classic hacks

2769 Articles

Arduino Revives A Classic 1980s Minitel Terminal

February 27, 2019 by 16 Comments

Before there was the Internet, there were a lot of would-be Internets. Compuserve comes to mind, as do Prodigy, GEnie, Delphi, and the innumerable BBS systems that were once gateways to worlds beyond our CRT monitors and 300 baud Hayes Supermodems.

Service providers varied by region, of course. The French postal and telephone service rolled out their service, Médium interactif par numérisation d’information téléphonique, in 1978. Mercifully and memorably shortened to Minitel, the service was originally intended primarily as an online telephone directory, and later expanded to include other services. [Kevin Driscoll] and [Julien Mailland] recently resurrected a Minitel terminal, a Videotex terminal that was the gateway to the service. The terminal they used, a model 1B, is a stylish machine with a monochrome CRT display and compact “AZERTY” keyboard. [Kevin] and [Julien] built a Videotex server for it using an Uno and a logic-level converter to keep the two talking. Using the hardware, they’ve developed a Twitter client, a webcam display, and dumb Linux terminal.

[Julien] and  [Kevin] previously authored a great history of Minitel that’s worth a read. And we’ve seen a few Minitel hacks before, including converting one to USB for use as a Raspberry Pi terminal.

Teach Computing The Old-School Way With A Digi-Comp II

February 25, 2019 by 8 Comments

Ubiquitous computing has delivered a world in which there seem to be few devices left that no longer contain a microprocessor of some sort. Thus should a student wish to learn about the inner workings of a computer they can easily do so from a multitude of devices. For an earlier generation though this was not such a straightforward process, in the 1950s or 1960s you could not simply buy a microcomputer and set to work. Instead a range of ingenious teaching aids providing the essentials of computing without a computer were created, and those students saw their first computational logic through the medium of paper, ball bearings, or flashlight bulbs.

The DigiComp II was just such a device, performing logic tasks through ball bearings rolling down trackways. Genuine machines are now particularly rare, so [Mike Gardi] created a modern 3D printed replica that delivers all the fun without the cost. It’s a complicated build with a multitude of parts and wire linkages, and there is an element of fine tuning of its springs required to achieve reliable operation. You’ll neither run a Beowulf cluster of DigiComp IIs nor will you mine any Bitcoin with one, but it’s definitely one of the more unusual computing devices you could have in your collection.

Of course, should you need a truly authentic period computing device, there is always the slide rule.

Via Hacker News.

Curve Tracing On Spray Painted CRTs

February 24, 2019 by 16 Comments

A Lissajous curve is formed when two sine waves plotted on their respective X and Y axes. You can see one using an oscilloscope and a couple of signal generators, if you play with one of those ‘pendulums tracing in the sand’ toys, or if you really need something sciencey for your home decor you can trace them out with a disassembled CRT. That’s what [Emily] did with the LissaJukebox. It traces curves. No, it’s not a curve tracer, that’s another tool altogether

If you’re going to put squigglies on a CRT, you obviously need a CRT, and it needs to look good. There are a few options out there, from old oscilloscope tubes, the CRTs found in old VHS camcorders, to tiny electrostatic tubes that are slightly easier to drive. For this build, [Emily] chose an old, bog-standard, black and white television. But the screen is green, right? Yeah, but if you carefully mask off a CRT and buy some stained glass spray paint, a CRT can be any color you want. Except for purple, the purple stained glass spray paint didn’t work for some reason.

To generate the various functions, [Emily] used an XR2206 function generator, sold in kit form on Amazon, eBay, and various other online retailers for a pittance. One of these function generators controls the X axis, another the Y, and both of these generators are fed into a 15 Watt stereo amplifier board to run the deflection coils in the CRT. If you’re following along at home, yes, this is dangerous. Don’t touch the CRT or it will stop your heart. Those of us whose hearts are as black as coal are safe.

There were a few modifications needed to turn the XR2206 function generator ‘kit’ into something a bit more useful for this project. The through-hole pots were replaced with panel-mount pots, and the range/amplitude setting is now controlled with a rotary switch.

Is it useful? Well, actually, if you’re building a set for a TV show and you need something that looks ‘sciencey’, a LissaJukebox should be right up your alley. Other than that it looks pretty, and we now know there’s a spray paint that will turn your old, boring black and white CRT into a glorious amber phosphor. Can’t beat that.

DAT, The HD Video Tape Format We Never Knew We Had

February 24, 2019 by 48 Comments

When we consume our music online via streaming services it is easy to forget the days of recordings being contained on physical media, and to overlook the plethora of competing formats that vied for space in our hi-fi systems to play them. [Andrew Rossignol] has an eye for dated recording media formats as a chiptune enthusiast though, because not only has he found a DAT machine from the 1990s, he’s hacked it to record HD video rather than hi-fi audio.

