A Sega Genesis repro PCB with FeRAM support

[Ziggy]

I've been thinking about the microcontroller way for sometime now, i've been using AVR and STM32 microcontrollers for years now, even made my own USB EPROM programmer using the STM32 and they are wonderful little chips. I would be even possible to use Flash memory instead of an EPROM make USB programed cartridge, but i don't really know if this doesnt turn the project in some kind of poormans Everdrive, not thats a bad thing, i just don't know if there is interest in something like this. Using a MCU, the information about which ROM, which size, which bank and the corresponding RAM location could be fed to the chip and it could care about this aspect of the game selection for the user.

Well there must be interest in this sort of cart because a few people are making them. I think the main draw is for people that don't know how to solder can buy one of these pre-made and simply flash a game to the cart. So it's essentially a DIY repro cart. Infinite NES Lives makes one for NES and SNES. Retro Stage makes them for GB/C/A, NES, SNES, N64 and Genesis. And Krikzz has one for Genesis. There might be others out there, but those are the ones I know of.

http://www.infiniteneslives.com/hardware.php

https://retrostage.net/index.php/shop/

https://krikzz.com/store/home/38-flashk ... er-md.html

The old Tototek flash carts also worked in a similar way, but the programmer had a parallel interface instead of USB. The above carts are all for single game if I'm not mistaken, but the Tototek carts works more closely to what you're describing. If you flashed a single game to the Tototek cart, it would boot that game like any other homebrew cart. But if you flashed more than one game to the cart, it would first load a menu where you could select which game you wanted to boot. It had a limit of 4 games at once, and could only hold 1 save at a time.

Yes, they are quite expensive, more so because they're 5V compatible and not in production anymore, there are new FeRAM designs that are cheaper, but most of them have serial I/O or are 3.3V maximum. I've searched for other non volatile chips, but even in 2020, the tecnology is quite there yet

Yeah, it's getting harder and harder to find 5v tolerant stuff these days. I was looking at an EEPROM that is still in production that looked like a (more or less) drop in for the Saturn, but I ended up getting the FeRAM because I wasn't sure if the Saturn would be able to write to the EEPROM. As for my own cart designs, I'm sticking with 5v tolerant stuff for now. My plan is to design slightly more complicated carts one at a time until finally I'll attempt to make one using all or mostly 3.3v parts.

[Soniccd123]

Well there must be interest in this sort of cart because a few people are making them. I think the main draw is for people that don't know how to solder can buy one of these pre-made and simply flash a game to the cart. So it's essentially a DIY repro cart. Infinite NES Lives makes one for NES and SNES. Retro Stage makes them for GB/C/A, NES, SNES, N64 and Genesis. And Krikzz has one for Genesis. There might be others out there, but those are the ones I know of.

http://www.infiniteneslives.com/hardware.php

https://retrostage.net/index.php/shop/

https://krikzz.com/store/home/38-flashk ... er-md.html

The old Tototek flash carts also worked in a similar way, but the programmer had a parallel interface instead of USB. The above carts are all for single game if I'm not mistaken, but the Tototek carts works more closely to what you're describing. If you flashed a single game to the Tototek cart, it would boot that game like any other homebrew cart. But if you flashed more than one game to the cart, it would first load a menu where you could select which game you wanted to boot. It had a limit of 4 games at once, and could only hold 1 save at a time.

Well, thats true and made me think about it, maybe in the future i may design something like this, its just that it adds some layers of complexity that i'm not ready to work on, like programming loaders that run on the console, etc; its just that there is a lot of unknowns for me and i will need more time to really grasp on these things and study how to make them work. For now, i'm myself am using my own cart writer, just like krikzz programmer, that you can connect the full cart on and write it or read it, i can share the schematics and PC-side software utilities if it is of interest as i have been using it for quite a long time and it proved reliable.

Yeah, it's getting harder and harder to find 5v tolerant stuff these days. I was looking at an EEPROM that is still in production that looked like a (more or less) drop in for the Saturn, but I ended up getting the FeRAM because I wasn't sure if the Saturn would be able to write to the EEPROM. As for my own cart designs, I'm sticking with 5v tolerant stuff for now. My plan is to design slightly more complicated carts one at a time until finally I'll attempt to make one using all or mostly 3.3v parts.

I plan to use some 3.3V parts in my next projects, i have some ideas of how to safely level shift what is needed from the earlier said programmer that i made, which uses a 3.3V STM32 MCU for USB comunication, lets see how it goes!

[N2_]

Are people still interested in this project?

I'd like to see a revised board with a 2nd FeRAM chip attached to the other half of the Data bus so 16-bit wide values can be saved, such a version should enable the execution of code directly from the save area and would make this a nice developer cart. one might even go so far as to write a serial boot loader to load S-records if a controller/EXT port in serial mode.

N2

P.S. Mill-Max-type single-pin socket cups are awesome! these 1.1mm nominal O.D. sockets will flush mount to a PCB board allowing you to fit socketed EPROMs into an OEM cart shall casing without modification. all that is required to fit these sockets is to open up the hole side for you chips so the body of the socket can fit in the now larger holes.