Front and back of a handheld 6502 computer with bubble LED displays

The Pocket265 Is A Pocket-Sized 6502 Single-Board Computer

September 7, 2022 by Robin Kearey 13 Comments

Single-board computers have been around ever since microprocessors became affordable in the 1970s and never went away. Today we have Raspberry Pis and LattePandas, while back in the ’70s and ’80s there were the Ferguson Big Board, the KIM-1 and a whole array of Intel SDK boards. Although functionally similar to their modern counterparts with a CPU, RAM, ROM and some basic peripherals, the old boards were huge compared to today’s tiny platforms and typically required a rather beefy power supply to operate.

It doesn’t have to be that way though, as [Aleksander] shows with the Pocket265: a handheld 6502 single-board computer somewhat reminiscent of the famous KIM-1. Like that classic machine, it’s got a hexadecimal keypad to enter programs using machine code and a row of LED displays to show the programs’ output. Unlike the KIM, the Pocket265 is small enough to hold in one hand and uses bubble LED displays, which make it look more like a programmable calculator from the 1970s. It comes with a lithium battery that makes it truly portable, as well as a sleek 3D printed case to make it more comfortable to hold than a bare circuit board.

The single ROM chip contains a monitor program that runs the basic user interface. It also makes programming a bit less tedious by implementing a number of system calls to handle things like user input and display output. A serial EEPROM enables local data storage, while a UART with a USB interface enables data transfer to other computers. If you’re interested in building and programming such a machine yourself, [Aleksander] helpfully provides code examples as well as full hardware documentation on his GitHub page.

The 6502 remains a firm favorite among hardware hackers: some projects we recently featured with this CPU include one beautifully made machine, this easy-to-build single-board computer and this huge breadboard-based contraption. Looking for something smaller? Try this tidy little board or this 6502 coupled to an FPGA.

KittyOS: Writing A Toy OS For The ATmega168 From Scratch

September 5, 2022 by Dave Rowntree 6 Comments

Writing an operating system for a computing platform is one of those non-trivial tasks few people actually need to do, regardless of whether it’s for a small microcontroller or a larger general-purpose computer. Many of us spend a large amount of our time working on producing robust code for embedded systems, occasionally diving deeper into the abstraction when we’re stuck on a problem. Quite often this work is sitting on top of an RTOS, which we consider a solved problem. [Jonathan Diamond] had picked up a fair bit of knowledge of some of the low-level AVR black magic, as well as some details of how operating systems work internally, and so decided to have a crack a building a toy operating system called KittyOS, for the learning experience alone.

[Jonathan] hastens to add that this is not a practical OS, but a learning platform that needs a few more bells and whistles added to be useful. Aimed at the 8-bit AVR ATmega168 with its mere 16kB of flash and 1kB of SRAM, the diminutive chip can still perform more than well enough to host the rudimentary OS — up to four application tasks, and some basic system call support.

Already, KittyOS sports preemptive multitasking, with prioritization and support for applications written in C. Hardware support is a bit limited, with just serial I/O and a spot of GPIO, but that’s more than enough for a demonstrator. Applications can be loaded into any of the four available slots, with per-slot run state control, using the Python-based host interface. The post is a long one, with an absolute ton of the gory details we love around these parts, and we’re very glad [Jonathan] took the time to make a proper write-up as well as a demonstration video, which can be found after the break.

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An Amstrad Portable You Won’t Have Seen

August 30, 2022 by Jenny List 6 Comments

Of all the players in the home computer world in the 1980s, Alan Sugar’s Amstrad was a step ahead in ease of use over its competitors. The Amstrad CPC series of computers came with their own monitors that also had a built-in power supply, and featured built-in data recorders or disk drives as standard. Despite having a line of business computers and an eventual move into PC territory that included portable machines, Amstrad never produced a CPC which wasn’t anchored to the desktop. [Michael Wessel] has taken that challenge on himself with a CPC464 that had a broken cassette recorder, and come up with a creditable take on a portable computer that never was.

Starting with an ethos of not modifying the CPC case more than necessary, the defective tape drive has gone to be replaced with an HDMI TFT screen and a video converter board. In went a 512K RAM expansion, an SD card disk expansion, and a stereo amplifier. A small power supply board also takes power for the unit via USB-C, such that it can operate from a power bank.

The result is a fully functional and hugely expanded CPC that’s as much cyberdeck as it is retrocomputer, and given that if we remember correctly that these machines were CP/M capable it could be of greater use than simply gaming. [Michael] hasn’t entered his creation into our ongoing Cyberdeck Contest, but we think it would make a strong contender.

This isn’t the first Amstrac CPC we’ve shown you, here’s a very different take on a modernized machine.

