Pi Pico-Powered ATX Motherboard

June 22, 2021 by Chris Lott 18 Comments

For a couple of years, embedded developer and Rust addict [Jonathan Pallant] aka [theJPster] has been working on a simple computer which he calls the Neotron. The idea is to make a computer that is not only easy to use but easy to understand as well. He describes it as a CP/M- or DOS-like operating system for small ARM microcontrollers. His most recent project is powered by a Raspberry Pi RP2040 Pico and built in the format of a microATX motherboard. This board packs a lot of features for a Pico-based design, including 12-bit color VGA and seven expansion slots. See his GitHub repository for a full list of specifications, and all the files needed to build your own — it is an Open Source project after all.

Besides the Neotron Pico itself, a couple of gems caught our eye in this well-documented project. [theJPster] was running out of I/O pins on the Pico, and didn’t have enough left over for all the peripherals’ chip selects. Check out how he uses an MCP23S17 SPI-bus I/O expander and a tri-state buffer to solve the problem.

On a more meta level, we are intrigued by his use of GitHub Actions. Per the standard concept of repositories, they shouldn’t contain the results of a build, be that an executable binary or Gerber files. Distribution of the build products is typically handled outside of GitHub, using something like GitHub’s Large File Storage service, or just ignoring convention altogether and putting them in the repo anyway. [theJPster] uses another method, employing GitHub Actions to generate the files needed for PCB fabrication, for example.

The Neotron Pico is the latest in a series of boards made to run Neotron OS. Previous boards include:

Neotron 9x — Microchip SAM9X
Neotron 1000 — STM32H7 + Lattice Semi iCE40 FPGA
Neotron 600 — Teensy 4.1
Neotron 340ST — ST 32F746G-DISCOVERY

See Acorn Archimedes Get Repaired And Refurbished, In Glorious Detail

June 21, 2021 by Donald Papp 3 Comments

Want to see a 90s-era Acorn Archimedes A3020 home computer get opened up, refurbished, and taken for a test drive? Don’t miss [drygol]’s great writeup on Retrohax, because it’s got all that, and more!

A modern upgrade allowing the use of a CF card in place of an internal hard drive, via a CF2IDE adapter and 3D-printed fixture.

The Archimedes was a line of ARM-based personal computers by Acorn Computers, released in the late 80s and discontinued in the 90s as Macintosh and IBM PC-compatible machines ultimately dominated. They were capable machines for their time, and [drygol] refurbished an original back into working order while installing a few upgrades at the same time.

The first order of business was to open the machine up and inspect the internals. Visible corrosion gets cleaned up with oxalic acid, old electrolytic capacitors are replaced as a matter of course, and any corroded traces get careful repair. Removing corrosion from sockets requires desoldering the part for cleaning then re-soldering, so this whole process can be a lot of work. Fortunately, vintage hardware was often designed with hand-assembly in mind, so parts tend to be accessible for servicing with decent visibility in the process. The keyboard was entirely disassembled and de-yellowed, yielding an eye-poppingly attractive result.

Once the computer itself was working properly, it was time for a few modern upgrades. One was to give the machine an adapter to use a CF card in place of an internal IDE hard drive, and [drygol] did a great job of using a 3D-printed piece to make the CF2IDE adapter look like a factory offering. The internal floppy drive was also replaced with a GOTEK floppy emulator (also with a 3D-printed adapter) for another modern upgrade.

The fully refurbished and upgraded machine looks slick, so watch the Acorn Archimedes A3020 show off what it can do in the video (embedded below), and maybe feel a bit of nostalgia.

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Raspberry Pi Floppy Driver Uncovers Fishy Secrets

June 21, 2021 by Chris Lott 13 Comments

A forum post by New Zealand electronics enthusiast [zl2wrw] about retreiving waypoints from a mysterious floppy disk caught our eye. The navigation system on his friend’s fishing boat had died and was replaced. But the old waypoints were stored on a 3-1/2 inch floppy disk that was unreadable on a normal PC. Not to be deterred, [zl2wrw] then looked for another solution — apparently a list of hot NZ fishing spots is worth quite the effort.

The tool he discovered, and the main point of this story, is the bbc-fdc by [Jasper Renow-Clarke] aka [picosonic]. [Jasper] made this project to read 5-1/4 inch Acorn DFS floppies from his BBC Micro. But bbc-fdc can be used to read a variety of floppy disk formats, such as DOS, C64, Apple II, and others It can also just capture raw magnetic flux transitions on the disk, blissfully unaware of any logical structure to the data. We recently wrote about another Raspberry Pi Floppy Drive Controller project by [Scott Baker]. What sets [picosonic]’s project apart is that he’s not using an FDC controller chip here. The only interface electronics is a couple of open-collector 7406 ICs. Data is read using the SPI peripheral. If you need to archive old floppy disks or do a forensic analysis of unknown disks like [zl2wrw], then one of these two projects will almost certainly do the trick.

Meanwhile back in New Zealand, [zl2wrw] discovered that the floppy format was standard (Modified Frequency Modulation, MFM) by examining the raw flux dump. However, the filesystem was a mystery — it didn’t quite match any of the usual suspects. So [zl2wrw] dug into the hex dump of the data and figured out enough of the structure to manually recover the waypoints. Subsequently, a user on the forum found a document describing the file system used by Furuno GPS units, which proved to be a close match albeit after the fact. Alas, [zl2wrw] hasn’t publish the coordinates of those good fishing spots.

