Queen Victoria’s Secret (Teletype And COSMAC Elf)

April 12, 2021 by Al Williams 15 Comments

We don’t really think anyone in the Victorian era had a COSMAC Elf — the homebrew computer based around the RCA 1802 CPU. But if they did, it might have looked like [Daniel Ross’] steampunk recreation of the system that includes an appropriate-looking teletype device. You can see the thing in a series of videos, below. There are actually quite a few videos showing different parts of the system, along with several blog postings stretching back a few months.

A magic eye tube doesn’t look out of place in this build. We especially liked the glass tube displays and the speaker, although we thought the USS Enterprise looked out of place with the technology based on stone knives and bearskins, to paraphrase Mr. Spock. On the plus side, the VFD displays have the right glowing look, although a Nixie would have been pretty good there, too.

The videos don’t have much detail, but the blog posts do if you wanted to attempt something similar. Honestly, 1802 system design is pretty easy thanks to the its on-chip DMA that allows you to load memory from switches with no actual software like a monitor. The teletype started out life as a Remington #7 from around 1900, although another newer machine donated parts to get everything working. It is a testament to how well things were built then that it took as much abuse as it did and still has working parts.

We have a soft spot for the 1802 — it was a very good design for its time. We’ve even gone as far as to simulate it.

Continue reading “Queen Victoria’s Secret (Teletype And COSMAC Elf)” →

Diving Into The Details Of Keyboard Interfaces At The Gate-Level

April 7, 2021 by Dan Maloney 5 Comments

Never doubt the value of a good teacher. Even if you know — or think you know — the material being presented, a good teacher can open your eyes to new ways of looking at things that will pay dividends you never expected.

That’s the feeling we got while watching [Ben Eater]’s latest video on building a keyboard interface (embedded below) for his breadboard 6502 computer. On the face of it, getting a keyboard to talk to a computer should be a simple job. [Ben] had previously looked at the serial protocol used by the old PS/2 keyboard and even built a wildly complex circuit out of discrete shift register chips to visualize the data being sent by the keyboard. The video below continues that work, this time concentrating on using the keyboard with his 6502 breadboard computer.

After some instructive preliminaries on interrupt programming, [Ben] dives into the logic-level details of teasing useful signals from the keyboard. His signal processing starts with some inverters and an RC network to turn multiple clock pulses into one logic level transition. Walking through this circuit step by step was the really interesting bit; even if you know that the answer is eventually going to be “Schmitt trigger,” getting to that point was really instructive.

Of course, what [Ben]’s videos mainly accomplish is making us want to follow along with him and build a breadboard computer of our own. From a low-rez VGA card to a reliable UART, following along with his discrete chip builds is always educational.

Continue reading “Diving Into The Details Of Keyboard Interfaces At The Gate-Level” →

Forgotten Tech — Self Driving Cars

April 6, 2021 by Chris Lott 29 Comments

The notion of self driving cars isn’t new. You might be surprised at the number of such projects dating back to the 1920s. Many of these systems relied on external aids built into the roadways. It’s only recently that self driving cars on existing roadways are becoming closer to reality than fiction — increased computer processing power, smaller and power-efficient computers, compact Lidar and millimeter-wave Radar sensors are but a few enabling technologies. In South Korea, [Prof Min-hong Han] and his team of students took advantage of these technological advances and built an autonomous car which successfully navigated the streets of Seoul in several field trials. A second version subsequently drove itself along the 300 km journey from Seoul to the southern port city Busan. You might think this is boring news, until you realize this was accomplished back in the early 1990s using an Intel 386-powered desktop computer.

The project created a lot of buzz at the time, and was shown at the Daejeon Expo ’93 international exposition. Alas, the government eventually decided to cancel the research program, as it didn’t fit into their focus on heavy industries like ship building and steel production. Given the tremendous focus on self-driving and autonomous vehicles today, and with the benefit of hindsight, we wonder if that was the best choice. This isn’t the only decision from Seoul that seems questionable when viewed from the present — Samsung executives famously declined to buy Andy Rubin’s new operating system for digital cameras and handsets back in late 2004, and a few weeks later Android was purchased by Google.

You should check out [Prof Han]’s YouTube channel showing videos of the car’s camera while operating in various conditions and overlaid with the lane recognition markers and other information. I’ve driven the streets of Seoul, and that alone can be a frightening experience. But [Han] manages to stretch out in the back seat, so confident in his system that he doesn’t even wear a seatbelt.

Continue reading “Forgotten Tech — Self Driving Cars” →

This Vintage LED Matrix Lives In A Gold Bathtub

April 3, 2021 by Donald Papp 9 Comments

Early LED displays came in all sorts of configurations. Because the LED was fairly new technology, all kinds of ideas were getting tried, and with all that work there was plenty of opportunity for hardware that didn’t make the cut to fall into obscurity. That’s exactly what happened to the Hewlett-Packard 5082-7002, a 5×7 LED matrix display with something many of its brethren didn’t: an oversized gold tub to sit in.

It doesn’t seem that these displays were ever used in any actual products, and its origins are a mystery, but the device itself was nevertheless assigned an HP part number. Beyond that, not much is known about them, but [Industrial Alchemy] reminds us that many early LED devices were poorly documented and never produced in any real quantities. They became forgotten hardware, waiting to be rediscovered.

The 5082-7002 has a oversized gold tub that makes the 5×7 LED matrix mounted inside look puny by comparison, and reading any display made from these units would be difficult because the large size of the device would mean a lot of empty space between each character or digit. But it’s definitely got a striking look to it, no doubt about that.

