Swapped ROM Revives Ailing HP-48S Calculator

June 9, 2022 by Tom Nardi 10 Comments

Buying broken gear for cheap is time honored hacker tradition, and while we might not always be successful in reviving it, rarely do we come away empty handed. There’s always parts to salvage, and you can’t put a price on the knowledge to be gained when poking around inside an interesting piece of hardware. So we’re not surprised at all to hear that [Tomas Pavlovic] jumped at the chance to grab this faulty HP-48S calculator for a couple bucks.

Luckily for us, the story doesn’t end at the bottom of his parts bin. When he got the HP-48S back home, he immediately set out to see if it could be repaired. After changing out a few choice components and not seeing any result in the device’s behavior, he became suspicious that the problem may be with the firmware; specifically, the soldered-on chip that holds it.

After carefully lifting the NEC uPD23C2000GC from its resting place for the last 30 years or so, he wired up an adapter that let him connect the chip to his programmer so its contents could be dumped. Rather than trying to find another ROM chip, he decided to wire in a socket and found a re-writable SST39SF040 that could stand in as a replacement. Flashing a fresh copy of the firmware to the new socketed chip got the calculator up and running again, with the added bonus of allowing [Tomas] to pull the chip and flash a different firmware version should he care to experiment a bit.

Now, we know what you’re thinking. Where was the fix? What exactly brought this piece of 1990s gear back to life? That part, unfortunately, isn’t very clear. You’d think if the original ROM chip was somehow faulty, [Tomas] wouldn’t have been able to so easily pull a valid firmware image from it. That leaves us with some pretty mundane possibilities, such as a bad solder joint on the chip’s pins. If that was indeed the case, this fix could have been as simple as running a hot iron over the pins…but of course, where’s the fun in that?

Update: We heard back from [Tomas], and it turns out that when compared to a known good copy, the dumped firmware did have a few swapped bits. His theory is that the NEC chip is in some weird failure mode where the calculator wouldn’t run, but it was still functional enough to get most of the content off of it. What do you think? Let us know in the comments.

The Case For Designer Landline Phones

June 9, 2022 by Kristina Panos 34 Comments

Long before the idea of hot dog-shaped iPhone cases, Otter Boxen, or even those swappable Nokia face plates, people were just as likely to express themselves with their landline phones. Growing up at my house in the 80s, the Slimline on the kitchen wall was hidden inside a magneto wall set from the early 1900s, the front of which swung out to reveal the modern equipment behind it. Back in my bedroom, I had the coolest phone ever, a see-through Unisonic with candy-colored guts. Down in the basement was my favorite extension, tactility-wise: a candy apple-red wall unit with dimly-lit circular push buttons that were springy and spongy and oh-so fun to dial.

Popular culture shows us that people were dreaming of cool telephone enclosures before they were even a thing. Obviously, TV secret agent Maxwell Smart’s shoe phone wasn’t plausible for the technology of that era, but it also wasn’t really feasible for aesthetic reasons. For decades, phone subscribers had to use whatever equipment Ma Bell had to offer, and you couldn’t just buy the things outright at the mall — you had to lease the hardware from her, and pay for the service.

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The Compu-tor Is A Raspberry Pi Laptop In A Mahogany Case

June 9, 2022 by Robin Kearey 21 Comments

The Compu-tor, designed by [Henry Edwards], is one of those things that doesn’t neatly fit into any categories. It is a clamshell-type portable computer, although unlike most laptops, it doesn’t come with a built-in battery. It has a sleek custom-designed case, but lacks the futuristic sci-fi looks typical of a cyberdeck. The keyboard can act as an input device, but can also turn into a musical instrument.

In short, it’s a bit of all of those things, but the most striking part is the beautifully-machined mahogany case. The two halves are connected through two beefy friction hinges and a silicone ribbon cable: the bottom half contains the keyboard, speakers, USB ports and power connections, while the top half holds a Raspberry Pi and a 10″ touchscreen. The display bezel has that curved shape typical of CRT monitors, fitting nicely with the 1970s vibe given off by the dark wood.

Another retro touch is in the connections between the various circuit boards and the front panel switches: [Henry] used wire-wrapping, something we haven’t seen for a while. The keyboard is a simple grid of identical keys with handwritten labels. Other labels, like that of the power connector, are made from traditional embossing tape.

