Jonathan Scobbie's SNES Romulator

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Jagasian
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Jonathan Scobbie's SNES Romulator

Post by Jagasian » Thu Jun 12, 2008 2:34 pm

Does anybody know details regarding Jonathan Scobbie's SNES romulator? Apparently he went through the trouble of creating custom circuit boards for a portable SNES project of his.
http://www.mash-mods.com/products/Mash- ... rtablesnes

One of the circuit boards allows loading SNES ROMs from an SD card onto a real SNES. It is the board labeled "SNES Romulator".

Zoigl
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Post by Zoigl » Fri Jun 13, 2008 2:46 am

wow,
it looks great <3
anyone got the schematic ? :mrgreen:

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kyuusaku
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Post by kyuusaku » Fri Jun 13, 2008 12:00 pm

Anyone could interpolate this schematic, the thing is, you need to redesign the CPLD and BIOS. The CPLD only has to:

-power on to the BIOS, register to switch to emulation RAM and unmap the following registers
-decode the emulation SRAMs, register for SRAM limiting
-decode save RAM, register to select Lo/HiROM map
-register to shift A15-A21 to A16-A22 for LoROM
-registers for SD interface

The hard part is getting SD interfacing information and writing the FAT code.

tepples
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Post by tepples » Sat Jun 14, 2008 7:18 am

kyuusaku wrote:-registers for SD interface
The SD interface could just be an 8-bit shift register that speaks SPI protocol. Or you could use CompactFlash and make an ATA interface instead.
The hard part is getting SD interfacing information and writing the FAT code.
I wonder if the source code for various SD reader drivers in DLDI might help.

PDP-13
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Post by PDP-13 » Mon Jun 23, 2008 7:31 pm

I've actually seen a self contained 'FAT on a Chip' card, it does all the legwork of reading / writing a FAT file system with a MC.

Just uses some simple 'COPY, LOAD, DIR' type commands...

Forget the name however. It was expensive.

AVR's are what $5 these days? shesh.

cybertron
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Post by cybertron » Sat Sep 20, 2008 9:13 pm

Hey guys, I'm the one who did this project and was very surprised to see my name on this forum!

kyuusaku: you got it down pretty much exactly. The only detail missing is the 4MB of RAM is on a separate bus (since its 3.3v). You are right about the schematic, its trivial compared to the CPLD and menu program.

The CPLD acts in between the SNES and the RAM, allowing it to take over and write directly to the RAM while the menu program is running from flash. This is the only way to load games without being unbearably slow. Now it takes just a few seconds.

SD interface is really simple, although it was difficult to find the datasheet for. Its basically an 8 bit shift register, with software sending commands and receiving data.

Writing the menu program in assembly was a pain, so there is no FAT filesystem at all. I put all the ROMs in one huge file with list data in front of it.

The whole thing was wayyy too much work :(

Any other questions about this?

We will be releasing a new product on MashMods soon, a SNES FLASH CART and a nice USB programmer/reader to go with it.

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MottZilla
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Post by MottZilla » Sun Sep 21, 2008 10:12 am

Will you please post a topic here when your new SNES Flash cart goes on sale? I'm sure we'd all like to know when it becomes available.

Any chance you'll ever make a SNES cartridge that loads ROMs from a CF Flash or SD memory card similar to your SNES Romulator?

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Post by byuu » Sun Sep 21, 2008 5:42 pm

Any chance you'll ever make a SNES cartridge that loads ROMs from a CF Flash or SD memory card similar to your SNES Romulator?
Yes, precisely. Much, much more valuable to have a cart that takes memory cards, rather than requiring custom USB flashing software (which probably only works on older copies of Windows.)

I'd be very interested in picking one up as well, assuming it is reasonably priced [~$50-120 or so]. Always looking to expand my available options for running code on real hardware.

So far, I have two copiers and an awesome controller <> serial interface + SRAM cart from blargg. A memory-card flash cart would be great for the latter ... could make a much larger boot ROM with lots of fancy options, and no risk of SRAM loss when yanking the cart out while its running (only a ~0.1% chance now thanks to a 10-frame x ~100 DMA loop.)

Would also be nice if someone sold RGB modded SNES units that can stream that data to a PC for analysis (eg to work on a pixel-level PPU emulator), but I'll keep dreaming ;)

cybertron
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Post by cybertron » Sun Sep 21, 2008 6:52 pm

I thought about making one that uses an SD card but concluded that the RAM and extra chips would not fit in the cartridge (unless I used BGA or something crazy).

The USB programmer is really nice, and will work on any version of windows (uses an FTDI chip). Plus you can back up regular carts and their save RAM, or copy a save from an emulator to the real cart.

