Forums

Sega Master System / Mark III / Game Gear
SG-1000 / SC-3000 / SF-7000 / OMV
Home - Forums - Games - Scans - Maps - Cheats - Credits
Music - Videos - Development - Hacks - Translations - Homebrew

View topic - SMS Homebrew Carts

Reply to topic Goto page Previous  1, 2, 3, 4, 5  Next
Author Message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Sun Mar 30, 2014 7:06 pm
I was wondering about how many chances there are to use such a cart also for multiple homebrew. I mean, a collection of homebrews which aren't using mappers at all would be quite easy (put a 'menu homebrew' at the ROM page 0 and when the player selects an item it will switch banks according to the chosen item and jump back to $0000) but having homebrew that uses ROM paging would require some more effort, such as having a ROM bank LUT somewhere in each of them and 'patch' the LUT with proper values when preparing the cart. This doesn't seem an impossible task, actually... but I'd like to hear other homebrewer's opinion :)
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 2:49 pm
I managed to produce mechanical drawings from the SMS cartridge step files so kindly provided by a forum member. We're one step closer to a full homebrew cart product. I'm going to get a few of these in rapid prototype to make sure everything looks good...

Obviously a major hindrance still is cost for plastic molds, there will have to be a large enough demand for these in order to justify the NRE cost of molds.
SMS-HB-Back.png (55.29 KB)
SMS-HB-Back.png
SMS-HB-Front.png (50.26 KB)
SMS-HB-Front.png

  View user's profile Send private message
  • Joined: 08 Dec 2013
  • Posts: 200
Reply with quote
Post Posted: Tue Apr 01, 2014 3:47 pm
You should talk to the author of DiggerChan -- he had new carts made in batches of 25 or less, so must have already largely solved the "getting cases cheap" part, perhaps he could provide some guidance?

I think there would be demand given a bit of publicity in the right places; and a small Kickstarter or IndieGoGo could work for getting a big enough first batch done. This would require a more "polished" final product though (i.e. cart, box, manual -- much like StoneAgeGamer's editions of the EverDrive).
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 3:49 pm
Kroc wrote
You should talk to the author of DiggerChan


Anyone know how I can get a hold of him?
  View user's profile Send private message
  • Site Admin
  • Joined: 08 Jul 2001
  • Posts: 8702
  • Location: Paris, France
Reply with quote
Post Posted: Tue Apr 01, 2014 4:40 pm
Quote
Obviously a major hindrance still is cost for plastic molds, there will have to be a large enough demand for these in order to justify the NRE cost of molds.

Any idea of the costs/quantity involved here?

If we can manage to design all the components to make nice homebrew games, we could setup a system where we collectively invest funds to do an initial batch of "empty" games (board/case/boxes). Let's say we invest together into making 500-1000 we can sell them back at near-cost to homebrew makers over the courses of a few years (with minimum orders of say, 20), it is a fairly safe bet. That would make the homebrew scene instantaneously more attractive.
  View user's profile Send private message Visit poster's website
  • Joined: 25 Feb 2013
  • Posts: 387
  • Location: Osaka
Reply with quote
Post Posted: Tue Apr 01, 2014 4:48 pm
I wish to see the mark III /japanese SMS version as well...
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 5:04 pm
Bock wrote
Any idea of the costs/quantity involved here?


First and foremost, all the work I'm doing only involves the cartridge shell, plastics for the cartridge box would probably follow a similar structure.

Plastic Molds
-I've received quotes ranging from $4,000 to $8,000 for a mold set (remember there are two pieces to the cartridge shell). Some manufacturers are willing to throw in 200-300 units in that price. After this initial cost shells would cost little more than $1. I'm still working with other manufacturers to see if a blanket pricing scheme is possible.

CNC Cutting
-CNC cutting in ABS is targetted to smaller quantities but is considerably more expensive. I've received a quote for $25 per shell (when purchasing 100) using this technology - this is the only quote I've received thus far. A slightly cheaper price here may be a good starting point to get the project on its feet.

3D Printing
-3D Printing, as I've seen thus far, is the most expensive solution. There may be manufacturers who offer 3D printing at a similar price point to CNC cutting, that is yet to be determined. This is a technology that is well-suited for rapid prototyping, but not mass manufacturing.

Bock wrote
Let's say we invest together into making 500-1000

I really like your suggestion, assuming successful hardware development on my end, I would definitely participate in such a campaign.
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 5:05 pm
kamillebidan wrote
I wish to see the mark III /japanese SMS version as well...


