Random Access Memory From A Rotating Drum In A Bendix G15

August 22, 2023 by 28 Comments

When it’s the 1950s and you are tasked to design a computer system that features not only CPU registers but also a certain amount of RAM, you do not have a lot of options. At this point in time, discrete logic was the rule, and magnetic core memory still fairly new and rather expensive. This is where the rotating drum comes in, which is somewhat like a cross between an old-style cylinder record and a hard drive. In a recent [Usagi Electric] video, a 1950s Bendix G15 system is demonstrated, which features such a rotating drum device, alongside both tube-based circuits and newfangled diode-based circuitry.

Simplified diagram of a rotating drum random access memory unit, showing the read-erase-write process as the drum spins.
Simplified diagram of a rotating drum random access memory unit, showing the read-erase-write process as the drum spins.

This particular unit was borrowed from the System Source museum, with the intent to restore it to a working condition. Part of this process involved figuring out the circuitry, which was made easy by the circuit schematic drawings that came with the original machine. According to the official brochure by the manufacturer, the ‘short lines’ that are intended for the CPU registers, the access time was less than 1 millisecond, which is pretty darn fast considering the era and the discrete CPU’s clock speed.

For the drum itself, however, popping the cover off the unit showed that it had suffered some damage that had resulted in the multiple heads contacting the surface. Despite this disappointment, it’s not the end of the restoration, however. The museum has one more Bendix G15 standing around, with a rotating drum unit that looks to be in mint condition. The damaged magnetic coating on the other rotating drum may conceivably be resurfaced, which if successful could provide new hope to a lot of retro systems out there that also use magnetic media, whether in drum or disk format.

Continue reading “Random Access Memory From A Rotating Drum In A Bendix G15” →

Where Did Your PCB Go Wrong? KiRI Knows

August 21, 2023 by 5 Comments

When working on a PCB design in KiCad, it’s helpful that the files are all text and can easily be checked into Git or other source control. However, stepping back through the revisions to determine where precisely a trace got routed wrong can be tricky. [Leandro] started with a simple script that exported the KiCad project to an image for inspection — over time it grew into a full-blown visual diff tool named KiCad Revision Inspector (KiRI).

The primary mechanism exports the revisions of a KiCad 5, 6, or 7 project to SVG, which can then be compared via a handy onion skin view. As this is a tool written for those using KiCad, shortcuts are a huge part of the experience. A command line interface generates artifacts to view the diff in any web browser. As these outputs have the KiRI tooling baked in, it is relatively easy to archive the output as a build artifact and allow easy access to review design changes.

For the long-time reader, you might remember back in 2018 talked about another diffing tool called plotgitsch (which this KiRI uses for KiCad 5 projects). KiCad has grown significantly in the last five years. It might be time to update our tips to utilize Git better for your PCB designs.

Continue reading “Where Did Your PCB Go Wrong? KiRI Knows” →

Debian Buzz (1.1) running under Bochs. (Credit: Thomas Stewart)

Looking Back On 30 Years Of Debian

August 21, 2023 by 18 Comments

The early history of Linux is a rather murky period to most, long before the era of glitzy marketing and proclamations of ‘the Linux desktop’ being the next hot thing. This was also the era when the first Linux distributions were born, as the Linux kernel never came as a whole OS package – unlike the BSDs – which necessitated others to package it with the elements that make up kernel and user space, such as the GNU tools.

One of these original distributions was Debian, which this month celebrates its 30th birthday. Its entire history, starting with the initial 0.01 release is covered in great detail on the Debian website. After the first release of the Linux kernel in 1991, it would take until August of 1993 when [Ian Murdock] embarked on the Debian project, sponsored by the GNU Project of the Free Software Foundation. This was a pretty rough period, with much of 1994 spent figuring out the basics of the system, the package manager and establishing a release system. Continue reading “Looking Back On 30 Years Of Debian” →

A Mainframe Computer For The Modern Age

August 21, 2023 by 50 Comments

The era of mainframe computers and directly programming machines with switches is long past, but plenty of us look back on that era with a certain nostalgia. Getting that close to the hardware and knowing precisely what’s going on is becoming a little bit of a lost art. That’s why [Phil] took it upon himself to build this homage to the mainframe computer of the 70s, which all but disappeared when PCs and microcontrollers took over the scene decades ago.

The machine, known as PlasMa, is not a recreation of any specific computer but instead looks to recreate the feel of computers of this era in a more manageable size. [Phil] built the entire machine from scratch, and it can be programmed directly using toggle switches to input values into registers and memory. Programs can be run or single-stepped, and breakpoints can be set for debugging. The internal workings of the machine, including the program counter, instruction register, accumulator, and work registers, are visible in binary lights. Front panel switches let you control those same items.

The computer also hosts three different microcodes, each providing a unique instruction set. Two are based on computers from Princeton, Toy-A, and Toy-B, used as teaching tools. The third is a more advanced instruction set that allows using things like emulated peripherals, including storage devices. If you want to build one or just follow along as the machine is constructed, programmed, and used, [Phil] has a series of videos demonstrating its functionality, and he’s made everything open-source for those more curious. It’s a great way to get a grasp on the fundamentals of computing, and the only way we could think of to get even more into the inner workings of a machine like this is to build something like a relay computer.

