Not All Raspberry Pi Laptops Have QWERTY Keyboards And Screens

Our recent coverage of a Raspberry Pi Zero inside the official Pi keyboard prompted a reader to point us to another far more unusual keyboard with a Pi Zero inside it. It may be a couple of years old, but [Mario Lang]’s Braille keyboard and display with built-in Pi is still an interesting project and one that should give sighted readers who have not encountered a Braille display an introduction to the technology.

The model in question is a Handy Tech Active Star 40, which seems to have been designed to have a laptop sit on top of it. A laptop was not the limit of its capabilities, because it also has a compartment with a handy USB connector that was intended to take a smartphone and thus makes a perfect receptacle for a Pi Zero. Sadly the larger boards are a little tall with their connectors.

If this hack were preformed today he would undoubtedly have used a Pi Zero W, but since the Zero he had did not possess WiFi he relied upon a Bluetooth dongle for connectivity to the outside world. The BRLTTY screen reader provides a Braille interface to the Linux console, resulting in an all-in-one Braille computer in a very compact form factor.

This is one portable Braille computer, but it’s by no means the only one we’ve seen. Thanks [Simon Kainz] for the tip, and here’s a nod to the Pi keyboard that inspired him.

How The Gigatron TTL Microcomputer Works

About a year ago when Hackaday and Tindie were at Maker Faire UK in Newcastle, we were shown an interesting retrocomputer by a member of York Hackspace. The Gigatron is a fully functional home computer of the type you might have owned in the early 1980s, but its special trick is that it does not contain a microprocessor. Instead of a 6502, Z80, or other integrated CPU it only has simple TTL chips, it doesn’t even contain the 74181 ALU-in-a-chip. You might thus expect it to have a PCB the size of a football pitch studded with countless chips, but it only occupies a modest footprint with 36 TTL chips, a RAM, and a ROM. Its RISC architecture provides the explanation, and its originator [Marcel van Kervinck] was recently good enough to point us to a video explaining its operation.

It was recorded at last year’s Hacker Hotel hacker camp in the Netherlands, and is delivered by the other half of the Gigatron team [Walter Belgers]. In it he provides a fascinating rundown of how a RISC computer works, and whether or not you have any interest in the Gigatron it is still worth a watch just for that. We hear about the design philosophy and the choice of a Harvard architecture, explained the difference between CISC and RISC, and we then settle down for a piece-by-piece disassembly of how the machine works. The format of an instruction is explained, then the detail of their 10-chip ALU.

The display differs from a typical home computer of the 1980s in that it has a full-color VGA output rather than the more usual NTSC or PAL. The hardware is simple enough as a set of 2-bit resistor DACs, but the tricks to leave enough processing time to run programs while also running the display are straight from the era. The sync interval is used to drive another DAC for audio, for example.

The result is one of those what-might-have-been moments, a glimpse into a world in which RISC architectures arrived at the consumer level years earlier than [Sophie Wilson]’s first ARM design for an Acorn Archimedes. There’s no reason that a machine like this one could not have been built in the late 1970s, but as we know the industry took an entirely different turn. It remains then the machine we wish we’d had in the early 1980s, but of course that doesn’t stop any of us having one now. You can buy a Gigatron of your very own, and once you’ve soldered all those through-hole chips you can run the example games or get to grips with some of the barest bare-metal RISC programming we’ve seen. We have to admit, we’re tempted!

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A Z80 Homebrew Console, With A Bit Of Modern Help

We see a lot of retrocomputing projects here at Hackaday that take devices from the 8-bit era and re-create them in the 21st century. Sometimes they remain period-accurate and stick to all contemporary devices, but in other cases they take full advantage of four decades of advancing technology. [Pkiller]’s Z80 console is one of this later category, creating peripherals for the classic CPU using microcontrollers in the place of the banks of 74 logic or ULA chips that might have graced a 1980s machine.

The video generation hardware produces a PAL signal using an interesting technique involving two RAM buffers. An ATmega644 microcontroller composites a single frame into one of the buffers while another ATmega644 is generating the previous frame of video from the other buffer. On each change of frame the buffers are switched between the two microcontrollers, requiring some extra 74 logic chips. Another AtMega chip provides the Z80 with I/O interfacing, and the sound comes via another dual-buffer microcontroller setup and a quick return to classic hardware with a YM3438 FM synthesis chip. The result can be seen in the video below, and would have not looked out of place in a late-’80s or even early-’90s living room.

Some people might ask why so much trouble should be gone to in the pursuit of a project like this one, but to do so is to miss the point. Sure, a Sega Master System can be had from the usual sources, but in creating  project such as this one the builder has to truly understand the technologies such as PAL generation or the internals of a Z80 in great detail. The result while it is undeniably impressive is almost secondary to the process of reaching it.

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A Ruined Saw Blade Becomes A Bowl

Every workshop generates waste, whether it be wood shavings, scrap metal, or fabric scraps, and sometimes that waste seems too good to throw away. [Igor Nikolic]’s hackerspace had a ruined circular saw blade in the trash, and rather than let it go to waste he took it to the forge and fashioned a bowl from it. Then because another blade came his way and he wasn’t quite happy with the first one, he made another.

The second of the two bowls, in its finished state.
The second of the two bowls, in its finished state.

Saw blades are not promising material for forge work, being made of a very high-quality hardened steel they do not take well to hammering even when hot. So his first task was to anneal his blade in a kiln, heating it up and then letting it cool slowly to soften it.

Working the blade into a bowl shape was done on a home-made ball anvil. The blade was marked to provide guide rings as an aid to forming, and the bowl shape was progressively built out from the center. The first bowl was a little irregular, in his second try he’d got into his stride. Both bowls were mounted, one on a cut acrylic base, the other on a set of feet.

