DIY 8-Bit Computer Knows All The Tricks

Some projects are a rite of passage within their respected fields. For computer science, building one’s own computer from scratch is certainly among those projects. Of course, we’re not talking about buying components online and snapping together a modern x86 machine. We mean building something closer to a fully-programmable 8-bit computer from the ground up, like this one from [Federico] based on 74LS logic chips.

The computer was designed and built from scratch which is impressive enough, but [Federico] completed this project in about a month as well. It can be programmed manually through DIP switches or via a USB connection to another computer, and also includes an adjustable clock which can perform steps anywhere from 1 Hz to 32 kHz. Complete with a 1024 byte memory, a capable ALU, four seven-segment LEDs and (in the second version of the computer) a 2×16 LCD disply, this 8-bit computer has it all.

Not only is this a capable machine designed by someone who clearly knows his way around a logic chip, but [Federico] has also made the code and schematics available on his GitHub page. It’s worth a read even without building your own, but if you want to go that route without printing an enormous PCB you can always follow the breadboard route.

Thanks to [killergeek] for the tip!

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A Novel Micro Desktop Display For Your Raspberry Pi

Since its debut back in 2012 there have been a variety of inventive displays used with the Raspberry Pi. Perhaps you remember the repurposed Motorola phone docks, or you have one of those little displays that plugs into the expansion port. Inevitably the smaller options become disappointing as desktop displays, because while the advert triumphantly shows them sporting a Raspberry Pi OS desktop the reality is almost unusable. Until now.

Along comes [igbit] with a solution in the form of a little SPI display with a different approach to displaying a desktop. Instead of displaying a matchbox-sized desktop over the whole screen it divides into two halves. At the top is a representation of the desktop, while below it is a close-up on the area around the mouse pointer.

Unexpectedly its mode of operation is very accessible to the non-Linux guru, because it works through a Python script that takes screenshots of both areas and passes them as a composite to the display. An area the size of the magnified window is drawn around the mouse pointer, allowing it to be easily located on the tiny desktop. It relies on the main display being pushed to the HDMI output, so if the Pi is otherwise headless then its configuration has to be such that it forces HDMI use. The result isn’t something that would help you with the more demanding desktop tasks, but it provides a neat solution to being able to use a Pi desktop on a tiny screen.

Of course, in a pinch you can always use your mobile phone.

Squeezing Every Bit From An ATMega

While the ATMega328 is “mega” for a microcontroller, it’s still a fairly limited platform. It has plenty of I/O and working memory for most tasks, but this Battleship game that [thorlancaster328] has put together really stretches the capabilities of this tiny chip. Normally a Battleship game wouldn’t be that complicated, but this one has audio, an LED display, and can also play a fine rendition of Nyan Cat to boot, which really puts the Atmel chip through its paces.

The audio is played through a 512-byte buffer and an interrupt triggers the microcontroller when to fill the buffer while it works on the other processes. The 12×12 LED display is also fed through a shift register triggered by the same interrupt as the audio, and since the build uses so many shift registers the microcontroller can actually output four separate displays (two players, each with a dispaly for shots and one for ships). It will also eventually support a player-vs-computer mode for the battleship game, and also has a mode where it plays Nyan cat just to demonstrate its own capabilities.

We’re pretty impressed with the amount of work this small microcontroller is doing, largely thanks to code optimization from its creator [thorlancaster328]. If there’s enough interest he also says he will provide the source code too. Until then, be sure to check out this other way of pushing a small microcontroller to its limits.

Thanks to [Thinkerer] for the tip!

Templateize Your Timetable With EPaper Templates

To date, e-paper technology has been great for two things, displaying static black and white text and luring hackers with the promise of a display that is easy on the eyes and runs forever. But poor availability of bare panels has made the second (we would say more important) goal slow to materialize. One of the first projects that comes to mind is using such a display to show ambient information like a daily summary weather, train schedules, and calendar appointments. Usually this means rolling your own software stack, but [Christopher Mullins] has put together a shockingly complete toolset for designing and updating such parameterized displays called epaper_templates.

To get it out of the way first, there is no hardware component to epaper_templates. It presupposes you have an ESP32 and a display chosen from a certain list of supported models. A quick search on our favorite import site turned up a wide variety of options for bare panels and prebuilt devices (ESP32 and display, plus other goodies) starting at around $40 USD, so this should be a low threshold to cross.

Once you have the device, epaper_templates provides the magic. [Christopher]’s key insight is that an ambient display is typically composed of groups of semi-static data displayed in a layout that never changes. The only variation is updates to the data which is fully parameterized: temperature is always integer Fahrenheit, train schedules are lists of minutes and hours, etc. Layouts like this aren’t difficult to make, but require the developer to reimplement lots of boilerplate. To make them easy to generate, epaper_templates provides a fully featured web UI to let the user freely customize a layout, then exports it as JSON which the device consumes.

The sample layout configured in the video below

The web UI is shockingly capable, especially for by the standards of the embedded web. (Remember it’s hosted on the ESP32 itself!) The user can place text and configure fonts and styles. Once placed, the text can be set to static strings or tied to variables, and if the string is a timestamp it can be formatted with a standard strftime format string.

