’t move freely in the slide either, but we filed that down until it just moved freely without noticeable play. We added grease from this century, and reassembled it. It turned fine by hand.

But with the belt and motor attached, the mechanism still had just enough friction to stall out the motor. Of course we wrapped some rope around the shaft and pull-started it, and it made a hell of a racket, nearly vibrated itself off the table, and we could see that the marvelous zinc-coated frame that held it all together was racking under the tension. It would require a wholly new housing to be viable, and we hadn’t even figured out a source of steam to heat the knife.

In short, it was more trouble than it was worth. So we packed up the bench grinder in the original container, and returned it no-worse-for-wear to the Freight. But frankly, we had a fantastic time playing around with a noble machine from a long-gone past. We got it “working” even if that state was unworkable, and we were only out the cost of the small v-belt pulley. Who says all of your projects have to be a success to be fun?

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hackaday.com/2024/09/07/fun-an…