Continue reading “A Mainframe Computer For The Modern Age” →

An Effects Pedal For Keyboards (and Mice)

August 21, 2023 by 4 Comments

Effects pedals for musical instruments like electric guitars can really expand a musician’s range with the instrument. Adding things like distortion, echo, and reverb at the push of a button can really transform the sound of a guitar and add depth to a performance. But [Guy] wondered why these effects should be limited to analog signals such as those from musical instruments, and set about to apply a number of effects to the use of computer keyboards and mice with this HID effects pedal.

The mouse is perhaps the closer of the two to an analog device, so the translations from the effects pedal are somewhat intuitive. Reverb causes movements in the mouse to take a little bit of extra time before coming to a stop, which gives it the effect of “coasting”. Distortion can add randomness to the overall mouse movements, but it can also be turned down and even reversed, acting instead as a noise filter and smoothing out mouse movements. There’s also a looper, which can replay mouse movements indefinitely and a crossover, which allows the mouse to act as a keyboard.

For the keyboard, included effects are a tremolo, which modulates between upper- and lower-case at certain intervals; echo, which repeats keypresses; and a pitch-shift which outputs a “higher” character in the alphabet above whichever one has been pressed. Like the mouse, there’s also a crossover mode which allows the keyboard to be used as a mouse.

The device looks and feels like an effects pedal for a guitar would, with a RP2040 inside to intercept HID information, do the signal processing, and then output the result to the computer. And, while [Guy] admits this was a fun project with not many practical uses, there are a couple handy ones including potentially the distortion effect to smooth out mouse inputs for those with neuromuscular disorders or the mouse looper to act as a mouse jiggler for those with micromanaging employers. It’s also reprogrammable, and as we’ve seen since time immemorial having a programmable foot keyboard can be extremely handy for certain workflows.

Continue reading “An Effects Pedal For Keyboards (and Mice)” →

2023 Hackaday Prize: Two Bee Or More Bee Swarm Detection

August 21, 2023 by 6 Comments

In the bustling world of bees, swarming is the ultimate game of real estate shuffle. When a hive gets too crowded or craves a change of scenery, colonies scout out swarms for a new hive. [Captain Flatus O’Flaherty] is a beekeeper trying to capture more native honey bees, and a custom LoRa-enabled capture hive helps him do that.

A catch hive, perched high and mighty, lures scouting as potential new homes. If selected, a swarm of over a thousand bees can move in, where [Flatus]’s detector comes in. Many catch hives are scattered around, and manually checking them is difficult. While the breath of one bee is hard to see, a thousand bees produce enough CO2 to be detected by a sensor. A custom PCB with a solar-powered  +30dB LoRa radio measures CO2 and reports back. The PCB contains an ESP32 D4 and a 1-watt Ebyte E22-400M30S LoRa module. If the CO2 levels are still elevated at nightfall, [Flatus] can be pretty confident a swarm has moved in.

Using the data collected, he massaged it to create a dataset suitable for training on XGBoost. With weather data and other conditions, the model tries to predict when a swarm is more or less likely to happen. Apis Mellifera (the local honeybee around [Flatus]) loves sun-kissed, warm, humid afternoons with little wind.

We’ve seen beehive monitors before and love exploring what the data could be used for—video after the break.

Continue reading “2023 Hackaday Prize: Two Bee Or More Bee Swarm Detection” →

A Soyuz-2.1b rocket booster with a Fregat upper stage and the Luna 25 lunar lander blasts off from a launchpad at the Vostochny Cosmodrome in Amur Oblast, Russia.

Luna 25’s Demise: Raising Fundamental Questions About Russia’s Space Program

August 21, 2023 by 79 Comments

The recent news that Russia’s Luna 25 Moon lander had made an unexpected lithobraking detour into the Moon’s surface, rather than the expected soft touchdown was met by a variety of responses, ranging from dismay to outright glee, much of it on account of current geopolitical considerations. Yet politics aside, the failure of this mission casts another shadow on the prospects of Russia’s attempts to revive the Soviet space program after a string of failures, including its ill-fated Mars 96 and Fobos-Grunt Mars missions, the latter of which also destroyed China’s first Mars orbiter (Yinghuo-1) and ignited China’s independent Mars program.

To this day, only three nations have managed to land on the Moon in a controlled fashion: the US, China, and the Soviet Union. India may soon join this illustrious list if its Chandrayaan-3 mission’s Vikram lander dodges the many pitfalls of soft touchdowns on the Moon’s surface. While Roscosmos has already started internal investigation, it does cast significant doubt on the viability of the Russian Luna-Glob (‘Lunar Sphere’) lunar exploration program.

Will Russia manage to pick up where the Soviet Union left off in 1976 with the Luna 24 lunar sample return mission?

Continue reading “Luna 25’s Demise: Raising Fundamental Questions About Russia’s Space Program” →