To round out the feature set, the user can place images and lines to divide the display. Once the display is described, everything becomes simple to programmatically update. The ESP can be configured to subscribe to certain MQTT topics from which it will receive updates, or if that is too much infrastructure there is a handy REST API which accepts JSON objects containing variables or bitmaps to update on device.

We’re totally blown away by the level of functionality in epaper_templates! Check out the repo for more detail about its capabilities. For a full demo which walks through configuration of a UI with train arrival times, weather, both instant temperature and forecast with icons, and date/time check out the video after the break. Source for the example is here, but be sure to check out examples/ in the repo for more examples.

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An IMac All-In-One’s New Life

There’s a sleek form factor for desktop computers known as an “all-in-one” that enrobes a computer in a monitor. While the convenience of having all your computing in a neat package has some nice benefits, it comes with an unfortunate downside. Someday the computer inside is going to be old and outdated in comparison to newer machines. While a new OS goes a long way towards breathing life into an old machine, [Thomas] has decided to take the path less travelled and converted an old iMac all-in-one into a discrete monitor.

The iMac in question is the 20″ iMac G5 iSight (A1145) with an LG-Philips LM201W01-STB2 LCD panel. Looking back, [Thomas] would recommend just ordering an LCD driver controller kit from your favourite auction house. But for this particular modification, he decided to do things a little bit more manually and we’re quite glad he did.

Luckily for [Thomas], the panel supports TMDS (which both DVI and HDMI are compatible with). So the next step was to figure out the signalling wires and proper voltages. After some trouble caused by a mislabeled power line on the iMac PCB silk-screen (12v instead of 3.3v), he had all the wires identified and a plan starting to form. The first step was a circuit to trick the inverter into turning on with the help of a relay. The female HDMI plug with a breakout board was added and sticks out through the old firewire port. The minuscule wires in the display ribbon cable to the monitor were separated and soldered onto with the help of [Thomas’] daughter’s microscope. Resistances were checked as HDMI relies on impedance matched pairs. To finish it off, an old tactile toggle switch offers a way to turn the monitor on and off with a solid thunk.

We love seeing old hardware being repurposed for new things. This project nicely complements the iMac G4 Reborn With Intel NUC Transplant we saw earlier this year, as they both try to preserve the form factor while allowing a new computer to drive the display.

Computer Vision Maps Christmas Lights

There’s a small but dedicated group of folks out there who spend all year planning their Christmas decorations. These aren’t simple lawn ornaments or displays, either, but have evolved into complex lightning performances that require quite a bit of computer control. For some things, hooking up a relay to a microcontroller can get the job done, but [Andy] has turned to computer vision to solve some of the more time-consuming aspects of these displays.

Specifically, [Andy] has a long string of programmable RGB LED lights to wrap around a Christmas tree, but didn’t want to spend time manually mapping out each light’s location. So he used OpenCV to register the locations of the LEDs from three different camera angles, and then used a Python script to calculate their position in the 3D space. This means that he will easily be able to take the LEDs down at the end of the holidays and string them back up next year without having to do the tedious manual mapping ever again.

While [Andy] notes that he may have spent more time writing the software to map out the LEDs than manually doing it himself, but year-after-year it may save him a lot of time and effort, not to mention the benefits of a challenge like writing this software in the first place. If you want to get started on your own display this year, all you really need is some lights and a MIDI controller.

The Art Of Nixies Hack Chat

Join us on Wednesday, October 28th at noon Pacific for The Art of Nixies Hack Chat with Dalibor Farný!

When they were invented in the 1950s, Nixie tubes were a huge leap forward in display technology. In the days before affordable LEDs made seven-segment displays a commodity, there were few alternatives to the charming glow of the clear and legible characters inside Nixies. Sturdy and reliable, the cold-cathode displays found their way into everything from scientific instruments to test equipment, and even some of the earliest computers and the equipment that formed the foundation of the Space Race sported the venerable tubes.

But time marches on, and a display that requires high voltage and special driver circuits isn’t long for a world where LEDs are cheap and easy to design with. Nixies fell from favor through the late 1960s and 1970s, to the point where new tubes were only being made by the Russians, until that supply dried up as well. Rediscovered by hobbyists for use in quirky clocks and other displays, any stock left over from the Nixie’s heyday are quickly being snapped up, putting the tubes on the fast track to unobtainium status.

That’s not to say that you can’t get brand new Nixie tubes, of course. Artisanal manufacturers like Dalibor Farný have taken the Nixie to a whole new level, with big, beautiful tubes that are handcrafted from the best materials. Reviving the somewhat lost art of Nixie manufacturing wasn’t easy, but the tubes that Dalibor makes in a castle in the Czech Republic now find their way into cool clocks and other builds around the world. He’ll join us on the Hack Chat to dive into the art and science of Nixies, and what’s going on with his mysterious “Project H”.

join-hack-chatOur Hack Chats are live community events in the Hack Chat group messaging. This week we’ll be sitting down on Wednesday, October 28 at 12:00 PM Pacific time. If time zones baffle you as much as us, we have a handy time zone converter.

Click that speech bubble to the right, and you’ll be taken directly to the Hack Chat group on You don’t have to wait until Wednesday; join whenever you want and you can see what the community is talking about.

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