Sound recording and playback have come a long way in the last century or so, but it’s fair to say there’s still a lot of interesting stuff locked away on old recordings. Not having a way to play it back is partly to blame; finding an antique phonograph that plays old-timey cylinder recordings is pretty hard. But even then, how do you digitize the output of these fragile, scratchy old recordings?
As it happens, [Jan Derogee] is in a position to answer these questions, with an antique phonograph and a bunch of Edison-style wax cylinders with voices and music from a bygone era locked away on them. It would be easy enough to just use the “reproducer” he previously built and set up a microphone to record the sound directly from the phonograph’s trumpet, but [Jan] decided to engineer a better solution. By adding the piezo element from an electronic greeting card to his reproducer, potted with liberal quantities of epoxy and padded with cotton, the piezo pickup was attached to the phonograph arm in place of the original stylus and trumpet. The signal from the piezo element was strong enough to require a shunt resistor, allowing it to be plugged directly into the audio input jack on a computer. From there it’s just an Audacity exercise, plus dealing with the occasional skipped groove.
We appreciate [Jan]’s effort to preserve these recordings, as well as the chance to hear some voices from the past. We’re actually surprised the recording sound as good as they do after all this time — they must have been well cared for.
There’s no doubting the utility of the trusty solderless breadboard, but you have to admit they’re less than perfect. They’re not ideal for certain types of circuits, of course, but that’s less of a problem than those jumper wires. The careless will end up with their components hopeless tangled in a rat’s nest of jumpers, while the fastidious will spend far more time making the jumpers neat and tidy than actually prototyping the circuit itself. What to do?
One way to crack this nut is to make the solderless breadboard jumperless, too. That’s the idea behind “breadWare” a work-in-progress undertaken by [Kevin Santo Cappuccio]. The idea is to adapt a standard breadboard so that connections between arbitrary pairs of common contact strips — plus the power rails — can be made in software. The trick behind this is a matrix of analog CMOS switch chips, specifically the MT8816AP. Each chip’s 128 crosspoint switches can handle up ± 12 volts, so there are plenty of circuits that can use these programmable silicon jumpers.
[Kevin] is currently on version 0.2, which is sized to fit under a solderless breadboard and make a compact package. He shared details on how he’s connecting to the breadboard contacts, and it looks like a painful process: pull out the contact, cut a small tab at the gutter-end, and bend it down so it forms a lead for a through-hole in the PCB. It seems like a lot of work, and there must be a better way; [Kevin] is clearly open to suggestions.
Raise your hand if you remember when PulseAudio was famous for breaking audio on Linux for everyone. For quite a few years, the standard answer for any audio problem on Linux was to uninstall PulseAudio, and just use ALSA. It’s probably the case that a number of distros switched to Pulse before it was quite ready. My experience was that after a couple years of fixing bugs, the experience got to be quite stable and useful. PulseAudio brought some really nice features to Linux, like moving sound streams between devices and dynamically resampling streams as needed.
The earliest televisions used a spinning disk technology called the Nipkow disk, which is exactly what [Science ‘n’ Stuff] recreated with their Arduino-based mechanical color television (video link, also embedded below.) The device reads video and audio from an SD card, and displays the video using a precisely-timed RGB LED visible through a perforated spinning disk. The persistence of vision effect results in a video that is small, relative to the size of the disk, but perfectly watchable. A twist is that the video is in color!
A Nipkow disk is a fairly simple and electromechanical device that relies on timing; something a modern microcontroller and RGB LED is perfectly capable of delivering. In this device, the holes in the disk create 32 vertical scanlines with 96 “pixels” making up each of those lines. Spinning disk technology was always limited to being monochromatic, but in this implementation, each “pixel” is given its own unique color by adjusting the RGB LED accordingly.
The first video shows off the device and demonstrates it working; note that it may look like there are multiple little screens, but the center one can be thought of as the “true” display with the others essentially being artifacts due to light leakage. If you’re interested in the nuts and bolts of exactly how a Nipkow disk works, then the second video is what you’ll be more interested in, because it goes through all the details of exactly how everything functions.
After decades of improvements to hard disk drive (HDD) technology, manufacturers are now close to taking the next big leap that will boost storage density to new levels. Using laser-assisted writes, manufacturers like Seagate are projecting 50+ TB HDDs by 2026 and 120+ TB HDDs after 2030. One part of the secret recipe is heat-assisted magnetic recording (HAMR).
One of the hurdles with implementing HAMR is finding a protective coating for the magnetic media that can handle this frequent heating while also being thinner than current coatings, so that the head can move even closer to the surface. According to a recent paper by N. Dwivedi et al. published in Nature Communications, this new protective coating may have been found in the form of sheets of graphene.
With the market for STM32F103C8-based ‘Blue Pill’ boards slowly being overrun with boards that contain either a cloned, fake or outright broken chip, [Terry Porter] really wanted to have an easy, automated way to quickly detect whether a new board contains genuine STM32 silicon, or some fake that tries to look the part. After more than a year of work, the Blue Pill Diagnostics project is now ready for prime time.
We have covered those clone MCUs previously. It’s clear that some of those ‘Blue Pill’ boards obviously do not have a genuine STM32 MCU on them, as they do not have the STM32 markings on them, while others fake those markings on the package and identifying can be hard to impossible. Often only testing the MCU’s actual functionality can give clarity on whether it’s a real STM32 MCU.
These diagnostics allow one to test not only the 64 kB of Flash, but also the 64 kB of ‘hidden’ Flash that’s often found on these MCUs (rebadged 128 kB STM32F103 cores). It further checks the manufacturer JDEC code and uses a silicon bug in genuine STM32F1xx MCUs where the BGMCU_IDCODE cannot be read without either SWD or JTAG connected.
Another interesting feature of Blue Pill Diagnostics is using Mecrisp-Stellaris Forth as its foundation, which allows for easy access to a Forth shell via this firmware as well, not unlike MicroPython and Lua, only in a fraction of the Flash required by those. We have previously written about using Mecrisp-Stellaris in your projects.
[Rowan Patterson] informed us about a recent ticket he opened over at the Raspberry Pi Documentation GitHub repository. He asked about the the lack of updates to the Raspberry Pi 4’s USB-C power schematics for this board. You may recall that the USB-C power issue was covered by us back in July of 2019, yet the current official Raspberry Pi 4 schematics still show the flawed implementation, with the shorted CC pins, nearly two years later.
[Alasdair Allan], responsible for the Raspberry Pi documentation, mentioned that they’re in the process of moving their documentation from Markdown to AsciiDoc, and said that they wouldn’t have time for new changes until that was done. But then [James Hughes], Principal Software Engineer at Raspberry Pi, mentioned that the schematics may not be updated even after this change due to a of lack of manpower.
As [James] emphasized, their hardware will probably never be open, due to NDAs signed with Broadcom. The compromise solution has always been to publish limited peripheral schematics. Yet now even those limited schematics may not keep up with board revisions.
An easy fix for the Raspberry Pi 4’s schematics would be for someone in the community to reverse-engineer the exact changes made to the Raspberry Pi 4 board layout and mark these up in a revised schematic. This should be little more than the addition of a second 5.1 kΩ resistor, so that CC1 and CC2 each are connected to ground via their own resistor, instead of being shorted together.
Still, you might wish that Raspberry Pi would update the schematics for you, especially since they have updated versions internally. But the NDAs force them to duplicate their efforts, and at least right now that means that their public schematics do not reflect the reality of their hardware.