What’s neat is that the 5802-7002 actually showed up in a video we featured with a look back at cool old LED technology. If you would like to (briefly) see the HP 5802-7002 a bit closer under a microscope, here is a link to the video, cued to 2:19.

Smashed Amiga 2000 Gets New Lease On Life

April 2, 2021 by Tom Nardi 9 Comments

For most people, opening up a package and seeing that the Amiga 2000 you purchased on eBay had been smashed up by the delivery carrier would be a heartbreaking moment. But not [Drygol]. If you live and breathe vintage computer restorations like he does, finding your latest acquisition is in need of more repairs and upgrades than you originally anticipated is actually a bonus.

The first issue that needed sorting out was the broken case. This Amiga must have had one wild ride, as there were several nasty cracks in the front panel and whole chunks had been broken off. We’ve seen [Drygol] repair broken computer cases before, but it seems like each time he comes up with some new tricks to bring these massacred pieces of plastic back to like-new condition. In this case plastic welding is used to hold the parts together and fill in the gaps, and then brass mesh is added to the backside for strength. The joints are then sanded, filled in with polyester putty, and finally sprayed with custom color matched paint. While he was in the area, he also filled in a hole the previous owner had made for a toggle switch.

Before

After

Then [Drygol] moved onto the internals. Some of the traces on the PCB had been corroded by a popped battery, a socket needed to be replaced, and as you might expect for a machine of this vintage, all of the electrolytic capacitors were suspect and needed to go. Finally, as the system didn’t have a power supply, he wired in a picoPSU. That got the 34 year old computer back up and running, and at this point, the machine was almost like new again. So naturally, it was time to start with the upgrades and modifications.

[Drygol] added an IDE interface and connected a CompactFlash adapter as the computer’s primary drive. For the secondary, he installed a GoTek floppy drive emulator that lets you replace a mountain of physical disks with a USB flash drive full of images. Between the two, all of the computer’s storage needs are met with nary a moving part.

The emulator was given its own 3D printed front panel to fit with the Amiga’s visual style, and he also printed out a holder for the RGB4ALL S-Video/Composite adapter installed on the rear of the machine. To help keep all this new gear cool, he finished things off with a new case fan.

Some will no doubt complain about the addition of the extra gadgetry, but to those people, we suggest you just focus on the phenomenal case restoration work. While you might not agree with all of the modifications [Drygol] makes, there’s no question that you can learn something by going through his considerable body of work.

Over-Engineered Incandescent Numerical Display Shows Great Workmanship

April 1, 2021 by Donald Papp 18 Comments

Back before LED technology came into its own, displays used incandescent bulbs. These vintage incandescent displays weren’t necessarily big; the Eaton 925H-C fiber optic display, for example, has numbers barely 7 mm tall and packs two of them into a tiny area. Of course, the depth of the display module itself is huge by today’s standards; those components have got to go somewhere, after all.

This particular device is, in [Industrial Alchemy]’s words, “[d]ripping with the spending excess that only a bottomless military budget can provide… the Eaton 925H-C may not be a practical device, but it is certainly an impressive one.”

The way the display works is this: individual incandescent bulbs light up fiber optic light guides, which terminate on the face of the display in small dots to make up a numerical display. With only fourteen bulbs, the dots we see here clearly aren’t individually addressable; the two digits are most likely broken up into seven segments each, with three dots making up each segment.

No expense seems spared in the design and manufacture of these displays. Even the incandescent lamps have individual shock absorbers.

The sheer amount of workmanship in these displays is remarkable, and their design makes them easy to retrofit with LED technology instead of replacing the tiny incandescent lamps. In a stark contrast to all of the machined aluminum and gold plated contacts seen here in the Eaton 925H-C, take a look at this Soviet-era seven-segment incandescent display whose construction is far less sophisticated, but shows off its own clever engineering. We’ve also seen more modern DIY takes on the concept, using LED light sources and cured UV resin light pipes to get that vintage look to the displays.

An Ancient 8 Inch Floppy, With A PC

March 27, 2021 by Jenny List 41 Comments

Most of us may have gratefully abandoned the floppy disk a decade or more since, but even today many PCs and their operating systems retain the ability to deal with these data storage relics. The PC was widely fitted with either 5.25″ or 3.5″ disk drives, but other formats such as the older 8″ discs were not a fixture in the 16-bit desktop computing world. It’s something [Jozef Bogin] has taken aim at, with his exploits in connecting a variety of 8″ drives to a PC.

In the early 1970s there were a variety of different 8″ drive standards that weren’t all entirely compatible, but a de facto standard emerged as clones of the Shuggart drives used by IBM. It’s a modified version of this interface that can be found in a PC floppy controller. While there is enough electrical compatibility to connect the two there remains a variety of connectors used on the drives. There are also a wide range of power supplies, with drives requiring 5, 12, and 24 volts, and some of them even requiring AC mains with different versions for 50Hz and 60Hz mains frequencies.

With an 8″ drive hooked up to a PC, how might DOS, or even older Windows versions, interface with it? To that end he’s created a piece of software called 8format, which not only allows 8″ disks to be formatted for the PC, but also provides a driver that replaces the BIOS floppy settings for these drives. This doesn’t work for imaging disks from other older platforms, but he provides pointers to more capable floppy controllers for that.

If these drives interest you, there’s more to be gleaned from a tale of interfacing them with 8-bit retrocomputers.