Has there ever been an open source version of a CV SD Cart?

[+mytek]

I know about the AtariMax Ultimate SD Cart already, and that does look like a nice solution. But it's perhaps more than is needed to simply load the virtual ROMs off an SD card into the ColecoVision, and the price tag is a bit steep. So I'm wondering if anyone other than AtariMax rolled their own, and were kind enough to make it open source?

 

Not really looking for one that already has a PCB layout included, mostly just interested in a schematic and the firmware to flash into the inevitable MCU or FPGA.

[rietveld]

http://zx81.zx81.free.fr/serendipity/index.php?/archives/522-ColecoVision-63-in-1-Flash-Cartridge.html

 

 

[NIAD]

No SD Card solutions like you are looking for, only the available for purchase AtariMax and BackBit SD carts.

 

Also, the MultiCart that rietveld linked and IIRC one other project only support up to 32K carts and are a locked design… the games you want are burnt to EPROM/Prom.

Edited September 7, 2022 by NIAD

[Captain Cozmos]

Last year mine blew up when I turned ADAM on.
I emailed Steve, I believe his name is, he said send it back...boo hoo I forgot.

I would like to know if anyone else had this issue as if it's just a blown fuse so I can fix it myself.

[+mytek]

On 9/6/2022 at 9:21 PM, NIAD said:

No SD Card solutions like you are looking for, only the available for purchase AtariMax and BackBit SD carts.

 

Also, the MultiCart that rietveld linked and IIRC one other project only support up to 32K carts and are a locked design… the games you want are burnt to EPROM/Prom.

Yeah I was afraid that would be the case. There was a guy back in 2013 that was attempting to do this with an ATMEGA32 chip and some SRAM. If I recall correctly I think the plan was to extract CV ROM files from a FAT32 formatted SD card - move the file to the SRAM - and then run that as if it were a ROM cart. Unfortunately he dropped off the map before completing it.

 

Edit: I should probably mention why I was looking for this. I'm the creator of the Atari 576NUC+ system (an extremely sized reduced version of the XEGS). Anyway in reference to that system, it was designed to accept a daughter board for I/O expansion (SDrive and FujiNet), and I was thinking that a Colecovision daughter board would be pretty cool.  However just like the Atari aspect on the 576NUC+, an SD Card for getting the CV games into the system is needed.

 

The CV daughter board would be a nearly complete version of a full sized system, minus the cartridge and expansion ports, and likely even the controller ports, which would get handled via the PS/2 keyboard through emulation by the arrow keys. Edit: I've reconsidered and will probably share the 576NUC+'s joystick port connectors, since they match what a CV used.

 

I know... pretty crazy idea.

Edited September 11, 2022 by mytek
Retaining standard joystick ports

[+mytek]

Well if you can't find an Open Source version, I guess you gotta roll your own. Here's my start with doing just that.

This is part of a bigger project I'm working on, but it is at the heart of getting games from an SD Card into the CV daughter board. Of course I've still got a long road ahead in creating the firmware to make this all work.

 

So the basic idea is to have game ROM files saved in FAT32 format on a SD Card (via whatever PC you like to use). The PIC chip will get a directory of that card, and create a list on screen (somehow???). Using the joystick in port 1 Using 576NUC+'s PS/2 keyboard's ARROW keys, the list can be scrolled through UP & DOWN, with the ENTER key trigger button making the selection. At that point the PIC removes the 32Kx8 SRAM from the CV bus, reads the SD Card ROM file, transferring it a byte at a time to the SRAM. When it's done, control is passed back to the CV, and either a Reset or a Power Cycle is performed to load the game (I'm not sure what is required - obviously I need to maintain power to the SRAM during the power cycle so it doesn't lose its data).

 

I have a real Colecovision on the way from eBay, which will serve as my initial test bed. And I obviously have much to learn about how the CV actually works, so this will likely take awhile

Edited September 11, 2022 by mytek
Updated Schematic and Functionality

[+mytek]

I've decided to not continue down this path. It'll never be as good as it should be, and simply doesn't compare with the AtariMax Ultimate SD Cart. However it was fun and interesting, and made for a good mental exercise. This was going to be a part of another project, but I've made the decision to just go with a standard cart port.