This would imply having to jump the huge hurdle of mold costs a second time in order to manufacturer Mark III cartridges.
  View user's profile Send private message
  • Site Admin
  • Joined: 08 Jul 2001
  • Posts: 8702
  • Location: Paris, France
Reply with quote
Post Posted: Tue Apr 01, 2014 5:19 pm
Check out honestbob Mark III style cases making blog, he is discussing this. His cases look and feel great and he made them for a fraction of that price:
http://www.sc3000-multicart.com/sc3000-cart-case.htm
  View user's profile Send private message Visit poster's website
  • Site Admin
  • Joined: 19 Oct 1999
  • Posts: 14939
  • Location: London
Reply with quote
Post Posted: Tue Apr 01, 2014 5:49 pm
I think the labour cost is prohibitive for moulding. The other options are (I think) for almost-ready-to-go cases shipped to your door.

We don't need to make identical cases - just something that fits in the slot and lines up the cartridge edge connector enough to be usable. Could some simplification of the cartridge design make it cheaper?
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 6:04 pm
Maxim wrote
Could some simplification of the cartridge design make it cheaper?


The mold cost is not really affected by the design, I think it's more related to the final volume of the part.
  View user's profile Send private message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Tue Apr 01, 2014 7:58 pm
db-electronics wrote
I've received quotes ranging from $4,000 to $8,000 for a mold set (remember there are two pieces to the cartridge shell). Some manufacturers are willing to throw in 200-300 units in that price. After this initial cost shells would cost little more than $1. I'm still working with other manufacturers to see if a blanket pricing scheme is possible.


I believe it's too much, can't we CNC (or 3D print eventually) the mold set itself?
  View user's profile Send private message Visit poster's website
  • Site Admin
  • Joined: 19 Oct 1999
  • Posts: 14939
  • Location: London
Reply with quote
Post Posted: Tue Apr 01, 2014 8:13 pm
Last edited by Maxim on Tue Apr 01, 2014 8:23 pm; edited 1 time in total
I believe the mould is made by CNC machining metal. 3D printing in metal exists too.
  View user's profile Send private message Visit poster's website
  • Joined: 17 Sep 2013
  • Posts: 130
  • Location: Gravataí, RS, Brazil
Reply with quote
Post Posted: Tue Apr 01, 2014 8:14 pm
db-electronics wrote


Plastic Molds
-I've received quotes ranging from $4,000 to $8,000 for a mold set (remember there are two pieces to the cartridge shell). Some manufacturers are willing to throw in 200-300 units in that price. After this initial cost shells would cost little more than $1. I'm still working with other manufacturers to see if a blanket pricing scheme is possible.


Did you try to contact some everdrive vendor? maybe they already have the mold set done.
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 8:14 pm
sverx wrote
I believe it's too much, can't we CNC (or 3D print eventually) the mold set itself?


Injecting Molding Video

No you can't print a mold out of plastic unfortunately...[/url]
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 8:16 pm
gvx32 wrote
Did you try to contact some everdrive vendor? maybe they already have the mold set done.


Yes I did, the only molds being used right now are for Genesis carts (made by Watermelon) and for NES carts (made by RetroUSB). I'm not aware of anyone else making any cartridge shells, everyone is using donor carts...
  View user's profile Send private message
  • Site Admin
  • Joined: 19 Oct 1999
  • Posts: 14939
  • Location: London
Reply with quote
Post Posted: Tue Apr 01, 2014 8:24 pm
So if you made it trivially adjustable for Everdrive (regarding mounting points and maybe a break-off port for the SD card and USB) you'd have a bigger market for Everdrive shells that don't look as crappy as a Sega cartridge you've mangled a hole into (like mine).
  View user's profile Send private message Visit poster's website
  • Joined: 17 Sep 2013
  • Posts: 130
  • Location: Gravataí, RS, Brazil
Reply with quote
Post Posted: Tue Apr 01, 2014 8:39 pm
did you check http://www.stoneagegamer.com/master-everdrive-deluxe.html ?

the shells doesnt seen donors.
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 01, 2014 8:42 pm
gvx32 wrote
did you check [http://www.stoneagegamer.com/master-everdrive-deluxe.html]?

the shells doesnt seen donors.


Ryan paints donor shells. I asked him about Master System carts and, if I recall correctly, he said the Master Everdrives don't sell enough to warrant anything else but donor carts.
  View user's profile Send private message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Tue Apr 01, 2014 8:58 pm
db-electronics wrote
No you can't print a mold out of plastic unfortunately...


