ROM board with a tiny DMA engine

Fessor · 17:10, 18 January 20

How does it work? Does it transfer only from ROM to RAM or can it also transfer Bytes within the first 64kb of RAM?

hlide · 14:42, 03 October 20

Digging up an old topic because I'm fully interested in that project: any progress? any links to source which to build one?

Quote from: doragasu on 07:56, 14 February 17

doragasu · 18:06, 03 October 20

The cart is 100% working, including DMA functions. Unfortunately it seems development of the two games that were considering using it is halted, and no more devs have shown interest on it, so it is collecting dust in a drawer.
I usually open source my designs after a game has been released for them, but if there is interest, I might consider open sourcing this without waiting anymore, since maybe that is better than having it growing a thicker dust layer.

TotO · 01:52, 04 October 20

Well said! I'm pretty sure that new games/tools projects can use it w/o waiting.

zhulien · 11:03, 04 October 20

The way I see it, the M4 does DMA into ROM space. Because you are making a ROMBoard, you can very well do DMA to ROM space also. In fact, even if you make an external RAM, you can DMA to that external RAM too - just the CTRC for example cannot display directly from that external RAM - but you could enhance a CPC a lot with such DMA - such as super fast vector graphics maths in RAM, super fast new instructions to do memory transformations (almost instantly from a Z80 point of view).

GUNHED · 19:25, 04 October 20

Hi!

Somehow I think most of us missed that the card is finished and working now. It would be great if you open a new topic, something like "XXX release" and explain the working card in the first post. Also please tell us where to buy it and how much it would cost.

I'm very interested in supporting the card with my software, but it's kind of hard to read through all this posts.

In this forum lots of posts get published, it's easy to miss the important stuff (like this great expansion) between all the other things.

Quote from: doragasu on 18:06, 03 October 20
The cart is 100% working, including DMA functions. Unfortunately it seems development of the two games that were considering using it is halted, and no more devs have shown interest on it, so it is collecting dust in a drawer.
I usually open source my designs after a game has been released for them, but if there is interest, I might consider open sourcing this without waiting anymore, since maybe that is better than having it growing a thicker dust layer.

doragasu · 08:47, 10 October 20

That's a great idea. Currently you cannot buy it. I am pretty busy and I have not produced the carts. When I release the schematics and sources, if anyone is interested in producing it, there is no problem. If no one wants to produce it, but it gains enough interest to send a batch to the assembly line, I can do the work.
But first I need some time to seat and release everything properly.

Ygdrazil · 06:31, 11 October 20

Hi doragasu
Very insteressting project...
I must have missed this project first time around!
How does it work?
What CPLD is used and can the CPLD be reprogrammed from the CPC or is a special device needed for (re)programming the CPLD?
My knowledge of CPLD's are minimal

Please do release the documentation...

Regards,Ygdrazil

Quote from: doragasu on 08:47, 10 October 20That's a great idea. Currently you cannot buy it. I am pretty busy and I have not produced the carts. When I release the schematics and sources, if anyone is interested in producing it, there is no problem. If no one wants to produce it, but it gains enough interest to send a batch to the assembly line, I can do the work.
But first I need some time to seat and release everything properly.

GUNHED · 13:07, 11 October 20

Quote from: doragasu on 08:47, 10 October 20
That's a great idea. Currently you cannot buy it. I am pretty busy and I have not produced the carts. When I release the schematics and sources, if anyone is interested in producing it, there is no problem. If no one wants to produce it, but it gains enough interest to send a batch to the assembly line, I can do the work.
But first I need some time to seat and release everything properly.

In this community we have some specialists in making PCBs for the CPC. Would be great if they can help.

I would love to buy two cards. If anybody else is interested please post here, so we can assess how big a first batch of this great project should be.

doragasu · 19:18, 12 October 20

The CPLD is a LAMXO256C from Lattice. To program it, you need a programmer, but building one is very cheap, you can use any FT2232 board like this: https://www.aliexpress.com/item/32961246303.html
I built one using that board and designed and 3D printed a case:

To write ROMs into the cart, you need a programmer. I have also designed. It is very simple and it just has a single microcontroller chip and a bunch of passives. Here you can see the programmer with the cart attached:

The cart case in the photo is one I designed, 3D printed in ABS, then did a treatment using acetone steam to smooth the surface. Some more photos:

GUNHED · 20:46, 12 October 20

An MX4 version would be great, or a version with drive through expansion port.

doragasu · 20:14, 18 October 20

The PCB has been designed with dual connector, so you can mount a DIL connector and plug it into an MX4. And as you can see, the programmer has also the connector, so you can program carts with the MX4 format. What I have not done is designing a 3D printable cartridge case using the MX4 format.

GUNHED · 21:23, 19 October 20

Great, now I just need to wait until I can get a ready-to-be-used card.

hlide · 11:23, 24 October 20

Open sourcing it would be great. I'm curious about how you deal with the GA restrictions. It would be a shame that all your work will end in a bin.

roudoudou · 12:22, 24 October 20

@Duke could an M4 board do DMA with an internal software upgrade?

Duke · 08:13, 25 October 20

Quote from: roudoudou on 12:22, 24 October 20
@Duke could an M4 board do DMA with an internal software upgrade?

Maybe possible, however it would probably be at the cost of some other feature, like rom/cart emu/hack menu at runtime.

GUNHED · 18:23, 25 October 20

Quote from: roudoudou on 12:22, 24 October 20
@Duke could an M4 board do DMA with an internal software upgrade?

What would the gain?

DMA is great for RAM, but not for ROM - well, except Cartridges maybe.

roudoudou · 18:29, 25 October 20

Quote from: GUNHED on 18:23, 25 October 20
What would the gain?

have DMAs with the M4 card

GUNHED · 18:33, 25 October 20

doragasu · 18:13, 08 December 20

Well, it took a lot of time, but finally I had a slot to sit down and open source the project. You can find everything (schematics, sources, HDL, case CAD files) here:
https://gitlab.com/doragasu/romba
Currently documentation is scarce, but I plan to add at least some more README.md files for each subproject. Again, when I get the time, so no promises about the schedule.

TotO · 18:57, 08 December 20

Great!

Now, with this kind of free project, it is IMHO better to not offer the gerber files to avoid eBay peoples making money on your back by only selling PCB to the final users without any support. The technical content to provide your knowledge is far enough. Thank you!!!

doragasu · 21:16, 08 December 20

Well, let's say I was not planning to become a millionaire with this

GUNHED · 23:05, 08 December 20

Hi, reading the internet documentation this thing is super amazing!!!

Will there be somebody who can built them and sell me one?

Since I'm more a software person I would like to support it with FutureOS (and future games) too.

TotO · 23:17, 08 December 20

Quote from: doragasu on 21:16, 08 December 20
Well, let's say I was not planning to become a millionaire with this

Obviously... $:-\$

doragasu · 22:25, 11 December 20

I have added more README.md files in each software/firmware subproject, and updated the main one. Find it in the Gitlab repo:
https://gitlab.com/doragasu/romba/
I have added almost all the documentation I wanted, excepting the registers mapping info and a brief description about how to use them.

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ROM board with a tiny DMA engine