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Tiny Tapeout 4: A PWM clone of Covox Speech Thing

21 Junio 2024 at 20:00

Tiny Tapout is an interesting project, leveraging the power of cloud computing and collaborative purchasing to make the mysterious art of IC design more accessible for hardware hackers. [Yeo Kheng Meng] is one such hacker, and they have produced their very first custom IC for use with their retrocomputing efforts. As they lament, they left it a little late for the shuttle run submission deadline, so they came up with a very simple project with the equivalent behaviour of the Covox Speech Thing, which is just a basic R-2R ladder DAC hanging from a PC parallel port.

The computed gate-level routing of the ASIC layout

The plan was to capture an 8-bit input bus and compare it against a free-running counter. If the input value is larger than the counter, the output goes high; otherwise, it goes low. This produces a PWM waveform representing the input value. Following the digital output with an RC low-pass filter will generate an analogue representation. It’s all very simple stuff. A few details to contend with are specific to Tiny Tapout, such as taking note of the enable and global resets. These are passed down from the chip-level wrapper to indicate when your design has control of the physical IOs and is selected for operation. [Yeo] noticed that the GitHub post-synthesis simulation failed due to not taking note of the reset condition and initialising those pesky flip-flops.

After throwing the design down onto a Mimas A7 Artix 7 FPGA board for a quick test, data sent from a parallel port-connected PC popped out as a PWM waveform as expected, and some test audio could be played. Whilst it may be true that you don’t have to prototype on an FPGA, and some would argue that it’s a lot of extra effort for many cases, without a good quality graphical simulation and robust testbench, you’re practically working blind. And that’s not how working chips get made.

If you want to read into Tiny Tapeout some more, then we’ve a quick guide for that. Or, perhaps hear it direct from the team instead?

BASIC Classroom Management

25 Mayo 2024 at 11:00

While we don’t see it used very often these days, BASIC was fairly revolutionary in bringing computers to the masses. It was one of the first high-level languages to catch on and make computers useful for those who didn’t want to (or have time) to program them in something more complex. But that doesn’t mean it wasn’t capable of getting real work done — this classroom management software built in the language illustrates its capabilities.

Written by [Mike Knox], father of [Ethan Knox] aka [norton120], for his classroom in 1987, the programs were meant to automate away many of the drudgeries of classroom work. It includes tools for generating random seating arrangements, tracking attendance, and other direct management tasks as well as tools for the teacher more directly like curving test grades, tracking grades, and other tedious tasks that normally would have been done by hand at that time. With how prevalent BASIC was at the time, this would have been a powerful tool for any educator with a standard desktop computer and a floppy disk drive.

Since most people likely don’t have an 80s-era x86 machine on hand capable of running this code, [Ethan] has also included a docker container to virtualize the environment for anyone who wants to try out his father’s old code. We’ve often revisited some of our own BASIC programming from back in the day, as our own [Tom Nardi] explored a few years ago.

Hackaday Links: May 5, 2024

5 Mayo 2024 at 23:00
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It may be hard to believe, but BASIC turned 60 this week. Opinions about the computer language vary, of course, but one thing everyone can agree on is that Professors Kemeny and Kurtz really stretched things with the acronym: “Beginner’s All-Purpose Symbolic Instruction Code” is pretty tortured, after all. BASIC seems to be the one language it’s universally cool to hate, at least in its current incarnations like Visual Basic and VBA. But back in 1964, the idea that you could plunk someone down in front of a terminal, or more likely a teletype, and have them bang out a working “Hello, world!” program with just a few minutes of instruction was pretty revolutionary. Yeah, line numbers and GOTO statements encouraged spaghetti code and engrained bad programming habits, but at least it got people coding. And perhaps most importantly, it served as a “gateway drug” into the culture for a lot of us. Many of us would have chosen other paths in life had it not been for those dopamine hits provided by getting that first BASIC program working. So happy birthday BASIC!

Speaking of gateways, we’ve been eagerly following the “65 in 24” project, an homage to the “65 in 1” kits sold by Radio Shack back in the day. These were the hardware equivalent of as BASIC to a lot of us, and just as formative. Tom Thoen has been lovingly recreating the breadboard kit, rendering it in PCBs rather than cardboard and making some updates in terms of components choices, but staying as true to the original as possible. One thing that the original had was the “lab manual,” a book containing all 65 circuits with schematics and build instructions, plus crude but charming cartoons to illustrate the principles of the circuit design. Tom obviously needs to replicate that to make the project complete, and while schematics are a breeze in the age of EDA, the cartoons are another matter. He’s making progress on that front, though, with the help of an art student who is really nailing the assignment. Watch out, Joe Kim!