I never meant plastic, I though about some suitable material (metal for instance)
BTW this site sells a SMS adapter with his own case (look at the pictures) so maybe they have some supplier which has a mold already and maybe we can order some shell?
  View user's profile Send private message Visit poster's website
  • Joined: 01 Jan 2005
  • Posts: 360
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Wed Apr 02, 2014 2:03 pm
db-electronics wrote
Yes I did, the only molds being used right now are for Genesis carts (made by Watermelon) and for NES carts (made by RetroUSB). I'm not aware of anyone else making any cartridge shells, everyone is using donor carts...


AtariAge has a lot of volume, surely they must have industrially made cartridges? There is also the RGCD in the UK making C64 cartridge shells in several colours, and I'm sure the MSXers have some solution for their MegaROMs.

How big is the difference between Genesis and Master System carts? There is already some difference between European and Japanese Mega Drive carts, but nothing so big it can't be solved with a small hacksaw.
  View user's profile Send private message Visit poster's website
  • Joined: 17 Sep 2013
  • Posts: 130
  • Location: Gravataí, RS, Brazil
Reply with quote
Post Posted: Wed Apr 02, 2014 2:36 pm
How about talk to the everdrive vendors and digger chan´s author to share the costs of a mold?
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Wed Apr 02, 2014 2:51 pm
gvx32 wrote
How about talk to the everdrive vendors and digger chan´s author to share the costs of a mold?


I mentioned this earlier, this is not an option for the vendors I spoke to. The Master Everdrives don't sell well enough for them to justify any kind of investment...
  View user's profile Send private message
  • Joined: 17 Sep 2013
  • Posts: 130
  • Location: Gravataí, RS, Brazil
Reply with quote
Post Posted: Wed Apr 02, 2014 3:11 pm
db-electronics wrote
gvx32 wrote
How about talk to the everdrive vendors and digger chan´s author to share the costs of a mold?


I mentioned this earlier, this is not an option for the vendors I spoke to. The Master Everdrives don't sell well enough for them to justify any kind of investment...


thats odd, I mean, they have to buy cards to be donnors any way, with a reasonable priced mold, this would eventually be cheaper. Well, I guess they know their business better than me.

did you try to contact furrtek? he have a brand new shell for his animous prototype: http://furrtek.free.fr/?a=animusxs
  View user's profile Send private message
  • Site Admin
  • Joined: 19 Oct 1999
  • Posts: 14939
  • Location: London
Reply with quote
Post Posted: Wed Apr 02, 2014 3:22 pm
A Mega Drive cartridge's edge connector is wider than a Master System cartridge, I think. Thus you can't share shells. Even less so if you want to have the PCB supporting cylindrical thingies in the "standard" places to fit Everdrives.

My feeling is that either some Chinese factory will knock out cheap shells that are a bit crappy for not much money, or we will have to go for injection moulding and hope to make the money back in a few years...

Loose SMS carts can be got pretty cheap, in bulk. Collectors don't like loose carts, and you're removing the labels anyway so they can be in pretty bad condition. Everdrive sellers may only need 10-20 per year.

My French isn't good enough (and nor is Google's) to figure out what Furrtek did, maybe he'll drop in and let us know. It sounds like prototypes from Chinese injection moulders, thus maybe just 3D printed?
  View user's profile Send private message Visit poster's website
  • Joined: 01 Jan 2005
  • Posts: 360
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Wed Apr 02, 2014 6:40 pm
Maxim wrote
A Mega Drive cartridge's edge connector is wider than a Master System cartridge, I think. Thus you can't share shells. Even less so if you want to have the PCB supporting cylindrical thingies in the "standard" places to fit Everdrives.


If a Megadrive connector is wider, and the existing shell is for Megadrive PCBs, I don't see why that would pose a problem. If there are other PCB supports, you don't really need the PCB gate at the bottom as a support.

Maxim wrote
My French isn't good enough (and nor is Google's) to figure out what Furrtek did, maybe he'll drop in and let us know. It sounds like prototypes from Chinese injection moulders, thus maybe just 3D printed?

A service called Protomould, it seems.
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Wed Apr 02, 2014 6:46 pm
Maxim wrote
My French isn't good enough (and nor is Google's) to figure out what Furrtek did, maybe he'll drop in and let us know. It sounds like prototypes from Chinese injection moulders, thus maybe just 3D printed?


