VGA Library For The Raspberry Pi Pico

June 11, 2021 by Chris Lott 11 Comments

[Miroslav Nemecek] really pushes the limits of the Pico with his PicoVGA project, which packs a surprising number of features. His main goal with this library is to run retro games which can fit within the limited RAM and processing power of the Pico, but the demo video below shows a wide array of potential applications.

The library provides a whole slew of features, including frame buffering, sprites, overlays, and resolutions up to 1280×960 in either NTSC or PAL timings. A PWM-driven audio output channel is also included in the package. His library takes full advantage of the programmable I/O module functionality and uses the second core which is dedicated to video processing. However, with care, the second core can perform application tasks in certain circumstances. The VGA analog output signals are provided by resistor ladders, and pixel color is 8-bit R3G3B2 format. To be clear, [Miroslav] does cheat a little bit here in one regard — he overclocks the processor up to 270 MHz to meet the timing demands in some of the resolutions.

[Miroslav] has developed these tools using ARM-GCC on Windows, but he lacks the experience to make a Linux build. He welcomes help on that front from anyone familiar with Linux. And stay tuned — there may be more coming from [Miroslav] in the future. He notes that the PicoVGA library was created as part of a retro gaming computer project which is still under development. We look forward to hearing more about this when it gets released.

A couple of weeks ago we wrote about a monochrome VGA version of Pong for the Pico by [Nick Bild]. It’s exciting to see these projects which are exploring the limits of the Pico’s capabilities. Have you seen any boundary-pushing applications for the Pico? Let us know in the comments below. Thanks to [Pavel Krivanek] for sending this project to our tip line.

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History Of Closed Captions: Entering The Digital Era

May 27, 2021 by Chris Lott 42 Comments

When you want to read what is being said on a television program, movie, or video you turn on the captions. Looking under the hood to see how this text is delivered is a fascinating story that stared with a technology called Closed Captions, and extended into another called Subtitles (which is arguably the older technology).

I covered the difference between the two, and their backstory, in my previous article on the analog era of closed captions. Today I want to jump into another fascinating chapter of the story: what happened to closed captions as the digital age took over? From peculiar implementations on disc media to esoteric decoding hardware and a baffling quirk of HDMI, it’s a fantastic story.

There were some great questions in the comments section from last time, hopefully I have answered most of these here. Let’s start with some of the off-label uses of closed captioning and Vertical Blanking Interval (VBI) data.

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Obsessively Explaining The Visual Effects In Flight Of The Navigator

May 26, 2021 by Zach Zeman 9 Comments

[Captain Disillusion] has earned a reputation on YouTube for debunking hoaxes and spreading a healthy sense of skepticism while having some of the highest production value on the platform and pretending to be some kind of inter-dimensional superhero. You’ve likely seen him give a careful explanation of how some viral video was faked alongside a generous dose of sarcastic humor and his own impressive visual effects. VFXcool is a series on his channel that takes deep dives into movies that are historically significant in the effects industry. For this installment, [Captain Disillusion]’s “intern”, [Alan], takes over to breakdown how filmmakers brought a futuristic spaceship to life in 1986’s Flight of the Navigator.

Making a movie requires hacks upon hacks, and that goes double in the era when the technology and techniques we now take for granted were being developed even as they were being put to film. The range of topics covered here is extreme: from full-scale props to models; from robotic motion control rigs to stop motion animation; from early computer graphics to the convoluted optical compositing that was necessary before digital workflows were possible. The tools themselves may be outdated, but understanding the history and the processes allows for a deeper insight into how we accomplish these kinds of effects today. And, really, it’s just so… cool.

[Captain Disillusion]’s previous VFXcool is all about the Back to the Future trilogy, and it’s a little shorter with more information on motion control rigs. We also love seeing how people make DIY effects in their own homes. LEGO actually seems like a pretty popular option for putting together whole scenes in amateur filmmaking.

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RAM Fiddling Turns VGA Converter Into Video Synth

May 25, 2021 by Tom Nardi 2 Comments

If you’re interested in circuit bent video but not sure where to start, the excellent guide [LoFi Future] has come up with for modifying the cheap and readily available GBS-8100 VGA to composite converter would be a great first step. While we wouldn’t call it an easy modification, the circuit documentation and demonstration video below go a long way to making it as accessible as possible to new players.

While other video converters have all-in-one chipsets that are much harder to work with, [LoFi Future] explains that the separate EM636165TS DRAM chip on the GBS-8100 provides an ideal spot to tap in and wreak some technicolor havoc. By mapping out the pins and studying how the video output is corrupted by grounding them out or connecting them to each other, he’s been able to come up with fairly repeatable “recipes” for different effects.

