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  • Joined: 01 Jul 2022
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making your own repro cartridge
Post Posted: Fri Jul 01, 2022 6:45 am
Hi all!

I'm interested to make my own cartridge of the SMS patched version of Sonic Triple Trouble, but I'm wondering what might be the cheapest way to get a cartridge PCB and a programmable chip? I seen some complete programmable SMS cartridges you can buy, but you need a special programmer for them also. I already have a programmer, a TL866CS, so kinda wonder if it's possible to make use of that and solder in a suitable chip myself with that Sonic game on it? thougt it might be cheaper to do it that way if possible.
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Post Posted: Fri Jul 01, 2022 10:40 pm
denfin wrote
what might be the cheapest way to get a cartridge PCB and a programmable chip?


The cheapest way, strictly speaking, is probably to scavenge an orignal 4Mega cartridge for its mapper chip, although personally I think it's a shame to do it.

The mapper is the biggest challenge in making your own cartridge. Triple Trouble is a 512KB game, so needs 5 bits of ROM banking. Assuming it doesn't switch bank 0 and assuming it only uses system RAM that means at a minimum it will need mapper circuitry with 25 inputs and 6 outputs by my reckoning, as well as at least 10 flip-flops.

If you're not using an original Sega mapper chip, the alternative is to create your own with a PLD and since you say you don't want to invest in any programming hardware other than your TL866 that narrows it down considerably! I reckon it might just about be possible to use something like 2x 22V10 GALs, which you can still get, in DIP packages, and which the TL866 can definitely program. Otherwise if you want something a little bit more advanced there are tons of CPLDs that would do the trick, but programming might get a bit trickier. Plus it's an absolute b*tch to get semiconductors right now!

If you're thinking of getting PCBs made up, that is crazy easy and cheap to do even for small quantities.

Most people who sell homebrew carts online I presume are applying some markup as they don't come that cheap. Not sure if there are Open Source Hardware designs out there to use?
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Post Posted: Fri Jul 01, 2022 10:51 pm
Thanks for the answer! And hm... sounds a bit more complicated than I thought XD and yeah I don't really feel like ruining an existing game aslo, would be a shame as you said!

Is there anyone in the EU that sells any programmable master system cartridges or something? I found someone in the US and Japan i think, but yeah, then I have to pay extra import and handling fees also unfortunatley.
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Post Posted: Sat Jul 02, 2022 2:46 pm
Out of interest, are you more looking for a way to flash a single game to a cart and have it be permanently on there, or more of an Everdrive scenario where you can load many games from a single cartridge?
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Post Posted: Sat Jul 02, 2022 5:29 pm
I want to make a single game, I will probably print out a cover for it and put it in a case also, I know of the everdrive things, but think it's nicer o have a dedicated cartridge :)
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Post Posted: Sat Jul 02, 2022 9:15 pm
Cheapest and easiest: after burner + 29f040
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Post Posted: Sat Jul 02, 2022 9:53 pm
Hm, I looked it up and After Burner seems very cheap, kind of a shame to reuse another cartridge, but yeah, seems to be the cheapest option tho, and then I don't need to get a new programmer that I will probably only use once, the TL866 I have seems to be compatible with 29F040, I can see it's listed in the software that comes with it, so maybe I go with reusing another cartridge after all.

But so, do I just burn the patched Sonic Triple Trouble ROM to a 29F040 chip, then just take out the old After Burner ROM chip and solder the new one in place? Nothing that needs to be altered or something?
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Post Posted: Sun Jul 03, 2022 9:54 am
Not sure if you've already seen it, but this thread may be relevant.

The boards now look to be $16 which feels about right to me having looked at the parts used. You have the cost of the programmer but that's a one off. Not sure where you are in Europe, but in the UK you don't have to pay any import duty for goods less than £135. Perhaps it's similar in other jurisdictions?

Of course, using an old cartridge is always going to be the cheapest option. If I were you I'd replace the old ROM with a DIP socket to be on the safe side unless you're very confident it will work first time!
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Post Posted: Sun Jul 03, 2022 10:16 am
Yeah I seen those, they seem very nice I have to say! but yeah, I'm from Sweden and unfortunatley I would have to pay import an handling fees for every single little thing from outside the EU... :( And yeah, I do not have any plans to make more games so would be pretty expensive unfortunatley, so I bought a copy of After Burner now for just like 12 USD including postage and bought a 29F040 chip for just like 4 USD including postage. And I have sockets already, so will try to use that :) But so it's just a simple swap of the chips? no extra stuff I need to do? Just wondering so I don't mess anything up! Cus I done something similar before with old Atari 2600 game PCBs, and on those I needed to lift some leg and add some wires and stuff.
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Post Posted: Sun Jul 03, 2022 11:20 am
Scouting around for definitive instructions on this forum didn't reveal anything that I could find, but I just popped open my own copy of Afterburner to double check and the only thing I think you might need to modify is looks to me like pin 1 of the cart ROM is not connected whereas on the 29F04 it's A18 (as per JEDEC EPROM standard).

A18 on the cart ROM appears to be pin 31, and is connected to pin 14 if the mapper chip (here 315-5235) so I believe you'll need to lift pin 31 of your 29F04 or DIP socket, and connect the original pin 31 pad to pin 1 of the 29F04 or DIP socket.
Pin 31 of the 29F04 is the write enable, so that needs to be connected to Vcc too, to make sure it's in read only mode.

I'll attach some pictures.

Everything else looks okay to me from a preliminary check.

EDIT: pics attached. I'd put in a jumper wire from the underside, just remember to lift the leg of the 29F04 / socket when you install it, and connect the lifted leg to Vcc.
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Post Posted: Sun Jul 03, 2022 12:20 pm
Thanks for the help and the pictures! And so you mean, pin 32 is the VCC connection? If i understand correctly?
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Post Posted: Sun Jul 03, 2022 12:26 pm
This is the original “cart mod” hack from way back which means many of the original references are lost. This is probably the canonical one:

https://web.archive.org/web/20090828183701/http://cgfm2.emuviews.com/smsflash.ph...
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Post Posted: Sun Jul 03, 2022 1:51 pm
Ah thanks Maxim, that's a much better guide than my hasty scrawlings!

Perhaps it would be nice to collate a sticky topic collecting the various hardware mods so it's easier to find them - thoughts?

denfin wrote
Thanks for the help and the pictures! And so you mean, pin 32 is the VCC connection? If i understand correctly?

Yep that's right, conveniently right next to ~WE on pin 31.
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Post Posted: Sun Jul 03, 2022 7:06 pm
Thanks for all the help! But hm, on that link from Archive.org, it says "You can leave WE# (pin31) unconnected." So, does it not matter too much if it's connected to VCC or not? Or maybe connect to VCC is better?
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Post Posted: Sun Jul 03, 2022 7:35 pm
I guess it wouldn't be there unless someone had tried it and found it to work, but in the datasheet it doesn't mention anything about leaving ~WE disconnected that I can tell and I would be surprised if there was an internal pull-up on that pin. The datasheet does say this:

Quote
Requirements for Reading Array Data
To read array data from the outputs, the system must
drive the CE# and OE# pins to VIL. CE# is the power
control and selects the device. OE# is the output con-
trol and gates array data to the output pins. WE# should
remain at VIH.


Personally I'd go with the datasheet on this one!
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Post Posted: Sun Jul 03, 2022 7:50 pm
Okay,guess I go with that then! :)
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