A Straightforward Old-Fashioned DAC

With modern microcontrollers, the process of interfacing with the analogue world is easy. Simply enable the on-board DAC or ADC, and talk to the world. If you’ve ever done this with a slightly older microprocessor, you might have encountered the DAC and ADC as chips in their own right, but how about the earliest generation of microprocessors? In those days, if an analogue component was needed, the circuit which would later be integrated on chip would have to be made from scratch. So it is that [Florian Wilhelm Dirnberger] has built a very old-style 6-bit DAC, using a circuit that would have been familiar back in the early 1970s.

At its heart are a pair of 4007 triple CMOS inverters, which form the six bits driving a resistor ladder DAC. This is simply a chair of R… 2R resistors, relying on Ohm’s law for its operation. Each successive bit contributes twice the current to the output of its predecessor, and the 4007 simply provides a buffered supply for the bits.

It’s the simplest of DACs, if not the most capable. Back in the day a typical ADC might also use this circuit, feeding a comparator alongside the input voltage. The microprocessor would count through the digital values until the comparator output bit flipped, at which point it would take the counter value as the analogue measure. You may never need to build one when your microcontroller has one built in, but it’s useful to know how simple DACs and ADCs work.

If the subject interests you, we’ve had a look at DACs including resistor ladders used in audio.

An art deco style computer made of several grey/blue boxes with silver grates on top of a maple platform.

Clean Slate Is A Vintage Amplifier-Inspired PC

Hacks that bring a vintage flair to modern electronics never get old, and [Jeffrey Stephenson] delivers with his Project Clean Slate inspired by vintage tube amps.

Thinking outside the traditional single box PC, [Jeffrey] built his computer into a series of component-specific boxes all attached to a platform housing the Micro ATX motherboard. The base is made of plywood with a birds-eye maple veneer and each of the component boxes features two different sizes of wire mesh to manipulate the viewer’s perception of the dimensions. Even the I/O and graphics card plates are custom made from aluminum for this build.

If you really want to dig into how this PC came to life, there’s a very detailed build log including every step of the process from bare board to finished product. We love when we get an inside look at the thought process behind each design decision in a build.

We’ve featured [Jeffrey] before with his Humidor Cluster, and you may also like this PC inside a vintage radio.

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An Open Source PowerPC Notebook Edges Closer

Back in 2020, we reported on the effort to create a brand new open-source laptop platform using the PowerPC architecture. At the time they had big plans and a PCB design, and we’re very pleased to report that in the intervening two years they’ve progressed to the point of now having some real prototypes ready for testing.

Some might question why this should be necessary, after all there are plenty of laptops and more than one commonly available processor platform. But that’s to miss the point of open source hardware, that it’s as much about plurality as functionality. But if you’ve only encountered the PowerPC architecture in slightly older Macs and some game consoles, what’s the chip powering this device? The answer is, not one of those venerable chips, but the NXP T2080, a 1.8 GHz quad-core device that boasts a respectable power for a laptop.

There is of course many a hurdle still to be crossed between prototype and final device, but given the challenge of a functioning laptop it’s impressive for them to have reached this milestone at all. We look forward to seeing further iterations, and maybe, just maybe, a finished device one day. Our original coverage is here.

The 10 Kinds Of Programmers That Use Calcutron-33

It is interesting how, if you observe long enough, things tend to be cyclical. Back in the old days, some computers didn’t use binary, they used decimal. This was especially true of made up educational computers like TUTAC or CARDIAC, but there was real decimal hardware out there, too. Then everyone decided that binary made much more sense and now it’s very hard to find a computer that doesn’t use it.

But [Erik] has written a simulator, assembler, and debugger for Calcutron-33, a “decimal RISC” CPU. Why? The idea is to provide a teaching platform to explain assembly language concepts to people who might stumble on binary numbers. Once they understand Calcutron, they can move on to more conventional CPUs with some measure of confidence.

