An Atari Graphics Chip, Ready For You To Build

The most notable of the home computer and console hardware from the 8-bit golden era didn’t get their impressive sound and graphics from off-the-shelf silicon, instead they relied on secretive custom chipsets to get the edge over their competitors. Unfortunately for vintage gaming aficionados, those chips are now long out of production and in many cases there’s little information to be had about their operation.

Which makes discovery of the schematics (PDF link) for the “Tia Maria” graphics chip found in the Atari 7800 console an unusual occurrence, and one which should be of special interest to the emulation community. They can be found alongside the rest of the Atari Museum’s 7800 information.

That such a useful document is available at all is due to a lucky find in a dumpster following the demise of Atari, when a treasure trove of documents was discarded. It seems that the existence of these schematics has been known within the Atari community for some time, and we expect before long this information will find its way into FPGA implementations of the 7800; especially since the system features nearly complete backwards compatibility with the massively successful Atari 2600.

When that happens we hope we’ll be able to bring it to you, but it’s not the first time someone’s made an Atari on an FPGA.

Via RetroRGB

Header image: Bilby [CC BY 3.0]

Entombed Secrets Partially Unearthed As Researchers Dissect Clever Maze-Generating Algorithm

If you look at enough of another developer’s code, you will eventually say, “What were you thinking, you gosh-darn lunatic?” Now, this exchange can precede the moment where you quit a company and check into a padded room, or it can be akin to calling someone a mad genius and offering them a beer. In the case of [Steven Sidley]’s 1982 game Entombed, [John Aycock] and [Tara Copplestone] found a mysterious table for generating pseudo-random mazes and wrote a whitepaper on how it all works (PDF). The table only generates solvable mazes, but if any bits are changed, the puzzles become inescapable.

The software archaeologists are currently in a labyrinth of their own, in which the exit is an explanation of the table, but the path is overgrown with decade-old vines. The programmer did not make the table himself, and its creator’s name is buried somewhere in the maze. Game cart storage was desperately limited so mazes had to be generated on-the-fly rather than crafted and stored. Entombed‘s ad-hoc method worked by assessing the previous row and generating the next based on particular criteria, with some PRNG in places to keep it fresh. To save more space, the screen was mirrored down the center which doubles the workload of the table. Someday this mysterious table’s origins may be explained but for now, it is a work of art in its own right.

Aside from a table pulled directly from the aether, this maze game leaned on pseudo-random numbers but there is room for improvement in that regard too.

Via BBC Future.

Get Coding With This Atari 2600 Development Suite

Sometimes the urge strikes to get busy coding for an old retro system, but unfortunately the bar to entry can be high. There’s a need to find a workable compiler, let alone trying to figure out how to load code onto original vintage hardware. It doesn’t have to be so hard, though. The team at [HeatSync Labs] built an Atari 2600 development station so hackerspace members can simply rock up and get to work.

With this rig, development is a multi-step process. A paper manual is on hand to provide detail of how to code for the Atari. An IBM PC is then on hand to allow the budding developer to code in assembly. This text file is then compiled into an Atari ROM, which is then passed through a special utility to convert it to an audio file. This is to allow it to be used with a Starpath Supercharger, which allows games to be loaded onto the Atari via cassette tape, or in this case, raw digital audio. By playing the audio file on the PC, connected to the Supercharger cartridge, it’s possible to run arbitrary code on the Atari 2600.

Programming in 6502 assembly isn’t the easiest mountain to climb for an absolute novice, but experienced coders will likely appreciate the no-fuss development environment. It makes for an easy gateway into the world of retro console programming, and there’s nothing like the fun of seeing your code running on original hardware.

We love a good story of retro development – like this tale of fixing a 37-year-old bug in an Apple II game. Video after the break.

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Two Joysticks Talk To FPGA Arcade Game Over A VGA Cable

We really love when hacks of previous hacks show up in the tip line. It shows how the hardware hacking community can be a feedback loop, where one hack begets the next, and so on until great things are everywhere. This hacked joystick port for an FPGA Pac Man game is a perfect example of that creative churn.

The story starts with Pano Man, a version of the venerable arcade game ported to a Pano Logic FPGA thin client by [Skip]. We covered that story when it first came out, and it caught the attention of [Tom Verbeure], particularly the bit in the GitHub readme file which suggested there might be a better way to handle the joystick connections. So [Tom] took up the challenge of using the Extended Display Identification Data (EDID) circuit in the VGA connector to support an Atari 2600 joystick. The EDID system is an I²C bus, so the job needed the right port expander. [Tom] chose the MCP23017, a 16-bit device that would have enough GPIO for dual joysticks and a few extra buttons. Having never designed a PCB before, [Tom] fell down that rabbit hole for a bit, but quickly came up with a working design, and then a better one, and then the final version. The video below shows it in action with Pano Man.