The Compu-tor runs Debian, and seems to be quite usable as a compact laptop. It even comes with USB ports to hook up external devices, and with a simple 12 V input it should be no problem to find an external power source for it. Wood seems to be a popular material to build Raspberry Pi-based laptops from: we’ve seen them housed in anything ranging from wooden cigar-boxes to laser-cut plywood, and even incredibly tiny boxes.

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Revolving Doors Aren’t Just Annoying, They’re Energy Saving Too

June 9, 2022 by Lewin Day 43 Comments

While most of us have been content with swing and sliding doors for the vast majority of our needs around the home, the revolving door remains popular in a wide variety of contexts.

It’s a confounding contraption that always feels ready to snatch and ensnare the unwary user. However, these doors do have certain benefits that have allowed them to retain popularity in many public buildings around the world. Let’s dive in to why below.

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Live Floppy Music Adds Elegance To Any Event

June 9, 2022 by Tom Nardi 16 Comments

It wasn’t long after early humans started banging rocks together that somebody in the tribe thought they could improve on things a bit by doing it with a little rhythm. As such the first musician was born, and since it would be a couple million years before humanity figured out how to record sound, musical performances had to be experienced live throughout most of history. On the cosmic scale of things, Spotify only shows up about a zeptosecond before the big bash at midnight.

So its only fitting that [Linus Åkesson] has perfected the musical floppy drive to the point that it can now be played live. We understand the irony of this being demonstrated via the video below the break, but we think it still gets the point across — rather than having to get a whole array of carefully-scripted drives going to perform something that even comes close to a musical number, he’s able to produce tones by manipulating a single drive in real-time.

In his write-up, [Linus] not only goes over the general nuts and bolts of making music with floppy drives, but specifically explains how this Commodore 1541-II drive has been modified for its new life as a digital virtuoso. From his experiments to determine which drive moves corresponded to the most pleasing sounds, to the addition of a small microphone and a piezo sensor paired with an LMC662-based amplifier to provide a high-fidelity capture of the drive’s sounds and vibrations, there’s a lot of valuable info here for anyone else looking to make some sweet tunes with their old gear.

We’ve seen something of a resurgence of the floppy drive this year, with folks like Adafruit digging into the classic storage medium, and an experimental project to allow the Arduino IDE to create bootable x86 floppies. You won’t hear any complaints from us — while they might not offer much capacity compared to more modern tech, there’s something about a stack of multi-colored disks with hastily applied labels that warms our cold robotic hearts.

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A Linux Distribution For DOOM

June 9, 2022 by Bryan Cockfield 40 Comments

If you’ve gone further into the Linux world than the standard desktop distributions like Ubuntu or Fedora, you have undoubtedly come across some more purpose-built distributions. Some examples are Kali for security testing, DragonOS for software-defined radio, or Hannah Montana Linux for certain music fans. Anyone can roll their own Linux distribution with the right tools, including [Shadly], who recently created one which only loads enough software to launch the 1993 classic DOOM.

The distribution is as simple as possible and loads no bloat other than what’s needed to launch the game. It loads the Linux kernel and the standard utilities via BusyBox, then runs fbDOOM, which is a port of the game specifically designed to run on the Linux framebuffer with minimal dependencies. After most of that, the only thing left is to use GRUB to boot the distribution, and in just a moment, Doomguy can start slaying demons. The entire distribution is placed into a bootable ISO file that can be placed on any bootable drive.

As far as DOOM hacks go, we’re used to seeing the game running on hardware it was never intended for like the NES or on an office phone. This one, on the other hand, gives us a little more insight into just how little is needed for a full-fledged Linux distribution, as long as what you need to do is relatively straightforward.

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A Lab-Grade Measurement Microphone For Not A Lot

June 8, 2022 by Jenny List 21 Comments

The quality of any measurement can only be as good as the instrument used to gather it, and for acoustic measurements, finding a good enough instrument can be surprisingly difficult. Commonly available microphones can be of good quality, but since they are invariably designed for speech or music, they need not have the flat or wide enough response and low noise figure demanded of an instrumentation microphone.

Microphones for measurement purposes can be had for a very large outlay, but here’s [Peter Riccardi] with a unit designed around an array of MEMS capsules that delivers comparable performance for a fraction of the cost.

The result is both an extremely interesting project for those of us with an interest in audio, and a thorough delve into some aspects of its design for those who are merely curious. It uses four capsules in an effort to cancel out induced electrical noise, and boasts some impressive comparative measurements when tested against a commercial measurement microphone. We could almost see ourselves building this project.

Interested in audio technology? Try our Know Audio series.