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C64 Turned Theremin With A Handful Of Parts

August 30, 2022 by Zoe Skyforest 7 Comments

The theremin is popular for its eerie sound output and its non-contact playing style. While they’re typically built using analog hardware, [Linus Åkesson] decided to make one using the venerable Commodore 64.

The instrument works by measuring the capacitance between its two antennas and the Earth. As these capacitances are changed by a human waving their hands around near the respective pitch and volume antennas, the theremin responds by changing the pitch and volume of its output.

In this case, the humble 555 is pressed into service. It runs as an oscillator, with its frequency varying depending on the user’s hand position. There’s one each for pitch and volume, naturally, using a clamp and spoon as antennas. The C64 then reads the frequency the 555s are oscillating at, and then converts these into pitch and volume data to be fed to the SID audio chip.

[Linus Åkesson] demonstrates the build ably by performing a slow rendition of Amazing Grace. The SID synthesizer chip in the C64 does a passable job emulating a theremin, used here with a modulated pulse wave sound. It’s an impressive build and one we fully expect to see at a big chiptune show sooner rather than later. We’re almost surprised nobody came out with a C64 Theremin cartridge back in the day.

We’ve seen other fancy theremin-inspired builds recently too, like this light-based design.

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YouTube Like It’s 1970s France With This Minitel-VCR Mashup

August 27, 2022 by Dan Maloney 10 Comments

When it’s not just sticking fake gears on things and calling it a day, the Steampunk look is pretty cool. Imagining technology in a world stuck with Victorian aesthetics is a neat idea, and one that translates to the look of other time periods — Fallout, anyone?

But what if you try to create a technological aesthetic based on a more recent and less celebrated time? That’s what [ghettobastler] has attempted with this somewhat bizarre Minitel-YouTube-VCR mash-up. Taking inspiration from a webcomic’s take on “Formicapunk,” modern tech based on the aesthetic of the wildly successful French videotex service of the 70s and 80s, the system uses a very cool Minitel 1B terminal and a Raspberry Pi 3.

With the help of a level-shifting circuit, the Mintel and the Pi talk over serial, allowing the terminal to be used as, well, a terminal for the Pi. Videos are downloaded from YouTube by the Pi, which sends the video to the VCR from its composite output, and controls the VCR with an IR LED that emulates the original remote. Come to think of it, just watch the video below — it’s probably easier than trying to describe it.

It’s weird, true, but we love the look of that Minitel terminal. Something about it just screams cyberdeck; if anyone has a spare one of these, get busy and put something together for our Cyberdeck Design Contest.

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IBM’s Early PC Attracts Time Travelers

August 23, 2022 by Al Williams 53 Comments

It wasn’t long ago I was nostalgic about an old computer I saw back in the 1980s from HP. It was sort of an early attempt at a PC, although price-wise it was only in reach for professionals. HP wasn’t the only one to try such a thing, and one of the more famous attempts was the company that arguably did get the PC world rolling: IBM. Sure, there were other companies that made PCs before the IBM PC, but that was the computer that cemented the idea of a computer on an office desk or at your home more than any computer before it. Even now, our giant supercomputer desktop machines boot as though they were a vintage 1981 PC for a few minutes on each startup. But the PC wasn’t the first personal machine from IBM and, in fact, the IBM 5100 was not only personal, but it was also portable. Well, portable by 1970s standards that also had very heavy video cameras and luggable computers like the Osborne 1.

The IBM 5100 had a brief three-year life from 1975 to 1978. A blistering 1.9 MHz 16-bit CPU drove a 5-inch CRT monitor and you could have between 16K and 64K of RAM along with a fair amount of ROM. In fact, the ROMs were the key feature and a giant switch on the front let you pick between an APL ROM and a BASIC ROM (assuming you had bought both).

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An ASCII Terminal Like It’s 1974

August 21, 2022 by Jenny List 10 Comments

It’s quite probable that any of you who have built a keyboard will have done so using a matrix of keys connected to a microcontroller, or if you are old-school, a microprocessor. A CPU can scan the keyboard matrix with ease, and pass whatever is typed either to whatever software it is running, or to a host computer. There was a time however when available CPUs were not considered powerful enough to do all this and also perform a useful task, so a keyboard would have its own decoder chip that would output ASCII over a parallel interface. It’s an era [John Calhoun] harks back to with Adam74, a little ASCII terminal which takes its input from that 7-bit parallel port.

In the place of a forest of TTL chips which might have graced the originals, within that attractive curved laser cut acrylic case is an LCD display and a Teensy microcontroller board. There’s a level shifter for the classic 5 volt logic, and of course a small buzzer for the essential BEL character. In these days when a parallel interface is relatively rare, he describes the rediscovery of alternate earth lines in a ribbon cable to minimize cross-talk. Should you wish to try your own, everything can be found on GitHub.

All in all it’s a fun way to rediscover an old idea.