In the most basic form, once you’ve soldered the pins of the DRAM chip up to the plug board interface, you’d technically be done. But [LoFi Future] takes it a step further and pairs the GBS-8100 with a separate composite to VGA converter. This provides some additional effects in the form of feedback loops and hue adjustment, but more practically, allows the device to handle composite on both the input and output. It’s a lot of hardware to cram into the enclosure, but thanks to little touches like the printed panel graphics, the final product does looks very professional.

Aside from the occasional modified NES Zapper, most of the circuit bent hardware we see is of the audio variety. But with projects like this one and the MIDI controlled SNES we covered last year as inspiration, we might see a balancing of the scales. Continue reading “RAM Fiddling Turns VGA Converter Into Video Synth” →

Retro ISA Card Means Old, Slow Computers No Longer Need Old, Heavy Monitors

May 18, 2021 by Donald Papp 66 Comments

One thing about vintage computers is that they depend greatly on whether or not one can plug a compatible monitor into them. That’s what’s behind [Tube Time]’s Graphics Gremlin, a modern-design retro ISA video card that uses an FPGA to act just like a vintage MDA or CGA video card on the input end, but provides a VGA port for more modern display output options. (Actually, there is also an RGBI connector and a composite video out, but the VGA is probably the most broadly useful.)

Handy silkscreen labels make everything crystal clear. Click to enlarge.

Why bother making a new device to emulate an old ISA video card when actual vintage video cards are still plentiful? Because availability of the old cards isn’t the bottleneck. The trouble is that MDA or CGA monitors just aren’t as easy to come across as they once were, and irreplaceable vintage monitors that do still exist risk getting smashed during shipping. Luckily, VGA monitors (or at least converters that accept VGA input) are far more plentiful.

The board’s design files and assembly notes are all on the project’s GitHub repository along with plenty of thoughtful detail about both assembly and troubleshooting, and the Verilog code has its own document. The Graphics Gremlin is still under development, but you can also watch for the latest on [Tube Time]’s Twitter feed.

Thanks to [NoxiousPluK] for the tip!

Disgusting Apple II Monitors Live Again

May 17, 2021 by Chris Lott 33 Comments

[The 8-Bit Guy] recently went to check out a stash of old Apple II Color monitors which had been sitting outside in a trash pile for 20 years, and decided to bring one home to restore. As you can see from the lead photo, they were dirty — really dirty. Surprisingly, the team of volunteers who discovered these monitors had fired them up, and every one of them works to some extent or another.

Check out the video below as he cleans up this filthy monitor and starts troubleshooting. You’ll chuckle aloud when he turns the circuit board over to desolder a mysterious diode, and when he flips the board back over, the diode has disappeared (it actually disintegrated into dust on his lab bench). For the curious, one commenter on YouTube found that it was a glass passivated and encapsulated fast recovery diode called a V19. There’s going to be a part 2, and we have every confidence that [The 8-Bit Guy] will succeed and soon add a shiny, like-new monitor to his collection.

If you’re a collector of old monitors, this demonstrates that they can survive quite a bit of abuse and exposure. We’re not sure that rummaging through your local landfill is the best idea, but if you run into an old monitor that has been exposed to the elements, don’t be so quick to dismiss it as a lost cause. Do you have any gems that you’ve restored from the trash? Let us know in the comments.

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VGA Graphics Card In 74xx Logic

April 30, 2021 by Chris Lott 17 Comments

Feeling nostalgic we presume, [Glen Kleinschmidt] set out to build a 640x480x64 VGA controller card from discrete logic chips. If we ignore the 512Kx8 Cypress SRAM video memory, he succeeds, too — and on a very readable, single page A3 schematic. The goal is to interface some of his older 8-bit machines, like the TRS-80 Model 1 and the BBC Micro, but for now he’s running a demo using a 20+ year old PIC16F877 micro.

[Glen] provides all the schematics, Gerbers, and C source code on his website should you be inclined to reproduce one for yourself. He has three versions in the works, with various capabilities (there’s a table on his website). As an alternative, one could always use an FPGA or a custom-built chip such as the SSD1963 to generate video for these micros, but sometimes the urge to go retro is too great to resist. We get the feeling that for [Glen], this is a project unto itself, and being able to interface it to his 8-bit computers is just a convenient excuse.

This isn’t [Glen]’s first retro project, either. Check out his analog computer “bouncing ball” project we covered back in 2017. Have you struggled with the build vs. buy decision, and how do you decide?

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