Author Topic: Mega Everdrive FPGA  (Read 11181 times)

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Offline Jpg3D

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Mega Everdrive FPGA
« on: August 06, 2014, 07:26 PM »
Hi, i just registered here for asking you something.

In the MegaEverdrive's manual i can find this affirmation:
"Homebrew software can load it's own customizd firmware into the FPGA"

but I can't find any information about how i can load my firmware to the fpga.
¿How can be this be achieved? Im really interested on that.
« Last Edit: August 07, 2014, 11:28 AM by Jpg3D »

Offline KRIKzz

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Re: Mega Everdrive FPGA
« Reply #1 on: August 07, 2014, 02:20 PM »
This is really possible, but unfortunatelly i don't have any instructions or samples at this moment

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #2 on: August 07, 2014, 03:14 PM »
My idea is to develop something similar to SVP. Draw polygonal images that could be transferred by DMA to the vdp like virtua racing.  Im pretty sure that cyclone 2 can draw much more polygons than SVP so i want to try to develop something much better. The ideal thing will be with somekind of texture mapping, but i dont know if this is a good idea because of the color limitations.

i took a look to the Mega Evedrive circuit, and i suspect that this can be achieved, i just have some questions.

whats the %free of the fpga for our custom circuits?
Can the fpga share memory with the mc68000 and the vdp so this memory can be transferred using DMA?

Thanks for the last answer.

Offline KRIKzz

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Re: Mega Everdrive FPGA
« Reply #3 on: August 07, 2014, 05:47 PM »
System functions take around 33% of fpga, but your code can use whole fpga. Anyway you will need to unload system code before than load yours own.
I not sure what you mean when you say "share memory with the mc68000 and the vdp", but DMA can be used

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #4 on: August 07, 2014, 09:37 PM »
I was trying to ask if same memory bytes than mc68000 uses for load data and execute program, can be accessed by the fpga too. Maybe i had not explaned myself. i lack in english sometimes.

So by this way the fpga could draw polygons while mc68000 is woking, and i could access the memory filled by the fpga by just using "move" instructions. So i can control this custom pheripheral with few instructions.

anyway, using dma would be enought for this purpose.
Thanks for answering!

At the moment i'm just coding some basic tests so i can see my programs working. Some sprites, random images on the screen. Just for getting some experience programming on this system before i start with my project.
« Last Edit: August 07, 2014, 09:44 PM by Jpg3D »

Offline Chilly Willy

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Re: Mega Everdrive FPGA
« Reply #5 on: August 07, 2014, 09:57 PM »
I think what he wants to do is have the FPGA act as a texture mapping engine. It would walk the raster lines of the poly (say, a triangle), and then read the texture out of the MD rom or ram, and store it to the memory in the MED.

One thing to remember - the rom in the MD while using the MED is actually ram in the MED. So being able to access a texture in rom is really just asking to be able to use the MED ram as the texture source for the rasterizer. Just design the texture mapping to read from the MED ram and store to the MED ram. You can't make your own DMA to vram inside the MD, so you'll need to use the VDP DMA for transferring the data from wherever into the vram. Remember that the MED ram is the rom as far as the MD is concerned, so using the VDP DMA to load the mapper destination bitmap from the MED ram is exactly the same as DMAing from rom.

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #6 on: August 07, 2014, 10:15 PM »
i know that i have to use the vdp dma to show the final image on the screen. And this step can not be skipped.

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #7 on: August 14, 2014, 01:48 AM »
I'm not pretty sure if the idea you explained is the same i have got.

My idea is as you said, to use the FPGA for drawing a polygonal image into MegaEverdrive RAM . After this, Enable VDP's ram to fill  video memory with this image, so i can display poligonal graphics on the screen.

You made me comprehend that the FPGA can access the RAM that mc68000 read for play roms. So reached this point, this project completely possible to do. Am i right?

Offline KRIKzz

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Re: Mega Everdrive FPGA
« Reply #8 on: August 14, 2014, 04:17 AM »
FPGA can render image to ROM memory and then you can transfer image to VDP via DMA. So, yes, it is possible. I already play a bit with some rendering function on mega ED. I used it for fast rendering of doom-like graphics and image transformations

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #9 on: August 14, 2014, 11:44 AM »
i'm very impatient for doing this. When will we be able to download any kind of documentation/examples/guide and start toying with the fpga?

Offline KRIKzz

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Re: Mega Everdrive FPGA
« Reply #10 on: August 14, 2014, 04:37 PM »
at this moment i very busy with ed64-v3, probably after that i will take care about docs and samples for mega

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #11 on: August 14, 2014, 04:54 PM »
ok! really thanks for the answer. i ll be waiting impatiently.

Offline leosmendes

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Re: Mega Everdrive FPGA
« Reply #12 on: August 20, 2014, 01:34 AM »
hello everyone, hope I'm not asking silly, but it would be possible "sega 32x" in fpga in a "everdrive cartridge" or other system like nes ???

Offline tertu

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Re: Mega Everdrive FPGA
« Reply #13 on: August 20, 2014, 11:11 PM »
A 32X wouldn't be possible in either the Everdrive MD or Mega Everdrive because it needs hardware (for video and synchronization) that isn't in those cartridges, even if there is enough space on the FPGA and in RAM to accommodate it. Other consoles may be possible depending on the size of the FPGA, but it's a lot of work that probably wouldn't be done by anyone for a long time.

Offline Jpg3D

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Re: Mega Everdrive FPGA
« Reply #14 on: August 30, 2014, 01:32 PM »
I think it's nearly imposible. The fpga has his own cpu that possibly could emulate 32x but 32X has a video output that you should add to the cartidge, you would need to wire the fpga to that output, and i'm not sure if there are enought free pins do do it. Unless you fix this, you are limited to MegaDrive color palete.

I would not counting with that to going to happen.