We think the creative loop between [Skip] and [Tom] was great here, and we can’t wait to see who escalates next. And it’s pretty amazing how much IO can be stuffed over two wires if you have the right tools. Check out this VGA sniffing effort to learn more about EDID and I²C.

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Racing The Beam And Dropping Some Beats

The heart of the Atari 2600 wasn’t the 6502 (or the 6507 for the pedants), it was the TIA chip. This is the chip responsible for drawing graphics on the display, racing the beam, and extremely limited support for sound generation. We haven’t seen many attempts of using the Atari 2600 for chiptunes, but that doesn’t mean it can’t be done. [John Sutley]’s Syndrum, a take on an Atari 2600 drum machine is nearly a work of art. It’s a custom cartridge for the wood-paneled Atari, and an impressive input device that turns this classic console into a beat machine

Did the Atari 2600 ever come with a drum machine cartridge? Maybe. Probably not. [John] originally built this project to experiment with the TIA chip, but found it was less tonal than a kazoo. That struck ‘Atari synthesizer’ off the list and replaced it with an ‘Atari drum machine’. There are two key parts of the build here, the first being a repurposed Asteroids cartridge that had the PROM replaced with a ZIF socket. This allows [John] to easily burn new code to an EEPROM, stuff it in the socket, and run it on the Atari. All the code was developed with batari Basic, a BASIC-inspired language that spits out .bin files for the Atari.

But running code on the Atari is just one half of this build. To do a drum machine, you somehow need to tell the Atari when to play each sound. Given the lack of expansion capabilities for the Atari, [John] turned to the controller port. The Syndrum uses Arduino Nano to bridge the DE9 controller connector to a MIDI port. Yes, it’s real MIDI, on a machine that could probably never do MIDI natively (although we’d love to see someone try).

Need a video of this mind-blowing hack in action? Here you go:

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Atari 2600 In A Game Cartridge

[PJ Evans] had a ruined game cartridge lying around, just waiting for a project. As Activision’s F-14 Tomcat game for the Atari 2600 console, it seemed ripe for use as a project enclosure of some sort. When he came across a couple of 9-pin D-sub joystick ports, he had an idea. He realized his Rasperry Pi Zero could fit inside the cartridge. Add a power button, TV color selector, difficulty switch, as well as select and reset buttons, and you have an emulator.

[PJ]’s Pi Zero had more than enough GPIO pins to accommodate all of those buttons and switches plus a bunch more for the joysticks. Why not put the emulator inside a game cartridge? In terms of software [PJ] looked into Adafruit’s Retro Gaming with Raspberry Pi resource, which has tons of suggestions for setting up game emulators. He decided on the RetroPie operating system to help him map out all of the pins, with Stella doing the actual Atari 2600 emulation.

Thanks, @seb_ly]!

Atari Now Runs Java, Thankfully Doesn’t Require Constant Updates

Java Grinder is a tool that compiles Java programs to run on platforms like microcontrollers and consoles, by outputting native assembly code and using APIs to work with custom hardware like bespoke graphics and sound chips. Amongst other hardware, Java Grinder supports the Commodore 64, which uses a variant of the 6502 CPU. [Michael Kohn] realized the Atari 2600 shares this processor, and figured he’d get started on making Java Grinder work with the Atari by expanding on the C64 work done by [Joe Davisson]. Together, they brought Java to the Atari 2600 and made a game along the way.

According to [Michael], parts of the project were easy, as some Java routines compile down into as little as 1 or 2 instructions on the 6502. Other parts were harder, like dealing with the graphics subsystem, and modifying Java Grinder to output 8-bit bytecode to fit into the Atari’s tiny 4K ROM limit. Even with this tweak, they still couldn’t fit in a game and title screen. In the end they relied on bank switching to get the job done. [Joe]’s game is pretty solid fare for the Atari 2600 — blocky graphics and bleepy sounds — and they’ve uploaded it to the page so you can try it yourself in an emulator.

At the end of the day, porting Java code to a system with 128 bytes of RAM probably isn’t going to be particularly useful. However, as a coding exercise and learning experience, there’s a lot of value here in terms of building your skills as a coder. Other such experiments have shown us Java running on other unexpected devices, like the Sega Genesis or the MSP430. Video after the break.

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