If you’ve not encountered DAT before, it’s best to consider the format as the equivalent of a CD player but on a tape cassette. It had its roots in the 1980s, and stored an uncompressed 16-bit CD-quality stereo audio data stream on the tape using a helical-scan mechanism similar to that found in a video cassette recorder. It was extremely expensive due to the complexity of the equipment, the music industry hated it because they thought it would be used to make pirate copies of CDs. But despite those hurdles it established a niche for itself among well-heeled musicians and audiophiles. If any Hackaday readers have encountered a DAT cassette it is most likely to have not contained audio at all but computer data, it was common in the 1990s for servers to use DAT tapes for backup purposes.

[Andrew]’s hack involves using the SPDIF digital interface on his Sony DAT player to carry compressed video data. SPDIF is a mature and well-understood standard that he calculated has a bandwidth of 187.5 kB/s, plenty to carry HD video using the H.265 compression scheme. The SPDIF data is brought into the computer via a USB sound card, and from there his software could either stream or retrieve the video. The stream is encoded into frames following the RFC1662 format to ensure synchronization, and he demonstrates it in the video below with a full explanation.

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Flying Convenience Not So Convenient

February 23, 2019 by 19 Comments

It’s a situation that plays out every day, all over the world – you walk into work, and there’s a full-scale foam toilet sitting on the bench, demanding to be used in a crackpot project. This time, it happened to be at the [FliteTest] workshop, and naturally, they set about making it fly.

The team at [FliteTest] are well resourced, with a laser cutter being used to quickly produce a set of custom foam board wings. However, after wing failures on their previous projects, this time the team opted for a riveted aluminium wing spar to add strength. A twin-boom tail is used to try to avoid the cistern from interfering with airflow over the elevator, and careful attention is paid to make sure the center of gravity is in the right position for stable flight.

Despite the team’s laudable efforts, the toilet (somewhat unsurprisingly) flies like crap. It just goes to show, you can strap a brushless power system on to just about anything, but aerodynamics will still be standing ready to bring it all crashing down to Earth.

We’ve seen some great builds from [FliteTest] over the years – before the throne, it was an IKEA chair that soared amongst the clouds. Video after the break.

[Thanks to Baldpower for the tip!] Continue reading “Flying Convenience Not So Convenient” →

Charging LiPos With USB Power Delivery

February 23, 2019 by 2 Comments

DC power bricks were never a particularly nice way to run home electronics. Heavy and unwieldy, they had a tendency to fall out and block adjacent outlets from use. In recent years, more and more gadgets are shipping with USB ports for power input. However, power over USB has always been fraught with different companies using all manner of different methods to communicate safe current limits between chargers and hardware.

These days, we’re lucky enough to have the official USB Power Delivery standard in place. Even laptop chargers are using USB now, and [FPVtv DRONES] decided to see if it was possible to use such a device as a high current power supply to charge batteries.

The test starts with a MI brand USB C laptop charger. A USB power meter is plugged inline to determine voltage and current output of the charger, while a small microcontroller device is used to speak with the laptop charger and set it to high voltage, high current delivery mode. A lithium battery charger is then plugged in, and the setup is tested by charging two large 4-cell LiPos at over 1.4 amps concurrently.

The setup demonstrates that, with the right off-the-shelf modules, it’s possible to use your laptop charger to run high-current devices, as long as you can spoof it into switching into the right mode. This is the natural evolution of USB power technology – a road which started long ago with projects like the MintyBoost, way back when. Video after the break.

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The PC Speaker Lives On As A New Album

February 23, 2019 by 25 Comments

The speaker in the original IBM PC is nearly the worst electronic musical instrument ever created. This isn’t because amazing works of art were never created for the PC speaker; no, that’s been done, and it’s amazing. The PC speaker is terrible because of how limited it is. It does one note at a time, only square waves, driven by an 8253 Programmable Interval Timer. Polyphony? Forget about it. Volume control? Nope. These aren’t really shortcomings, because music is art, and you can write a novel without using the letter ‘E’; the trick is in how you manage to do it.

[shiru8bit] took a deep dive into the PC speaker and decided to make an album. The video, with the completely necessary CRT graphic display, can be seen here. This alone is impressive, but what makes it amazing is how this album happened.

If you want to play more than a simple melody on a PC speaker, there are two or two and a half ways to do it. The first is to (virtually) set up two (or more) channels, loaded up with frequency values. At set intervals, the CPU changes the 8253 to output one frequency, then in the next chunk of time, sets the 8253 to another frequency. It sounds ‘bubbly’ for lack of a better term, but the results can be amazing; just check out the PC speaker version of Monkey Island. The 8253 can also be turned into a rudimentary DAC, but this was a rare technique thanks to patents, and by the time the patents expired everyone already had a Soundblaster. Oh well.

[shiru8bit]’s album uses the first technique, cycling through monophonic square waves at 120 Hz, but the real trick here is how the individual channels were composed. This required creating a VSTi plugin called PCSPE. This emulates a PC speaker, and sort of, kind of, implements arpeggios, pitch, and priority of different channels. Effectively, it’s a PC Speaker tracker.

The result is classic chiptune goodness, made on an instrument that really shouldn’t be used for music. It can be played on DosBox, but the weirdness of the real hardware including transients and the inefficiencies of a tiny speaker make real hardware almost a necessity here. You can check out the entire album below.

Continue reading “The PC Speaker Lives On As A New Album” →