It would be an understatement to say that the Commodore 64 demo scene is quite amazing. For those who are unaware, a ‘demo’ in this context is essentially a technological demonstration. Usually to show off particular effects or other (visual) properties that either push the limits of the platform on which it is being run, or use its hardware in a special fashion. In the case of [Linus Åkesson]’s A Mind Is Borndemo, the challenge was to do as much as possible in 256 bytes, while providing an audiovisual experience.
Although at first glance 256 bytes may sound like a lot to work with, this code has to generate the entire melody that is output via the Commodore 64’s SID audio chip, while simultaneously generating an attractive visual pattern. This is quite an undertaking, as the video capture of the result (included after the break) makes clear. The secret sauce here is to make use of the C64’s SID audio & VIC-II video chips.
Driven by a 60 Hz timer interrupt, the three voices of the SID are used to play the kick drum and bass, melody and drone respectively, creating the 64 total bars of the music using a linear-feedback shift register (LFSR). This means that the melody is in a sense randomly generated, but deterministically enough to sound pleasing to the human ear.
For the visual side, the C64 runs in Extended Character Mode, using fonts along with a background color to create interesting patterns using what is essentially a cellular automaton algorithm. While there are some visual glitches due overwriting of video data, and a race condition, these end up adding to the charm. The resulting audio track is pretty catchy too, and absolutely worthy of a listen.
The demo code for [XTronical]’s ESP32-based SD card music player is not even 40 lines long, though it will also require a few economical parts before it all works. Nevertheless, making a microcontroller play MP3s (and other formats) from an SD card is considerably simpler today than it was years ago.
Part of what makes this all work is I2S (Inter-IC Sound), a format for communicating PCM audio data between devices. Besides the ESP32, at the heart of it all is an SD card reader breakout board and the MAX98357A, which can be thought of as a combination I2S decoder and Class D amplifier. The ESP32 reads audio files from the SD card and uses an I2S audio library to send the I2S data stream to the MAX98357A (or two of them for stereo.) From there it is decoded automatically and audio gets pumped though attached speakers.
It’s amazing how much easier audio is to work with when one can take advantage of shuffling audio data around digitally, and the decoder handles multiple formats with an amplifier built in. You can see [XTronical]’s ESP32 player in action in the video embedded below.
In 1993, IBM PCs & clones were a significant but not dominant fraction of the home computer market. They were saddled with the stigma of boring business machines. Lacking Apple Macintosh’s polish, unable to match Apple II’s software library, and missing Commodore’s audio/visual capabilities. The Amiga was the default platform of choice for impressive demos, but some demoscene hackers saw the PC’s potential to blow some minds. [Future Crew] was such a team, and their Second Reality accomplished exactly that. People who remember and interested in a trip back in time should take [Fabien Sanglard]’s tour of Second Reality source code.
We recently covered another impressive PC demo executed in just 256 bytes, for which several commenters were thankful the author shared how it was done. Source for demos aren’t necessarily released: the primary objective being to put on a show, and some authors want to keep a few tricks secret. [Future Crew] didn’t release source for Second Reality until 20th anniversary of its premiere, by which time it was difficult to run on a modern PC. Technically it is supported by DOSBox but rife with glitches, as Second Reality uses so many nonstandard tricks. The easiest way to revisit nostalgia is via video captures posted to YouTube (one embedded below the break.)
A PC from 1993 is primitive by modern standards. It was well before the age of GPUs. In fact before any floating point hardware was commonplace: Intel’s 80387 math co-processor was a separate add-on to the 80386 CPU. With the kind of hardware at our disposal today it can be hard to understand what a technical achievement Second Reality was. But PC users of the time understood, sharing it and dropping jaws well beyond the demoscene community. Its spread was as close to “going viral” as possible when “high speed data” was anything faster than 2400 baud.
“Revision” is probably the Olympics of the demoscene. The world’s best tiny graphics coders assemble, show off their works, and learn new tricks to pack as much awesome into as few bytes as possible or make unheard-of effects on limited hardware. And of course, there’s a competition. Winning this year’s 256-byte (byte!) competition, and then taking the overall crowd favorite award, was [HellMood]’s Memories.
If you watch it in the live-stream from Revision, you’ll hear the crowd going (virtually) wild, and the announcer losing his grip and gasping for words. It’s that amazing. Not only are more effects put into 28 bytes than we thought possible, but there’s a full generative MIDI score to go with it. What?!?
But almost as amazing is [HellMood]’s generous writeup of how he pulled it off. If you’re at all interested in demos, minimal graphics effects, or just plain old sweet hacks, you have your weekend’s reading laid out for you. [HellMood] has all of his references and influences linked in as well. You’re about to go down a very deep rabbit hole.
Moore’s law may have reached its physical limit for transistor density, but plenty of other technologies are still on that familiar path of getting smaller and smaller as time passes. It looks like LIDAR is no exception to this trend either. This project from [Owen] shows a fully-functional LIDAR system for about $20 and built almost entirely on top of an ESP32.
The build uses a Time-Of-Flight IR laser range sensor controlled by the ESP32, and the sensor is much smaller than even the ESP32’s footprint so it takes up very little extra space. To get it to function as a LIDAR system instead of just a simple rangefinder it does need a motor in order to rotate itself to see its entire space. Besides its small form factor and low cost, it also has a handy user interface that can run anywhere an HTML5 browser can run, making the use of the system easy and straightforward as well. All of the code is available on the project’s GitHub page.
We wouldn’t expect a system like this to be driving an autonomous car anytime soon, it’s update rate is far too slow, but its intent for small robots and even as an educational demo for learning LIDAR is second to none. If you do need a little more power in a LIDAR system but still don’t want to break the bank, we featured this impressive setup a few weeks ago.
If you’re like us, understanding the processes and methods of the early Industrial Revolution involved some hand waving. Take the blast furnace, which relies on a steady supply of compressed air to stoke the fire and supply the oxygen needed to smelt iron from ore. How exactly was air compressed before electricity? We assumed it would have been from a set of bellows powered by a water wheel, and of course that method was used, but it turns out there’s another way to get compressed air from water: the trompe.
As [Grady] from Practical Engineering explains in the short video below, the trompe was a clever device used to create a steady supply of high-pressure compressed air. To demonstrate the process, he breaks out his seemingly inexhaustible supply of clear acrylic piping to build a small trompe. The idea is to use water falling around a series of tubes to create a partial vacuum and entrain air bubbles. The bubbles are pulled down a vertical tube by the turbulence of the water, and then enter a horizontal section where the flow evens out. The bubbles rise to the top of the horizontal tube where they are tapped off by another vertical tube, as the degassed water continues into a second vertical section, the height of which determines the pressure of the stored air. It’s ingenious, requiring no power and no moving parts, and scales up well – [Grady] relates a story about one trompe that provided compressed air commercially for mines in Canada.
Need an electricity-free way to pump water instead of air? Check out this hydraulic ram pump that takes its power from the water it pumps.
There’s plenty of juicy reading material here. There are palette hacks to produce high-quality greyscale images, rendering tips to produce the smooth 3D rendered sequences, as well as optimizations to create the best possible sample playback using the onboard YM2612 sound chip. It’s a tour de force of development, and it’s astounding to look behind the curtain to see just what can be achieved.