The HappyCart is an Atari VCS (aka 2600) cartridge emulator with bankswitching support for 2KB-16KB cartridges. This allows ROM images of Atari cartridges to be played on real VCS hardware, with real Atari joysticks, sitting on your butt in front of a real television like nature intended. There’s no better way to recapture those hours of lost youth, and aggravate old repetitive stress injuries!
The basic premise is that a static RAM (SRAM) chip can be used to hold program content for the VCS to execute, just as a ROM or EPROM device would in a real cartridge. By adding an “out-of-band” method of loading code into the SRAM chip, different games images can be uploaded and then played on real VCS hardware. As this project was done in the days before USB was widely deployed, game data is uploaded to the HappyCart is via a PC parallel port.
The initial hardware design was a collaborative effort with Mike Andrews, and it went through three iterations. The first version was hastily hand-wired, and ultimately scrapped before it was ever fully debugged. The second version was based on an 8255 GPIO board built for another project, and hand-wired to a modified Atari cartridge containing a SRAM chip. The third version was rebuilt from scratch to fit inside of a cartridge, but was otherwise very similar to the second version in terms of operation and capability.
I designed the fourth generation hardware on a custom printed circuit board that fit inside of a modified Activision cartridge. It is the first version to support bankswitching modes for larger cartridge support (2KB to 16KB), as well as providing SuperChip and RamPlus emulation. The bankswitching logic is implemented using Xilinx CPLD chips, with code written in VHDL. Like previous generations, it connects to a parallel port of a PC, and Windows software provides game database with a unique documentation and cartridge image browser feature. This software, called HappyExplorer, can download ROM images to the HappyCart attached to the PC or launch an emulator.
If you’re interested in learning how it works, I’ve released some of the design as open source under the Mozilla Public License 2.0. Check it out on GitHub!
Click to read a funny email about HappyCart from 1999
We used to get all kinds of crazy emails about HappyCart back in the day. The email below is one of the funniest, even attracting the attention of some folks on Atari Age back in 2002.
Date: Fri, 28 May 1999 03:08:32 -0500 Subject: [address removed]requestinforonHappykart for atari 2600vcs video game cartidge Yes I wanted to ask You a favor. My Name is [name removed] and I am having a bit of a problem to get certain video games cartidges called Prototypes video game cartidges. What I have done is I have gotten some of The screenshots of The Original Images from The Actual video game Pictures stills of The rom Images. Now they are only still pictures like Monster cise, Peek a boo Good Luck charlie brown, certain Titles That I do have The screen Images. I was wondering When Are You going to Release The Happycart? Will it be release This fall? Or comming Later in The fall in October 1999. You see I do have some of The Screenshots but I donot have all of The Screenshot for The atari 2600 vcs. If You going to release The Happycart I would like to purchase The Happycart. I do have The Still Image of The video games. I need You to email Me if You want Me to make a copy and provide a copy of The original title. I will help You out if You want to goahead and email Me as fast as quickly as possible. Also if You do get The 2600 happycart working can You goahead and atleast try to get The Happycart release. You see I AM Having a hard time in finding these Prototypes video games cartidges like tempest,Cloak and dagger,Save Mary,monster cise andpeek a boo and miss piggys wedding,good luck charliebrown. The Only ones I wasnot able to get is I was not able to get cloak and dagger and Turbo,put out by coleco for atari 2600. Zookeeper and swordquest airworld AND ALSO LADYBUG FOR THE ATARI2600. WITH WHITEWATER MADNESS. I AM JUST SORRY THAT I COULDNOT GET A PICTURE OF THESE VIDEO GAMES. I HOPE YOU ARE COMMING OUT WITH THIS 2600 HAPPYCART AND I HOPE IT IS COMPATIBLE WITH THE ATARI 2600 VCS. IS THE HAPPYCART COMPATIBLE WITH THE ATARI 2600 UNIT? How do You hook it Up to The Computer to The computermodem? How will it work? Will it work 100% with no defects? Will The system work 100%? WILL THE 2600 HAPPYCART BE ABSOLUTELY FOOLPROOF WITH NO TECHNICAL PROBLEM? If You market This Happycart I will support The Happycart if You show Me how it works and How do You Hook The Happycart from The Modem to The atari 2600? I Would also need instructions how to work The video game of The Happycart? I would need to Know how to attach each attachments to The 2600. Do You hookup The Modem from The computer to The Happycart in order to do this I would need instructions in how to hookup everything where There should also be a garunteed That The Happycart willnot shut My Computer down where it willnot erase The data. I would have to be garunteed That The video game cartidge of The Happycart will work 100% with no defects and it willnot shutdown My atari 2600 vcs Unit. Until I see Until I get proof of That The Happycart will work. I would have to see somekind of Demonstration. I would have to find out That I Would have to see somekind of videotape showing That The Happycart will work. I would have to have somekind of garunteed of a live demonstration on Showing How The Happycart works and how do You hookit Up to The 2600? If You need the images I can send them to You The ones that I do have. I would have to make a copy and send to You. I need Your complete name address,citystate and zipcode and a Phone Number to contact You. In fact everyonce of a while there are special convention being held in Dallas,TX SOMETIMES THERE ARE COMPUTERS AND SOFTWARE CONVENTION BEING HELD IN DALLAS. BUT IF YOU HAVE THE ITEMS INSTOCK PLEASE GET THE HAPPYCART RELEASE SOON. BECAUSE I HAVE BEEN WAITING FOR SOMETHING LIKE THIS TO COME ALONG. WHAT I WANTED TO SEE IS A SEPERATE FOUR VERSION MULTICART LIKE A CARTIDGE THAT FITS LIKE VOLUME ONE ATARI PROTOTYPES VOLUME 2 PARKER BROTHERS UNRELEASE VERSIONS CIRCUS CHARLIE,THE INCREDIBLEHULK MC.DONALDS TWO VIDEO GAME FORMATS, THE LORD OF THE RINGS JOURNEY TO RIVENDELL,STARWARS EWOKS ADVENTURE THE COLECO TITLES FOR ATARI 2600 OR RELEASE THESE ALL OF THESE TITLES IN ONE VIDEO GAME CARTIDGE OF THE HAPPYCART. YOU CAN EMAIL ME AT [email address removed] REQUEST INFOR ON THE happykart atari 2600. I Have been waiting for someone to come out with a completed video game of The Happykart. Please contact Me as fast as quickly as Possible. I sure do Thank You very very much. If You do come out with This Product it may Help very very much. I hope You come out with it either in Sept or Oct Pretty soon. I just cannot wait. If it works 100% I will be very very interesting in Purchasing The Happykart. Please respond as fast as quickly as possible.