Turning Old Cellphones Into SBCs

April 8, 2025 by Elliot Williams 35 Comments

[David] sent us a tip about a company in Belgium, Citronics, that is looking to turn old cellphones into single-board computers for embedded Linux applications. We think it’s a great idea, and have long lamented how many pocket supercomputers simply get tossed in the recycling stream, when they could be put to use in hacker projects. So far, it looks like Citronics only has a prototyping breakout board for the Fairphone 2, but it’s a promising idea.

One of the things that’s stopping us from re-using old phones, of course, is the lack of easy access to the peripherals. On the average phone, you’ve got one USB port and that’s it. The Citronics dev kit provides all sorts of connectivity: 4x USB 2.0, 1x Ethernet 10/100M, and a Raspberry Pi Header (UART, SPI, I2C, GPIO). At the same time, for better or worse, they’ve done away with the screen and its touch interface, and the camera too, but they seem to be keeping all of the RF capabilities.

The whole thing runs Linux, which means that this won’t work with every phone out there, but projects like PostmarketOS and others will certainly broaden the range of usable devices. And stripping off the camera and screen has the secondary advantages of removing the parts that get most easily broken and have the least support from custom Linux distros.

We wish we had more details about the specifics of the break-out boards, but we like the idea. How long before we see an open-source implementation of something similar? There are so many cheap used and broken cellphones out there that it’s certainly a worthwhile project!

A Closer Look At The Tanmatsu

February 4, 2025 by Jenny List 27 Comments

A few weeks ago we brought you news of a new palmtop computer for hackers, powered by the new Espressif ESP32-P4 application processor. The Tanmatsu (Japanese for “Terminal”) is a compact handheld device with a QWERTY keyboard and an 800×480 DSI display, and while it currently exists at the final prototype stage there is a pre-order page upon which you can reserve an early production model for yourself. We’ve been lucky enough to be invited to give one a close-up inspection, so it was time to hot-foot it on the train to a Dutch hackerspace in order to bring you a preview.

A Little History, And First Impressions

The Tanmatsu, held in both hands. — Recesses in the case fit well against the hands.

Before looking at the device, it’s time for a little history. The Tanmatsu has its origin in badge.team, the Netherlands-based group that has produced so many European event badges over the years, and it was destined to eventually become the badge for the upcoming WHY2025 hacker camp. As sometimes happens in any community there has been a significant difference of opinion between the event orga and the badge.team folks that it’s inappropriate to go into here, so now it exists as a standalone project. It’s destined to be open-source in its entirety including hardware and software (and we will hold them to that, never fear), but because of the events surrounding its conception the full repositories will be not be made public until some time late in the summer.

Picking the Tanmatsu up and holding it, it’s a rectangular slab a bit larger and thicker than a CD case with that QWERTY keyboard and display on its front face, an array of ports including an SMA socket for a LoRA antenna on its sides, and an expansion connector on its rear. It has a sandwich construction, with a PCB front face, a 3D printed spacer, the PCB itself, and a 3D printed back cover all held together with a set of screws. The recesses on its bottom edge and the lower halves of the sides locate neatly with fingers and thumbs when it’s held in two hands for two-thumb typing. The keyboard is a silicone moulding as is common on this type of device, and while the keys are quite small it was not difficult to type on it. The display meanwhile feels of much higher quality than the SPI parts previously seen on badges. Continue reading “A Closer Look At The Tanmatsu” →

Go Forth With This Portable Programmer

June 29, 2024 by Bryan Cockfield 14 Comments

When choosing a low-level language, it’s hard to beat the efficiency of Forth while also maintaining some amount of readability. There are open source options for the language which makes it accessible, and it maintains its prevalence in astronomical and other embedded systems for its direct hardware control and streamlined use of limited resources even though the language started over 50 years ago. Unlike 50 years ago, though, you can now take your own self-contained Forth programmer on the go with you.

The small computer is built on a design that [Dennis] built a while back called my4TH which has its own dedicated 8-bit CPU and can store data in a 256 kB EEPROM chip. Everything else needed for the computer is built in as well but that original design didn’t include a few features that this one adds, most notably a small 40×4 character LCD and a keyboard. The build also adds a case to tie everything together, with ports on the back for I2C and power plus an RS232 port. An optional battery circuit lets the computer power up without an external power supply as well.

Continue reading “Go Forth With This Portable Programmer” →

The World’s First DIY Minicomputer Was Almost Australian

June 12, 2024 by Elliot Williams 23 Comments

The EDUC-8, a DIY minicomputer design that came out in “Electronics Australia” magazine, was almost the world’s first in August 1974. And it would have been tied for the world’s first if inventor [Jamieson “Jim” Rowe] hadn’t held back from publishing to rework the design to expand the memory to a full 256 bytes. The price of perfectionism?