To that end, there are several articles covering the basic architecture, the instruction set, and how to write assembly for the machine. The CPU has much in common with modern microprocessors other than the use of decimal throughout.

There have been several versions of the virtual machine with various improvements and bug fixes. We’ll be honest: we admire the work and its scope. However, if you already know about binary, this might not be your best bet. What’s more is, maybe you should understand binary before tackling assembly language programming, at least in modern times. Still, it does cover a lot of ground that applies regardless.

Made-up computers like TUTAC and CARDIAC were all the rage when computer time was too expensive to waste on mere students. There was also MIX from computer legend Donald Knuth.

Hackerboards: Making Finding The Right Single-Board Computer Easy

The great thing about the wide availability of single-board computers (SBCs) is that it offers such a large selection of options, in terms of CPU performance, GPU features, RAM size, I/O options and much more. This is however also the largest issue, especially with the annual surge of new boards with new feature sets. Trying to make sense of all these offerings is the recently overhauled Board-DB, also known as Hackerboards.

As [Martijn Braam] explains in the blog post on the changes, a major upgrade over the old Hackerboards (which we covered in 2016) is a far more extensive set of parameters that can be filtered against. This makes a fine-grained selection of detailed features significantly easier, which is also reflected in the technical specifications comparison feature. With over 450 active entries there are a lot of boards that can already be filtered on, but manufacturers are invited to take up contact to add further entries, which should keep the list up to date.

Incidentally, if you’d like to know how [Martijn] gets those gorgeous PCB photographs, he wrote a whole a separate write-up that goes over his camera setup.

Thanks to [Vlad] for the tip.

A grey keyboard with orange and dark grey accents is angled away from the camera. The keys nearby are clearly distinguishable in the foreground but blurry toward the back/right. The keyboard is quite thick as it also contains a computer motherboard.

Mechanical Keyboard With A Framework Inside

Like the Commodore 64 and other keyboard computers of yore, the [Elevated Systems]’s CJ64 fits all of its processing and I/O into a single keyboard-shaped package.

This iteration of the project takes it to the next level with an enclosure milled out of aluminum instead of the mere 3D printed enclosure of the previous versions. With a Framework mainboard, the ports are configurable via the Framework expansion card system giving you even more options to customize this build. To round it out, this keyboard PC doesn’t scrimp on the keyboard part either with mechanical switches and MT3 profile keycaps.

If you’d like to build one of these for yourself, [Elevated Systems] has uploaded the 3D printed enclosure files to his GitHub repository. The files for machining are available as well, but only to patrons.

For some more Framework-based mods, check out this Framework Tablet, the Framedeck, or this other retro-inspired Framework build. If you want an all-in-keyboard slabtop, then maybe check out Are Slabtops the Future of Computing?

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The bottom half of a MacBook Air on a purple and pink background has severed wires drawn out of its back to indicate its lack of a screen.

Are Slabtops The Future Of Computing?

The most popular computer ever was the Commodore 64 with its computer-in-a-keyboard form factor. If you have a longing for a keyboard computer with more modern internals, one of the easiest solutions today is to pull the screen off a laptop.

[Umar Shakir] wanted to see what the fuss was about regarding a recent Apple patent and took the top lid off of his M1 Macbook Air and turned it into a “slabtop.” The computer works great wired to a monitor but can also be used wirelessly via AirPlay. The approach doesn’t come without its downsides, of course. Newer MacBooks can’t access recovery mode without the built-in screen, and some older models had their WiFi antennas in the top lid, so making one into a slabtop will leave you desk-bound.

While [Shakir] focuses on MacBooks, this approach should work with any laptop. Apparently, it’s a cottage industry in China already. Back in the day, my own daily driver was a Pentium-powered laptop with its broken LCD (and lid) removed. It worked great with whatever CRT was nearby.

If you’re looking for an off-the-shelf keyboard computer of your own, you might want to check out the Raspberry Pi 400.