With a flash cartridge you get an authentic retro experience :) Only one game means you will actually play it, versus 700 you will never play. You could use it for hacks of fullsize games, or translations.

I haven't determined a final price, but it will be affordable. I will defiantly post a thread when its done (just have to figure out mass producing).

Whats this about BIOSes and DMA?

tepples
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Post by tepples » Mon Sep 22, 2008 6:12 am

cybertron wrote:I thought about making one that uses an SD card but concluded that the RAM and extra chips would not fit in the cartridge (unless I used BGA or something crazy).
Look at the CycloDS miniSD for Game Boy Advance, and see how the chips manage to fit in the cart.
The USB programmer is really nice, and will work on any version of windows (uses an FTDI chip).
Does it use a non-generic kernel-level driver? If so, it won't work with 64-bit Windows Vista or later unless the publisher of the driver buys a $200/year code signing certificate. That's cost-prohibitive unless you're mass-producing the hardware that goes with it.

byuu
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Post by byuu » Mon Sep 22, 2008 11:39 am

The USB programmer is really nice, and will work on any version of windows (uses an FTDI chip).
Great, except my main PC runs Linux; and my secondary runs OS X. Good for ~92% of people, at least.
Whats this about BIOSes and DMA?
Sorry, I was explaining what I'd use it for (reverse engineering); though I'm well aware I'm quite outside of the norm there.

Ah well. As it stands, it sounds like a good product; but it doesn't offer anything Tototek hasn't already with their Super Flash Cart. But since they're out of stock anyway, and because we can never have too much homebrew stuff, it still has plenty of merit.

Best wishes with the product!

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MottZilla
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Post by MottZilla » Mon Sep 22, 2008 1:47 pm

Tepples, the DS devices stream the data off the SD card. The SNES requires it be loaded into RAM first to be fast enough, so that must be what he means.

cybertron, if the RAM and extra chips wouldn't fit in a normal cartridge, why not just make the cartridge bigger? Backup devices say on the top of the SNES and were pretty big, no one seemed to mind that. Infact I think it looks cool. So you could certainly just make the cartridge taller or make something in the shape of a backup unit.

As byuu was saying, a SNES cartridge that loaded ROMs off SD or CF cards would be totally awesome. While I can see your point of people having a million roms on a card they never play and such, the idea has already been tested in the NES with the PowerPAK and the result was pure awesomeness. Such a product for SNES would be equally if not even more awesome. So you might want to consider the idea again.

I do agree with byuu though that your Flash Cart will be very welcomed. While the NES is great and all, I think the SNES needs more loving. More products like this are a good thing.

tepples
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Post by tepples » Mon Sep 22, 2008 5:42 pm

MottZilla wrote:
tepples wrote:Look at the CycloDS miniSD for Game Boy Advance
Tepples, the DS devices stream the data off the SD card.
What DS devices? I'm talking about devices that are compatible with software for the Game Boy Advance platform. Like NES, Game Boy, Super NES, and N64 Game Paks, GBA Game Paks have a word-addressed ROM. The GBA adapters that take SD cards copy up to 32 MB from the SD card into a RAM on the adapter, just like PowerPak copies games from the CF to its RAM. CycloDS miniSD is one of these; others include SuperCard and M3. Are you thinking of SLOT-1 adapters such as R4, SuperCard DS One, M3 Real, and CycloDS Evolution, which use a block-addressed microSD card to simulate the block-addressed ROM of a DS Game Card?

cybertron
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Post by cybertron » Mon Sep 22, 2008 9:17 pm

I checked Digikey and I can get 1Mx16 SRAM chips. So basically 2 chips instead of one flash. Plus a huge CPLD to take care of all the bus stuff. So basically I probably could fit it in a normal cartridge. It would still take a while to design, but could possibly be my next project.

I checked the FTDI website, and it looks like they do have drivers for Vista x64, and linux. I love FTDI chips, they are so easy to use. It even has the oscillator built in so there are no external components.

Tototek has the advantage of more then one game, but I think USB makes mine more accessible. Modern computers don't have parallel ports (that work).

Right now im taking apart old sports games to steal their CIC and case. Bunnyboy made his own cases, and uses Kevtris's Ciclone. I don't know how many games I can find to take apart :(

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kyuusaku
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Post by kyuusaku » Mon Sep 22, 2008 11:13 pm

I think you should consider DRAM instead of SRAM; SRAM at that density not only is way expensive but is IMO completely wasted on a SNES device.

(Unless you're talking about SRAM because you're thinking of replacing your cart's flash with SRAM, which wouldn't make any sense!)

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