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Color Computer Blank Cartridge boards...

Al Hartman

Veteran Member
Joined
Aug 13, 2013
Messages
912
Location
Keansburg, New Jersey, United States
What's really needed in the Color Computer world is a new supplier of blank ROM cartridge boards for housing up to a 16k EPROM.

Here's a schematic for one: http://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/coco/coco_tm_37.png

(from this page: http://www.bighole.nl/pub/mirror/homepage.ntlworld.com/kryten_droid/coco/coco_tm_s3.htm )

These would be useful for mounting a Drivewire ROM into (similar to the Serial Port Booting on the Universal XT-IDE BIOS).

http://sites.google.com/site/drivewire4/


I've seen projects for the Atari 2600, 8-bit, Colecovision, and others..

I'd buy a bunch of boards...
 
I know of one PCB supplier catering to hobbyists who offers ENIG surface finish (that is, gold plating): http://oshpark.com/

So if somebody is thinking of making CoCo cartridge PCBs, I'd suggest manufacturing through OSH Park so we get gold plated edge fingers.

Now, what would be preferable: a bare card that accepts old 27xxx EPROMs, or an assembled one that uses a modern flash chip and provides some way to reprogram it without needing an EPROM programmer?
 
Now, what would be preferable: a bare card that accepts old 27xxx EPROMs, or an assembled one that uses a modern flash chip and provides some way to reprogram it without needing an EPROM programmer?

I'd like to see both, as I have a lot of EPROMS here that need a home. But something like Drivewire would live better in a reprogrammable EEPROM as that software might change. ADOS would be another, but that needs to be in a disk controller.
 
Slap an FPGA on the board with suitable interface electronics, and then it can be a reloadable Program Pak and/or a disk controller and/or an RS-232 interface and/or a drive emulator and/or whatever else. I'd use a Xilinx Spartan 6, some level translators for interfacing to 5V stuff, an STM32F series microcontroller to load up the FPGA and do other useful functions, and a MicroSD card for the microcontroller to boot from and load FPGA configurations from. It's one of those things I daydream about but am unlikely to ever find the gumption to start, let alone finish. Maybe somebody else will make it for us?
 
How about a cartridge board that can be assembled either with a socket for a standard EPROM, or with an SRAM with a write-protect switch and either a coin cell or supercap to back it up? In the latter configuration, you would program the memory by simply writing to the ROM address space, such as with CLOADM or some utility program. Flip the write-protect switch, and it'll act like a ROM, but no special programming hardware is needed. A second switch can disconnect the signal that makes ROM cartridges auto-boot, and that could be useful in either the EPROM or SRAM configurations.

A similar feature could be implemented with one of Maxim's EPROM-pin-compatible battery-backed SRAM chips, but I don't like the way that the backup battery is integrated into the SRAM package and is not separately replaceable.

Come to think of it, it wouldn't even be necessary to make the EPROM socket vs. battery-backed SRAM mutually-exclusive assembly options. An SPDT switch could determine whether the EPROM socket or SRAM chip gets the chip select signal, so they could both be installed simultaneously.

If the SRAM was larger than needed, then it would also be possible to have a switch to select different banks of the SRAM, thus giving multiple ROM images on one cartridge with a switch to select them.

The FPGA board would be lots of feature-creep as you have pointed out, but adding a simple battery-backed SRAM to an EPROM board might be just right for folks who don't have an EPROM programmer.

Does it need to come with a plastic box? Or can it just be made so that it would fit in a standard Program Pak box with holes cut in the edge for switches, and let folks roll their own boxes if they wish to?
 
Cloud9 is doing a fancy reprogrammable cartridge. It should be out soon. All I wanted help with was a little PC board that would take up to a 16k Eprom that could be used to put a program into the cartridge space. I even have a cartridge that can be examined and copied.

I'll try to do it myself if I can't find anyone to help me. But, since I know bupkis about this stuff, I'm probably going to end up wasting money on prototype boards that don't work.
 
I've been stuck at home for the last few days with a cold. Today I was able to think again (so I should be back to work tomorrow), so I killed time playing with a Program Pak design. It's still a work in progress, but here's a pic of what I have so far. It should support 2732, 2764 or 27128 EPROMs, and the auto-boot function is controlled by a jumper. If I measured that crusty old Color Scripsit cartridge correctly, it should fit in an original Program Pak plastic housing.

I haven't looked into the price yet. My first impulse would be to make it through oshpark.com for gold plated fingers.

Cart.jpg

What do you think?
 
Ok, I think it's done. Would anybody care to review this before I send off for some prototypes?

Top side:
Top.jpg

Bottom side (viewed through board):
Bottom.jpg

Schematic diagram (hosted at GitHub; 260k PDF too large to attach):
CoCoEPROMpak_v1.0.pdf
 
Regarding pricing and so forth:

I don't expect to make money on this particular project, and I don't think it's "sexy" enough for me to mark it up enough to even make enough to cover the time I'd spend handling order fulfillment. But have no fear... I plan to use this project as an excuse to try out a small-run PCB fab called OSHpark, particularly because they offer ENIG (gold plating) which is nice for card edge fingers. They also happen to have a service called "Shared Projects" that looks ideal for this sort of thing, in which I'd like to just give away the design and let anybody order up PCBs based on it. If I understand it right, once I'm satisfied that my widget works, I can make it available for anybody to order it from their site at the normal cost. For example:


Here's their current pricing:


This board is 2.1" x 1.75" = 3.675 square inches, so it looks like a batch of three bare boards would cost $18.38, or $6.13 each. I think that's pretty cheap! Also, they will be purple.

So what I propose to do is this: I'll order up a batch of boards for me to verify that the thing works. Once I'm satisfied with it, I'll put it up in the Shared Projects area and share the permalink so anybody can order it. You would need to order in multiples of 3 boards, they would cost about $6.13 each, and I wouldn't need to lift a finger. How does that sound?

BTW, I've noticed DriveWire cables and HDB-DOS ROMs on eBay. If some enterprising person decided to use my boards to sell HDB-DOS cartridges on eBay, that's fine with me. I'm releasing the board design under the GPLv3 license.
 
Nice!
Would be nice to add a jumper to switch between two 16K banks when using a 27256 EPROM?
Should be simple enough to implement and would allow dual roms on one chip!
 
Simple meant no flash chip. But, putting a bank select switch in sounds like a good idea.

I could have one Drivewire Cartridge with the Coco 2 and Coco 3 ROMS burned into it, and be able to switch between them. Then, I wouldn't need two cartridges.
 
Somebody else will need to make the case. Any volunteers?

P.S.: This board is intended to fit in a regular Program Pak cartridge, based on my measurements of an old Color Scripsit housing.
 
I would be interested in one of these. I have some 27C64's and 27C128's I bought a few months ago that I would really like to use to put the DW3 CoCo2 and DW3 CoCo3 ROM images into. Plus if there is a jumper bank would be easy to add a switch to the back of the cart pack and run the wires to the jumper block on the board so that way I can easily switch between the images stored in the ROM. :D
 
I would be interested in one of these. I have some 27C64's and 27C128's I bought a few months ago that I would really like to use to put the DW3 CoCo2 and DW3 CoCo3 ROM images into. Plus if there is a jumper bank would be easy to add a switch to the back of the cart pack and run the wires to the jumper block on the board so that way I can easily switch between the images stored in the ROM. :D

EXACTLY why I thought these would be a great idea!
 
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