Je savais qu'être francophone me serait utile un de c'est jour!

I'll read furrtek's website later tonight and find out what's going on...
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Wed Apr 02, 2014 7:48 pm
Nevermind I read it immediately! Here follows a translation of the important parts from Furrtek.

13/08/2013
He received the top half of the cartridge (3D printed or cut, doesn't specify) from Sculpteo. His first prototype was mostly validated except that the slot for the PCB wasn't wide enough. Had a discussion on "Yaronet" about a cartridge compatible with both SMS and MD which is why he is waiting on getting a prototype for the bottom half of the shell.

18/08/2013
Modified the shell design, sent for prototyping and expects parts to be received by the 23rd. He also ate a mildly appreciable pizza. (not kidding about the pizza! - original "Mangé une pizza moyennement appréciable.")

19/08/2013
He spent the day learning about chinese mold makers. Protomold, he says, are not the cheapest but they are the fastest. There is no clear indication of which company he uses.

06/09/2013
Prototype is validated, all fits perfectly. The plastic is white because this was the cheapest option.

Other than having an initial prototype done at Sculpteo, and mentioning that Protomold would offer then fastest turnaround, there is no clear mentioning of which company built the white prototype cases.
  View user's profile Send private message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Wed Apr 02, 2014 8:48 pm
Let's bring that guy into this discussion immediately! :D
Seriously, it would be a win-win.
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Wed Apr 02, 2014 8:52 pm
sverx wrote
Let's bring that guy into this discussion immediately! :D
Seriously, it would be a win-win.


I'll send him an email (in French!) and ask him to come join our discussion.
  View user's profile Send private message
  • Joined: 04 Jul 2010
  • Posts: 546
  • Location: Angers, France
Reply with quote
Post Posted: Wed Apr 02, 2014 9:00 pm
Last edited by ichigobankai on Wed Apr 02, 2014 10:17 pm; edited 1 time in total
Has I'm french and have followed Animus thread :

Furrtek have explained on Yaronet Animu's thread that the cartridge will be "on demand", made with 3d printers because molds are far too expensive (~2000€ for each parts...).
3D printed cartridge will cost ±30€.

Unless a very huge demand I don't think he will change his plans... But you can always send him a message.

Apart from that, the cartridge design "huge sticker" and white color are very nice ideas !

Pour finir et en francais, mes félicitations à db-electronics pour son travail très pro sur ces futures cartouches qui seront - j'en suis sûr - très utiles pour la scène homebrew master system !
  View user's profile Send private message
  • Joined: 11 Mar 2014
  • Posts: 91
  • Location: France
Reply with quote
Post Posted: Wed Apr 02, 2014 9:39 pm
ichigobankai wrote
Apart from that, the cartridge design "huge sticker" and white color are very nice ideas !


I'm not really fond of the idea. It does look cool, and it works on the Megadrive as the cartridges stick out more, but on Master System they're deeply inserted in the system. Many of my games have sign of wear on the front up to right below the grooves. If the plastic gets worn I can't fathom what would happen to a sticker after a few insertions.

[edit] Then again, maybe the side ridges will be enough to prevent such tear to happen.
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Wed Apr 02, 2014 10:10 pm
ichigobankai wrote
Has I'm french and have followed Animus thread :

Furrtek have explained on Yaronet Animu's thread that the cartridge will be "on demand", made with 3d printers because molds are too far expensive (~2000€ for each parts...).
3D printed cartridge will cost ±30€.

Unless a very huge demande I don't think he will change his plans... But you can always send him a message.

Apart from that, the cartridge design "huge sticker" and white color are very nice ideas !

Pour finir et en francais, mes félicitations à db-electronics pour son travail très pro sur ces futures cartouches qui seront - j'en suis sûr - très utiles pour la scène homebrew master system !


Thanks for providing insight on the "Yaronet" thread, which as we now know, indicates that shells are 3D printed on demand. I'll still reach out to Furrtek about this project, perhaps he will want to contribute and likewise myself on his project.

Merci pour ton encouragement ichigobankai! C'est bien de finalement rencontrer des gens ici qui fournissent de l'aide à un projet. Je participe aussi sur d'autre forum et malheureusement c'est un peu moins positif là.
  View user's profile Send private message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Thu Apr 03, 2014 8:10 am
db-electronics wrote
I've received quotes ranging from $4,000 to $8,000 for a mold set (remember there are two pieces to the cartridge shell). Some manufacturers are willing to throw in 200-300 units in that price. After this initial cost shells would cost little more than $1.


