Want to learn the internals of the Linux kernel? Version 6.5-rc5 has about 36 million lines of code in it, so good luck! [Seiya] has a different approach. Go back to the beginning and examine the 0.01 version of the kernel. Now you are talking about 10,000 lines and, removing comments and blanks, way less.
Sure, some things have changed, but the core ideas are the same. [Seiya] reports, “Reading V0.01 was really for me. It was like visiting Computer History Museum in Mountainview…”
The new hotness in cheap radios this year has been the Quansheng UV-K5, a Chinese handheld transceiver with significant RF abilities and easy modding. The amateur radio community have seized upon it with glee and already reverse-engineered much of the firmware, but flashing the thing has always required a minor effort. Now thanks to the work of [whosmatt], it can be flashed with little more than a web browser and a serial cable.
This feat was made possible through the magic of WebSerial, a handy feature that allows web applications to talk to connected hardware. We’ve seen it in action a few times in the world of badges, and as browser support for it has improved it’s now available through browsers on all the major platforms.
The web app allows tweaking of the Quansheng settings and will, no doubt, be capable of uploading that when fully open-source firmware is available. It should be of great interest well beyond the world of Chinese radios, though, because we’re guessing there are a lot of projects that could benefit from such a ubiquitous interface tool.
Remember that time when the entire physics community dropped what it was doing to replicate the extraordinary claim that a room-temperature semiconductor had been discovered? We sure do, and if it seems like it was just yesterday, it’s probably because it pretty much was. The news of LK-99, a copper-modified lead apatite compound, hit at the end of July; now, barely three weeks later, comes news that not only is LK-99 not a superconductor, but that its resistivity at room temperature is about a billion times higher than copper. For anyone who rode the “cold fusion” hype train back in the late 1980s, LK-99 had a bit of code smell on it from the start. We figured we’d sit back and let science do what science does, and sure enough, the extraordinary claim seems not to be able to muster the kind of extraordinary evidence it needs to support it — with the significant caveat that a lot of the debunking papers –and indeed the original paper on LK-99 — seem still to be just preprints, and have not been peer-reviewed yet.
So what does all this mean? Sadly, probably not much. Despite the overwrought popular media coverage, a true room-temperature and pressure superconductor was probably not going to save the world, at least not right away. The indispensable Asianometry channel on YouTube did a great video on this. As always, his focus is on the semiconductor industry, so his analysis has to be viewed through that lens. He argues that room-temperature superconductors wouldn’t make much difference in semiconductors because the place where they’d most likely be employed, the interconnects on chips, will still have inductance and capacitance even if their resistance is zero. That doesn’t mean room-temperature superconductors wouldn’t be a great thing to have, of course; seems like they’d be revolutionary for power transmission if nothing else. But not so much for semiconductors, and certainly not today.
[JR] over at [Tech Throwback] got ahold of an unusual piece of gear recently — a portable Point of Sale (POS) credit card machine from the late 1990s (video, embedded below the break ). Today these machines can be just a small accessory that works in conjunction with your smart phone, but only the most dedicated merchants would lug this behemoth around. The unit is basically a Motorola bag phone, a credit card scanner, a receipt printer, a lead-acid battery, and a couple of PCBs crammed into a custom carrying case
Despite having a lot of documentation, [JR] struggles to find any information on this U.S. Wireless POS-50. He finds that the credit card scanner is an Omron CAT-95 authorization terminal, and the Motorola SCN-2397B phone appears to come from the Soft-PAK series.
He is able to power it up, but can’t do much with is because he is missing the authorization password. But regardless, with the demise of the Advanced Mobile Phone System for over a decade, this 850 MHz band analog phone can’t connect to the network anymore.
If you happen to know anything about this old POS, or used a similar luggable system for accepting credit cards in the 1990s, let us know in the comments below.
Measure twice, cut once is excellent advice when building anything, from carpentry to metalworking. While this adage will certainly save a lot of headache, mistakes, and wasted material, it will only get you part of the way to constructing something that is true and square, whether that’s building a shelf, a piece of furniture, or an entire house. [PliskinAJ] demonstrates a few techniques to making things like this as square as possible, in all three dimensions.
The first method for squaring a workpiece is one most of us are familiar with, which is measuring the diagonals. This can be done with measuring tape or string and ensures that if the diagonals are equal lengths, the workpiece is square. That only gets it situated in two dimensions, though. To ensure it’s not saddle-shaped or twisted, a little more effort is required. [PliskinAJ] is focused more on welding so his solutions involve making sure the welding tables are perfectly flat and level. For larger workpieces it’s also not good enough to assume the floor is flat, either, and the solution here is to minimize the amount of contact it has with the surface by using something like jack stands or other adjustable supports.
There are a few other tips in this guide, including the use of strategic tack welds to act as pivot points and, of course, selecting good stock to build from in the first place, whether that’s lumber or metal. Good design is a factor as well. We’ve also featured a few other articles on accuracy and precision,
For organic semiconductors like the very common organic light-emitting diode (OLED), the issue of degradation due to contaminants that act as charge traps is a major problem. During the development of OLEDs, this was very pronounced in the difference between the different colors and the bandgap which they operated in. Due to blue OLEDs especially being sensitive to these charge traps, it still is the OLED type that degrades the quickest as contaminants like oxygen affect it the strongest. Recent research published in Nature Materials from researchers at the Max Planck Institute for Polymer Research by Oskar Sachnik and colleagues (press release) may however have found a way to shield the electron-carrying parts of organic semiconductors from such contaminants.
In current organic semiconductors TPBi is used for electron transport, whereas for this research triazine (Trz, as electron acceptor) and carbozole (Cz, as donor) were used and compared with the properties of leading-edge TPBi. While a few other formulations in the study did not show remarkable results, one compound (3CzTrz) was found using X-ray diffraction (XRD) to have a structure as shown on the right in the heading image, with the carbozole (in blue) forming essentially channels along which electrons can move, while shielded from contaminants by the triazine.
Using this research it might be possible to create organic semiconductors in the future which are free of charge-traps, and both efficiency and longevity of this type of semiconductor (including OLEDs and perovskites) can be improved immensely.
For a variety of reasons revealed in the video below, [Anders Nielsen] use the SST39SF010, a Flash ROM in a 32-pin DIP, in place of the old standby W27C512, an EEPROM in a 28-pin DIP. To deal with those pesky extra pins on the Flash ROM, [Anders] dug into the data sheets and found that thanks to JEDEC standards, almost everything about the pinouts of the two chips is identical. The only real difference is the location of Vcc, plus the presence of a 16th address bus line on the more capacious Flash ROM.
Willing to sacrifice the upper half of the Flash chip’s capacity, [Anders] set about bodging the 32-pin chip to work in a 28-pin socket. The mods include a jumper from pin 32 to pin 30 on the Flash chip, which puts Vcc in the right place, and adding a couple of pull-up resistors for write-enable and A16. Easy enough changes, but unfortunately, [Anders] chose a Flash ROM with heavily oxidized pins, leading to some cold solder joints and intermittent problems while testing. There’s also the fact that not all boards have room for overhanging pins, a problem solved by adding a socket to create a little vertical clearance.