A project such as this can only be done with a huge amount of work, for which owners of larger forges will typically use a power hammer. [Igor] admits that a swage block (a specialized anvil for forming such curved shapes) would have made his life easier, but we think he’s done a pretty good job.

If you’ve been paying attention to recent Hackaday articles you may have noticed the start of our series on blacksmithing. We’re indebted to [Igor] for the genesis of that piece, for he was operating the portable forge that features in it.

Make Your Commodore 16 64k, But Not A Commodore 64

The Commodore 16 was a budget home computer from the mid 1980s, the entry-level model in a wider range of machines. As its name suggests it only has 16k of memory in keeping with its budget status, and while it has the rest of the hardware necessary to run software intended for its 64k stablemates, that 16k is impossible to expand without modifying the machine. Should you have a ’16 in your collection this is not a particularly arduous process, and Tynemouth Software have gone into great detail over how it can be achieved.

As was quite common in machines of the period, the address lines for the RAM area above the fitted 16k are not wired to disable it when those addresses are selected, so the same 16k appears mirrored three times in the space between it and the 64k limit. Thus simply plugging in a 64k cartridge would result in the top 48k being unusable, and some means of disabling or supplanting the internal chips was called for. Contemporary upgrades required pin or track snipping, but as they go on to show us there are some less ugly alternatives both permanent and reversible. Whichever you might favor they all at least don’t carry the huge cost hurdle in 2019 that they might have been when the machine was new. Sadly even though their cases may be similar the resulting machine will not be a Commodore 64, not even a new one.

Long-time Hackaday readers will know that the hardware designer for these machines was our Hackaday colleague [Bil Herd], and all followers of Commodore and his work should read his account of the CES trade show at the heady height of Commodore’s  fame.

Show Your Skills With A Bootable CV

It’s a thankless task, searching for a job. You send off your CV, or resume, and it joins a thousand other destined for the round file. What on earth can you do to make your career stand out, and catch the eye of the recruiter?

Your bootable CV isn't eye-catching if the recruiter uses GitHub to view the PDF.
Your bootable CV isn’t eye-catching if the recruiter uses GitHub to view the PDF.

If you are [Pablo Jiménez Mateo], the answer is straightforward enough. Simply combine the document as a PDF with an x86 bootloader, to make a readable document that will also boot an x86 computer system. He can do this relatively easily by prepending the bootloader file to the PDF, as long as the “%PDF” header of the CV remains within the first 1024 bytes it will remain a readable document. Which it does, though as our GitHub screenshot shows, not in all PDF readers.

A bootable PDF is pretty cool and we have to salute his effort in getting it in front of us in the hope of  career boost, but it would be fair to admit that it’s a trick that has been done before. So it’s time to turn attention to the bootloader itself, whose code comes in the form of an extremely well-commented assembly file that loads some sprites and a border to a VGA screen that looks as though it might be the first room in a top-down adventure game. Through the code we can gain an appreciation of just how simple a bootloader can be, and that in itself makes this project worth a second look.

If writing your own bootloader interests you, that’s certainly a subject we’ve covered in the past. It’s possible to make bootable images very small indeed, even down to fitting in a Tweet.

Retrotechtacular: Nellie The School Computer

When did computers arrive in schools? That should be an easy question to answer, probably in the years around 1980. Maybe your school had the Commodore Pet, the Apple II, or if you are British, the Acorn BBC Micro in that period, all 8-bit microcomputers running a BASIC interpreter. That’s certainly the case for the majority of schools, but not all of them. In early 1969 the BBC’s Tomorrow’s World visited a school with a computer, and in both technology and culture it was a world away from those schools a decade later that would have received those BBC Micros.

The school in question was The Forrest Grammar School, Winnersh, about 35 miles west of London, and the computer in question was a by-then-obsolete National Elliott 405 mainframe that had been donated four years earlier by the British arm of the food giant Nestlé. The school referred to it as “Nellie” — a concatenation of the two brand names. It seems to have been the preserve of the older pupils, but the film below still shows the concepts of its operation being taught at all levels. We get a brief look at some of their software too — no operating systems here, everything’s machine code on paper tape — as a teacher plays a reaction timer game and the computer wins at noughts and crosses (tic-tac-toe). One of them has even written a high-level language interpreter on which younger children solve maths problems. Of course, a 1950s mainframe with hundreds or thousands of tubes was never a particularly reliable machine, and we see them enacting their failure routine, before finally replacing a faulty delay line.

This is a fascinating watch on so many levels, not least because of its squeaky-clean portrayal of adolescent boys. This is what teenagers were supposed to be like, but by the late 1960s they must in reality have been anything but that away from the cameras. It’s a contrast with fifteen or twenty years later, the computer is seen as an extremely important learning opportunity in sharp opposition to how 8-bit computers in the 1980s came to be seen as a corrupting influence that would rot young minds.

Of course, these youngsters are not entirely representative of British youth in 1969, because as a grammar school the Forrest was part of the top tier of the selective education system prevalent at the time. There would certainly have been no computers of any sort in the local Secondary Modern school, and probably the BBC’s portrayal of the pupils would have been completely different had there been. In 1974 the Government abolished the grammar school system to create new one-size-fits-all comprehensive schools, one of which the Forrest school duly became. Following the vagaries of educational policy it is now an Academy, and there is probably not a room within it that does not contain a computer.

So what of Nellie? Because of the film there are plenty of online references to it in 1969, but we could only find one relating to its fate. It was finally broken up in 1971, with the only surviving component being a delay line. More than one Elliott machine survives in museum collections though, and your best chance in the UK of seeing one is probably at the National Museum Of Computing, in Bletchley.

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