Have you had any successes (or failures) when it comes to reading data from old disks? Or have you encountered peculiar disk formats and/or file systems, where having a tool like this could have been helpful? Let us know in the comments below.

Translate Your CP/M Code To 8086, And Leave The 1970s Behind!

June 13, 2021 by Jenny List 34 Comments

“Bring our home computing out of the 1970s and into the 1980s and beyond” is the irresistible promise made by the creator of 8088ify, a piece of software which translates CP/M executables from their 8080-based originals to assembler code that should run on an 8088 under MS/DOS. How can we resist such a futuristic promise here in 2021, even though the code wasn’t written to the sound of Donna Summer or the Village People back in the day but here in 2021 for PCjam, a celebration of the original IBM PC’s 40th anniversary.

As the writer of this code [ibara] points out that Intel intended the 8088 to be a ready upgrade path for the 8080, and designed its instruction set while not directly compatible, to make translation between the two a straightforward process. There was commercial software for the task at the time, but to this day there remained nothing with an open-source licence. It’s written in ANSI C for portability across platforms and compilers, and can even be compiled under CP/M itself.

PCjam is well worth a look, and if any of you fancy a go at writing for the earliest MS-DOS machines we’d like to suggest you create something for it. Meanwhile if you’d like to explore CP/M, you can run a bare metal emulator on the Raspberry Pi.

Header: Thomas Nguyen, CC BY-SA 4.0.

A Dual Monitor Setup For The C64, And Yes, It’s VGA Compatible

June 10, 2021 by Zoe Skyforest 9 Comments

Few in the 1980s were too fussed about their home computer only supporting a single monitor; indeed, most were satisfied enough by the brand new capabilities on offer at the time. That said, it’s many decades hence, and we really do deserve more. Fear not, for [Ryan Brooks] is here to help with his VG64 VGA Card for the Commodore 64.

The card sits in the cartridge slot of the Commodore 64, and packs a Xilinx CPLD which is responsible for generating the video output signals. It’s hooked up to an SRAM chip which acts as a frame buffer for the video output. Programs can then be loaded on the Commodore 64 which write to the frame buffer, that can then be sent out to an attached VGA monitor hooked up to the cartridge.

It’s not the most useful cart at the moment, as it’s only capable of working with software designed specifically for the hardware. Additionally, it could prove difficult to shift enough data to it to do any kind of fast animation or updates. With that said, it’s an awesome example of just what can be achieved in terms of expanding the Commodore 64, and we’d love to see how far work in this space can go. We’ve seen similar work before, too, albeit with a somewhat smaller 16×2 character LCD. Video after the break.

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Cerberus 2080 — Three-Headed Retro Computing Project

June 8, 2021 by Chris Lott 6 Comments

For seven months, [Bernardo Kastrup] at [TheByteAttic] has been realizing his childhood dream of building his own computer. It was this dream that steered him into the field of computer design at the age of 17. After thirty years in the industry, he finally has some time to design the computer he dreamt about as a kid. His requirements are ambitious: fully open design, gate-level details, thru-hole or PLCC for easy hacking, well-established processors with existing tool chains, low-cost development tools for CPLDs, no FPGA, standard ITX case compatible, and so on. He quite reasonably decides to use more modern electronics for video (VGA), keyboard (PS/2), and program storage (flash drive). Along the way, he chooses to put three processors on the board instead of one:

Zilog Z84C0010 (Z80)
WDC W65C0256 (6502)
AVR ATMEGA328 (RISC Controller)

When coming up with the concept and requirements, [Bernardo] had a fictitious alternate history in mind — one where there were follow-ups to the ZX80, PET/CBM, or TRS-80 from the late 1970s that were extensions to the original systems. But he also wanted a clean design, without cost-cutting gimmicks, in order to make it easier for learners to focus on computing itself — a didactic architecture, as he describes it. Turn the crank for seven long months, and we have the Cerberus 2080. [Bernardo] has put the design on GitHub, and made a video series out of the whole process, of which the introduction video is below the break. There’s even an online emulator developed by retro hacker [Andy Toone].

We wrote about the 6502-based ERIC-1 project back in 2014 which shared the bus with an ATMEGA simulating ROM. The Minty Z80 project from 2019 also uses a similar technique. Thanks to [Frédéric] for sending us the tip.

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An ALU As A Desktop Calculator Has Stunning Style From Days Gone By

June 7, 2021 by Jenny List 9 Comments

Those of you with an interest in microcomputer history will know that there is a strong crossover between the path of electronic calculator evolution and the genesis of the integrated CPU. Intel’s 4000 was famously designed for a calculator, and for a while in the 1970s these mathematical helpers were seen as the wonder of the age. [Simon Boak]’s calculator is a curious throwback to that era, as it’s not a decimal calculator as we’d know it but a hexadecimal device that simply computes using the functions of the famous 74181 ALU chip.

An ALU, or to give it its full name an Arithmetic Logic Unit, is a component of a CPU with two inputs and one output that can perform any of a range of binary functions upon the two inputs and return the result on the output. This calculator has two of them for eight bits of raw adding power, with a hexadecimal keypad for setting the inputs and a set of 7-segment displays for showing the results. It’s housed in an achingly retro folded sheet metal console case with wooden end pieces that would have graced any engineer’s desk with pride back in about 1975. We may not need one, but we really want one!