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#11
Re: flashcart for sale??
Posted on: 2006/6/18 17:45
Nintendoid!
Joined 2004/10/25
USA
100 Posts
CoderLong Time User (15 Years) App Coder
So, I to have been working on an in console flash cart for ever. But alass I get 3/4 of the way through the design and run out of time. Lameboy has it right. You need a flash cart that is programed form code loaded in to ram by a boot loader that connects to the pc via the link cable. We know how to do everything but do an in game flash of the rom cart. I think if you put some flipflops at a specific address in expantion ram you could initiate the activation of /WE by writing to a specific address. Unfortionently the flash requires several writes to program a single byte, the question is, will noise on the buss mess everything up? The answer is write a program an try it =0)

I would love to colaborate with someone on this. let me know if yo uare interested.

David
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#12
Re: flashcart for sale??
Posted on: 2006/6/19 1:42
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
If you've actually got some of this past the design phase I'd love to help.

As I said before I was originally thinking of using the CS and Exp(ansion) select lines in order to activate the flash /WE line. Problem is its been so long since I looked at this I've long forgotten what line activates when.
Last I remember I (think I) figured out one of the lines would need to be inversed for everything (ROM, SRAM/EEPROM and /WE) to operate happily, but as its just been too long, don't take my word on that.

I just reread the 29F040 flash spec sheet recently and the whole rewrite sequence. It says it needs 6 codes to complete a sector/whole erase, and 4 to program a byte. Any idea if you can erase byte by byte?

Also, any idea if the erase/program sequence only needs /WE active during each command (with breaks in between)? The reason is that if you were to tie /WE to EXP it would go low (or high or whatever) after each byte is sent.

I'd be happy to write something to test erasing/programming. It's been ages since I've done anything VB, and I have a few weeks of holidays coming up.

About the bootloader, In order to keep it as small as possible I was thinking of doing the following:
* absolute minimal code necessary to activate VB
* check to see if COMCNT line is high (this would be pulled high by programmer)
* if line low, continue to ROM boot address (actual address would be moved somewhere else in ROM to accommodate bootrom address)
* if high, set xfer clock to external, prepare for link communication (can't remember exact method atm)
* set addr pointer to 0 (or somewhere)
* continuously poll (can't remember addr name - bit that tells you transfer complete). If (xfer contents register) is not zero, copy contents of register to pointer, inc pointer by 1. If it is zero, reset pointer to initial location and execute RAM code.

In order to reduce code, an acknowledgement is not included, but may be needed

This code would allow you you posibly load a secondary loader into RAM, which would then do more in-depth communication and checking.
My hope is to keep it as small as possible in order to reduce the risk of running out of free ROM space. I was thinking of possibly using that null area within the header to store the original ROM boot location, in order to identify if the ROM has in fact been changed (AFAIK all ROMs+tools have that area as null).


...Thats all I can think of atm. I'll try and look for my old notes on the select/enable lines.
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#13
Re: flashcart for sale??
Posted on: 2006/6/19 11:37
Newbie
Joined 2006/6/14
Germany
2 Posts
Long Time User (13 Years)
the 29f040 cannot be erased bytewise, i think they can be erased sector-wise tho.
this means most likely you should stick to y µC solution if you want to make your cart compatible to the original games...
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#14
Re: flashcart for sale??
Posted on: 2006/6/21 2:07
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
:) Don't have much time to explain ATM, but: http://dogp.home.comcast.net/VirtualBoy/CartPCBs/cartpcb.htm . Works great... I'm not sure how many will be available, but of course dev'rs get dibs over someone just too cheap to buy Space Squash and Insmouse ;) .

Working on programming in circuit over the link port.

DogP
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#15
Re: flashcart for sale??
Posted on: 2006/6/21 3:22
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
...There goes my money making scheme

But its nice to see someone is making carts


Any idea on price yet?
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#16
Re: flashcart for sale??
Posted on: 2006/6/21 4:50
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
No idea yet... I've gotta take care of a few people first, then I'll see how many are left. I'm not really sure about programming though... I figure the link port would be great, but then we'd need to make a link port connector :P . No problem for me with my RJ45 connector, but I don't think everyone wants to mod their VB.

Right now it's easiest for me to just pop the chips out, burn, and replace... but I'm sure everyone else wouldn't want to buy an EPROM programmer to go with their cart ;) .

DogP
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#17
Re: flashcart for sale??
Posted on: 2006/6/21 5:16
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
Any ideas on just how we can make a cheap link port connector? I know about the SNES/N64/GC AV cable hack, but thats just too much mess & trouble for what its worth. I tink I remember RunnerPack saying something about a 5.25" floppy connector, but I'll have to confirm that. That, and those things are hard to come by nowadays.

And about a bootloader, any ideas of your own? I quickly dropped the idea of an internal bootrom on the cart as it would take up space, but that only leaves injecting the loader into each ROM as its copied.
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#18
Re: flashcart for sale??
Posted on: 2006/6/21 6:35
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
Not sure about the link port connector... I figure it's gonna have to be a custom molded thing... for the bootloader I was thinking throw a really small piece into the unused interrupt vectors that just copies from the link port directly into memory, probably controlled by COMCNT. When COMCNT changes, stop copying and jump to where you copied the program to.

I'm just worried about which vectors we can use that aren't used by any game, or make it change depending on the game... and if it fails, then the cart is dead :( . Of course we should be able to use the game info section, but that may not be enough I was also thinking about using seperate boot chips, then swap them to flash the game... that way you don't worry about killing your cart, but then you've got a socket and need to swap chips. It would be a lot easier though ;) .

DogP
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#19
Re: flashcart for sale??
Posted on: 2006/6/21 7:19
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
lol, your loader sounds exactly like mine, even my original 'squeeze it into empty interrupt space' idea.
Only thing different is stopping COMCNT to signify end of transmission. That would allow some code to be dropped from the loader (albeit a few instructions), but would introduce a COMCNT poll upon each byte received.

As for the free space idea, I guess the program responsible for flashing the ROM would need to search through each interrupt and figure out which aren't used. If all are used, hope that nothing else is using the area between the ROM header and interrupts.


...And on the 5 1/4" FDD connector idea, any idea what its called? I've tried Googling for it, but all I've found out is the 3 1/2" connector is an IDC-34 pin.
I have a ton of old FDD cables at home, but I'd still love to be able to find one I can cut down and solder on to a PCB, which if done right could house the USB microcontroller(s) and a USB socket for a PC cable to plug into. Unfortunately the cables aren't PCB mounted. so even if I did use them I'd still have the FDD cable running to a board, instead of it fitting neatly underneath the VB/linkport.

...And as for the code, you never know - there may even be enough room to allow for a micro controller->VB->PC relay code allowing the VB controller to be used as a USB gamepad.
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#20
Re: flashcart for sale??
Posted on: 2006/6/21 8:31
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
Heh... I've already got a VB controller that I'm using as a USB gamepad: http://retrousb.com/virtualboy.html ... it's really sweet, I just wish I had more time to program so I could use it more :P .

DogP
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