Do you think it would be possible to build our shell developing the two halves of it as the same piece instead of two different pieces?
I mean, if we develop it "symmetric", that would cut the initial cost in half, wouldn't it?

As for the french... J'ai étudié français à l'école but it was too long ago :D
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Thu Apr 03, 2014 8:21 pm
I think it would be very difficult to make a shell that is symmetrical yet still has locking features for the shell and mounting posts and provisions for screws.
  View user's profile Send private message
  • Joined: 17 Sep 2013
  • Posts: 130
  • Location: Gravataí, RS, Brazil
Reply with quote
Post Posted: Thu Apr 03, 2014 8:37 pm
is not possible to use just one of the halfs of the genesis mold, and than make a mold for the other half?
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Thu Apr 03, 2014 8:39 pm
gvx32 wrote
is not possible to use just one of the halfs of the genesis mold, and than make a mold for the other half?


The mounting posts wouldn't line up as they are in different spots on a MD board vs. an SMS board.
  View user's profile Send private message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Thu Apr 03, 2014 8:58 pm
db-electronics wrote
I think it would be very difficult to make a shell that is symmetrical yet still has locking features for the shell and mounting posts and provisions for screws.

I never meant to say it would be easy, I was just wondering if there are reasons that makes that impossible. I don't see any, but I'm a newbie... fortunately this place hosts lots of very knowledgeable people, so maybe one of them would help us solve this :)
  View user's profile Send private message Visit poster's website
  • Joined: 17 Sep 2013
  • Posts: 130
  • Location: Gravataí, RS, Brazil
Reply with quote
Post Posted: Thu Apr 03, 2014 10:24 pm
Here in Brazil there were some pirate master system games. Personally I never saw one.

[http://corujasnews.blogspot.com.br/2010/09/games-cartuchos-piratas-do-master.html]

Any way, I know that would be pretty hard to find, but, maybe some plastic manufacturer still have molds like that.
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Sun Apr 06, 2014 11:36 pm
Between two snow storms and a flooded basement (Yay Canada!) I managed to route all connections on the homebrew cart PCB. I still have to straighten the connections, do a general cleanup and pour ground planes before releasing this to the PCB fabricators.

I'm going to start developing the burning board which shouldn't be too difficult since there really is no dimensional constraints on it.

I would like to get some input as to how you guys think the burning board should behave. At first I wanted to include a simple SPI connection on the homebrew cart for programming but alas I can't fit that many registers in the CPLD. The homebrew cart will have to be programmed by some parallel means through the edge connector.
SMS-HBb.PNG (49.51 KB)
SMS-HBb.PNG

  View user's profile Send private message
  • Joined: 17 Sep 2013
  • Posts: 140
  • Location: TC, MI
Reply with quote
Post Posted: Mon Apr 07, 2014 1:44 am
Looking at the edge connector, there are two +5v pins.

I suggest you connect the farthest right +5v pin as the /WE pin and not VCC. When the cart is in the console, the WE pin on the ROM is pulled high becuase it will be connected to +5v in the console, but when inserted into your programmer, it may be high or low depending on your needs.

Similar to this here:
http://raphnet.net/electronique/genesis_cart/genesis_8mbit_cart.png
Read the note on the far left if you didn't understand what I was trying to describe.
  View user's profile Send private message Visit poster's website
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Mon Apr 07, 2014 7:46 am
db-electronics wrote
The homebrew cart will have to be programmed by some parallel means through the edge connector.


It sounds good :)
Just to be sure, everything else we discussed here is confirmed? (I mean have few different Flash size configurations, have battery RAM optionally...)
Also I was thinking about having something that could help everybody identify that it's a repro board without having to open the shell, I was worrying about someone trying to fake original games... 'REPRO' written somewhere on the edge connector would be enough, maybe in the place of an unused contact?
  View user's profile Send private message Visit poster's website
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Mon Apr 07, 2014 12:30 pm
Jazzmarazz wrote
I suggest you connect the farthest right +5v pin as the /WE pin and not VCC.


I considered this, but I'm heavily leaning towards not doing it because I don't want to remove the future possibility of programming carts directly in the SMS. It wouldn't be to hard to make a USB to Sega Card dongle to achieve this in the future. Actually, such a device would be more mechanically reliable than a burning device with a 50-pin edge connector.