Flash forward 50 years, and [Gwyllym Suter] has taken on the job of recreating the EDUC-8 using modern PCBs, but otherwise staying true to the all-TTL design. He has all of his schematics up on the project’s GitHub, but has also sent us a number of beauty shots that we’re including below. Other than the progress of PCB tech and the very nice 3D-printed housing, they look identical. We have to admit that we love those wavy hand-drawn traces on the original, but we wouldn’t be sad about not having to solder in all those jumpers.

Continue reading “The World’s First DIY Minicomputer Was Almost Australian” →

Inside A Mystery Aerospace Computer With [Ken Shirriff]

June 1, 2024 by Dan Maloney 10 Comments

When life hands you a mysterious bit of vintage avionics, your best bet to identifying it might just be to get it in front of the biggest bunch of hardware hounds on the planet. After doing a teardown and some of your own investigation first, of course.

The literal black box in question came into [Ken Shirriff]’s custody courtesy of [David] from Usagi Electric, better known for his vacuum tube computer builds and his loving restoration of a Centurion minicomputer. The unit bears little in the way of identifying markings, but [Ken] was able to glean a little by inspecting the exterior. The keypad is a big giveaway; its chunky buttons seem optimized for use with the gloved hands of a pressure suit, and the ordinal compass points hint at a navigational function. The layout of the keypad is similar to the Apollo DSKY, which might make it a NASA artifact. Possibly contradicting all of that is the oddball but very cool electromechanical display, which uses reels of digits and a stepper-like motor to drive them.

Inside, more mysteries — and more clues — await. Unlike a recent flight computer [Ken] looked at, most of the guts are strictly electronic. The instrument is absolutely stuffed with PCBs, most of which are four-layer boards. Date codes on the hundreds of chips all seem to be in the 1967 range, dating the unit to the late 60s or early 70s. The weirdest bit is the core memory buried deep inside the stacks of logic and analog boards. [Ken] found 20 planes with the core, hinting at a 20-bit processor.

In the end, [Ken] was unable to come to any firm conclusion as to what this thing is, who made it, or what its purpose was. We doubt that his analysis will end there, though, and we look forward to the reverse engineering effort on this piece of retro magic.

Homebrew Computer From The Ground Up

May 26, 2024 by Bryan Cockfield 12 Comments

Building a retro computer of some sort is a rite of passage for many of us, with some building replicas or restorations of old Commodores, Ataris, and other machines from decades past. Others go even further back, to the time of the Intel 8008 or earlier, and a dedicated few will build something completely novel. This project from [3DSage] falls squarely in the latter category, with his completely DIY computer built component by component from scratch, including the machine code needed to run it.

[3DSage] starts with the backbone of every computer: the clock. He first demonstrates how a pair of NOT gates with a set of capacitors can be used as a rudimentary clock pulse, then builds a more refined version with a 555 timer and potentiometer for adjustable rates. Then, it’s on to creating a binary counter, which is a fundamental part of the memory system for this small computer, and finally, allows this circuitry to behave like a normal computer. Using a set of switches to store values in memory and stepping through them with the clock, the computer can be programmed to do plenty of tasks just like a modern microcontroller.

[3DSage] built this project a few years ago and has used it for real-world applications such as controlling servos, LED arrays, playing music, and other tasks. Although he has to program it using his own machine code by hand, it’s a usable computer in many ways. If you want to eschew modernity and build a retro computer in the style of the 1960s, though, this piece goes through what it would have been like to build a similar system in the era when these computers were more common. If you have a switch fetish, you might like to see how real computers worked back then, too.

Continue reading “Homebrew Computer From The Ground Up” →

Keep Tabs On PC Use With Custom Analog Voltmeter

April 26, 2024 by Bryan Cockfield 8 Comments

With the demands of modern computing, from video editing, streaming, and gaming, many of us will turn to a monitoring system of some point to keep tabs on CPU usage, temperatures, memory, and other physical states of our machines. Most are going to simply display on the screen but this data can be sent to external CPU monitors as well. This retro-styled monitor built on analog voltmeters does a great job of this and adds some flair to a modern workstation as well.

The build, known as bbMonitor, is based on the ESP32 platform which controls an array of voltmeters via PWM. The voltmeters have been modified with a percentage display to show things like CPU use percentage. Software running on the computers sends this data in real time to the ESP32 so the computer’s behavior can be viewed at a glance. Each voltmeter is also augmented with RGB LEDs that change color from green to red as use increases as well. The project’s creator, [Corebb], also notes that the gauges will bounce around if the computer is under heavy load but act more linearly when under constant load, also helping to keep an eye on computer status.

While the build does seem to rely on a Windows machine to run the software for export to the monitor, all of the code is open-sourced and available on the project’s GitHub page and could potentially be adapted for other operating systems. And, as far as the voltmeters themselves go, there have been similar projects in the past that use stepper motors as a CPU usage monitor instead.

Continue reading “Keep Tabs On PC Use With Custom Analog Voltmeter” →