Last week we mentioned HOPE XV is coming in July. This week, a partial list of talks was released, and there’s already a lot of interesting stuff scheduled. Supercon keynote alums Mitch Altman and Cory Doctorow are both scheduled to appear, along with a ton of others. Check out the list, get your proposals in, or just get your tickets.

If an entire forest is composed of a single tree, does it make a sound? Yes it does, and it’s kind of weird. The tree is called Pando, which is also weird, and it’s the largest living individual organism by biomass on Earth. The quaking aspen has 47,000 stems covering 100 acres (40 hectares) of Utah, and though it does a pretty good job of looking like a forest, the stems are genetically identical so it counts as a single organism. Quaking aspens are known to be a noisy tree, with leaves that rattle together in the slightest breeze. That pleasant sound isn’t just for us to enjoy, however, as sound artist Jeff Rice discovered by sticking a hydrophone down into one of Pando’s many hollow stems. The sound of the leaves banging together apparently gets transmitted down the stems and into the interconnected root system. At least that’s the thought; more rigorous experiments would be needed to confirm that the sound isn’t being mechanically coupled through the soil.

And finally, we’re in no position to cast stones at anyone for keeping a lot of browser tabs open, but keeping almost 7,500 Firefox tabs going seems a bit extreme. And yet a software engineer going by the handle Hazel just can’t bring herself to close any tabs, resulting in an epic restore session when her browser finally gave up the ghost. Panic set in at first when Firefox refused to reload all the tabs, accumulated over the last two years, but eventually the browser figured it all out and Hazel was back in business. Interestingly, Firefox doesn’t really use up too much memory to keep al those tabs open — only 70 MB. Compare that to Chrome, which needs 2 GB to keep a measly 10 tabs open.

You Can Run BASIC On an Old HP 4592 Protocol Analyzer

Por: Lewin Day
28 Abril 2024 at 20:00

What do you do when you find an ancient piece of test gear and want to have fun? Well, you can always try getting BASIC running on it, and that’s precisely what [David Kuder] did.

The HP4952A Protocol Analyzer actually looks a lot like an old computer, even if it was never meant for general-purpose use. The heart of the machine is a Zilog Z80 CPU, though, so it shares a lot in common with microcomputers of its era.

Among other hacks, [David] worked to get Microsoft Basic-80 running on the machine. Initially, he was only able to get it up and running on the display, with no way to read the keyboard, disk, or access the serial port. Eventually, by diving into the nitty-gritty of the machine, he was able to at least get the keyboard working along with some basic BASIC programs. Usable memory is just 8KB, but you can do a fair bit with that when you’ve only got a 32×16 display for output anyway!

It’s a neat hack and one that was extendable to the HP4957A as well. We’ve seen similar machines on these pages before, too! If you’ve got your own neat retro hacks on the boil, don’t hesitate to drop us a line!

[Thanks to Christopher Zell for the tip!]

The Z80 Is Dead. Long Live The Free Z80!

Por: Jenny List
28 Abril 2024 at 11:00

It’s with a tinge of sadness that we and many others reported on the recent move by Zilog to end-of-life the original Z80 8-bit microprocessor. This was the part that gave so many engineers and programmers their first introduction to a computer of their own. Even though now outdated its presence has been a constant over the decades. Zilog will continue to sell a Z80 derivative in the form of their eZ80, but that’s not the only place the core can be found on silicon. [Rejunity] is bringing us an open-source z80 core on real hardware, thanks of course to the TinyTapeout ASIC project. The classic core will occupy two tiles on the upcoming TinyTapeout 7. While perhaps it’s not quite the same as a real 40-pin DIP in your hands, like all of the open-source custom silicon world, it’s as yet early days.

The core in question is derived from the TV80 open-source core, which we would be very interested to compare when fabricated at TinyTapeout’s 130nm process with an original chip from a much larger 1970s process. While It’s true that this project is more of an interesting demonstration of TinyTapeout than a practical everyday Z80, it does at least serve as a reminder that there may be a future point in which a run of open-source real Z80s or other chips might become possible.

This isn’t the first time we’ve featured a TinyTapeout project.

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