As for write protection, the Sega Mapper has a write protect bit in bit 7 of register $FFFC and you also need to follow a specific algorithm to program each byte in the flash; therefore I think accidental writes are VERY unlikely to occur.

sverx wrote
Just to be sure, everything else we discussed here is confirmed? (I mean have few different Flash size configurations, have battery RAM optionally...)


Yes it's all there. Referencing the latest PCB picture I uploaded a few posts ago:

  • The upper most IC in the top left is the SRAM for save files
  • Directly below the SRAM is the CPLD which will implement the mappers
  • The top left 2x5 connector is the programming port for the Altera CPLD
  • The large circle is the footprint for the battery holder
  • The two rightmost ICs are the flash chips


At a minimum, the cart requires at least the CPLD and one flash chip (1 Mega Power minimum) to operate. These flash chips come in 1, 2 and 4 megabit variants which are all pin compatible. The SRAM IC and the battery circuitry can all be omitted if not needed.

sverx wrote
Also I was thinking about having something that could help everybody identify that it's a repro board without having to open the shell, I was worrying about someone trying to fake original games... 'REPRO' written somewhere on the edge connector would be enough, maybe in the place of an unused contact?


I think this is an excellent idea! I also had the same worries about fake games. I will think of something to clearly identify this even if it is in a cartridge shell.
  View user's profile Send private message
  • Joined: 25 Feb 2013
  • Posts: 387
  • Location: Osaka
Reply with quote
Post Posted: Mon Apr 07, 2014 3:51 pm
use oshpark and get cool purple boards ;)
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Mon Apr 07, 2014 3:55 pm
kamillebidan wrote
use oshpark and get cool purple boards ;)


Haha! My preferred PCB fabricator charges a premium for soldermask colours other than green :(
purple.jpg (33.39 KB)
purple.jpg

  View user's profile Send private message
  • Joined: 05 Sep 2013
  • Posts: 3936
  • Location: Stockholm, Sweden
Reply with quote
Post Posted: Tue Apr 08, 2014 2:35 pm
db-electronics wrote
[...] and you also need to follow a specific algorithm to program each byte in the flash; therefore I think accidental writes are VERY unlikely to occur.


So it means a program could in fact change some of the Flash contents? (I'm thinking if this would be useful for a simple savegame...)
  View user's profile Send private message Visit poster's website
  • Joined: 25 Feb 2013
  • Posts: 387
  • Location: Osaka
Reply with quote
Post Posted: Tue Apr 08, 2014 3:01 pm
yes. still, to write flash you need to erase a whole sector of it (it depends, but usually ~16k) and then you can start writing it.
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 08, 2014 3:19 pm
The flash I'm using has a 4KB sector size. With the SMS's 8KB ram it could actually be feasible to use a sector of flash as a save file.

As kamillebidan mentioned, you need to erase a whole sector before making any changes to it (even if all you need to do is change 1 bit). Therefore you'd have to copy the 4KB sector into ram, make the necessary changes, and write it back to the flash.
  View user's profile Send private message
  • Joined: 11 Mar 2014
  • Posts: 91
  • Location: France
Reply with quote
Post Posted: Tue Apr 08, 2014 6:18 pm
Last edited by jarreboum on Tue Apr 08, 2014 7:00 pm; edited 1 time in total
(please pardon my lack of knowlegde on such thing but)

I thought eeprom could only be rewritten after being wiped out with UV? this isn't the technology we're talking about? Are you planning on using some sort of non volatile SRAM?

Wouldn't that mean the shelf life would be consequently reduced? I would have thought you would use some sort of one-time programmable ROM for the end user, keeping the rewritable options for beta-testing.

[edit] ok, 100 years is more than fair enough, I guess :)
  View user's profile Send private message
  • Joined: 06 Dec 2013
  • Posts: 335
  • Location: Canada
Reply with quote
Post Posted: Tue Apr 08, 2014 6:41 pm
jarreboum wrote
(please pardon my lack of knowlegde on such thing but)

I thought eeprom could only be rewritten after being wiped out with UV? this isn't the technology we're talking about? Are you planning on using some sort of non volatile SRAM?

Wouldn't that mean the shelf life would be consequently reduced? I would have thought you would use some sort of one-time programmable ROM for the end user, keeping the rewritable options for beta-testing.


I'm using SST Flash, it has data retention greater than 100 years and 100,000 cycle endurance.
  View user's profile Send private message
Reply to topic Goto page Previous  1, 2, 3, 4, 5  Next



Back to the top of this page

Back to SMS Power!