Open Hardware SNES Repro PCB with FeRAM support

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soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

Hello,

In the same vein that I shared my open hardware Genesis repro PCB, I am now sharing my SNES Repro PCB with the community. It is an open hardware project and everyone is welcome to modify and study it as needed. I've tested it extensively in the last months and I think that most bugs, especially correct save support for HiROM and LoROM are corrected.

So, here it is: https://github.com/soniccd123/SNES-FeRAM-Cart

Some of the PCB features:
  • ROM Support for up to 4MB
  • HiROM and LoROM software (set by jumpers)
  • 32KB of FeRAM for saving (256kb)
  • No need for backup battery
  • Rudimentary ROM bank switch (Permits multiple games on same ROM)
  • SuperCIC support, now confirmed working!
The github page contain all the Gerber files needed to produce the PCB as it is if one wants too. Also contains all the project in KiCad format for easy modification.

Be welcome to ask questions and make sugestions. I'm not a professional engineer and it may have flaws that i didn't noticed. Hope you enjoy and this helps someone!

Soniccd123

THINGS TO NOT FORGET WHEN BUILDING:
  • Check the chips orientation before soldering and powering on. KiCAD stock silkscreen for SMD components is quite bad showing correct orientation;
  • Byteswap the ROMs when writting;
  • If your board was build with a design before the 02/24/2021 commit, join U5 pin 20 with a 5V source (pin 1 is a good candidate).
Update 03/28/2021: The PCBs have been confirmed working by independent testing from other users (thanks @RetroSwin, @Online and @hobodozer). For those of you that used the designs made before 02/24/2021 must join U5 pins 20 and 1 with a short wire (thanks @DeLFuS for pointing out). Don't forget to write your ROMs byteswapped.
Last edited by soniccd123 on Sun Mar 28, 2021 5:53 pm, edited 3 times in total.
calima
Posts: 1745
Joined: Tue Oct 06, 2015 10:16 am

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by calima »

Is feram still as expensive as it used to be, many times the price of sram+battery?
soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

calima wrote: Sat Nov 14, 2020 1:02 am Is feram still as expensive as it used to be, many times the price of sram+battery?
Well, i don't know if its as expensive as it used to be, I got the chips for like 8 dolars for 5 chips. It was a personal choice for me because I really have some bad experiences with batteries lol.

But this can be easily modified in the project if you need. Find a suitable SRAM chip and the battery management circuitry, i think theres even chips pin compatible with the FM1808 that I used (The 62256 is pin compatible i think). There is plenty space in the PCB for adding the needed components.
DeLFuS
Posts: 6
Joined: Tue Feb 23, 2021 1:33 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by DeLFuS »

Hello!

I'm looking at your project and I find it very interesting. I have been looking for the FM1808 and have found 2 types FM1808B and the FM1808. Are both valid? or it has to be B. I have looked for the differences and I have found that model B is the substitute for normal and that the only difference is "Standby Current". Could you clarify this question for me, thank you. I have also seen that on your github they say that on your U5 pcb + 5v is not connected to pin 20. Is that so?

Thank you very much for your contribution to the retro community!
soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

DeLFuS wrote: Tue Feb 23, 2021 1:40 pm Hello!

I'm looking at your project and I find it very interesting. I have been looking for the FM1808 and have found 2 types FM1808B and the FM1808. Are both valid? or it has to be B. I have looked for the differences and I have found that model B is the substitute for normal and that the only difference is "Standby Current". Could you clarify this question for me, thank you. I have also seen that on your github they say that on your U5 pcb + 5v is not connected to pin 20. Is that so?

Thank you very much for your contribution to the retro community!
Hey, thank you very much!

I haven't really tested the non-B version of the FM1808, but it should work fine

Thank you for pointing the not connected U5 pin 20, facepalm to myself for letting such a stupid error go unnoticed, after i've produced the last prototype before sharing the project, i've made some needed adjustments based on tests and must have deleted that trace accidentally. Hope anybody has tried to built it like this because, while easy to fix, would prevent the cart to work at all. I guess thats the spirit of open projects, everybody can give insights and point problems to fix!

Will update it with a fix as soon as i get to my computer
DeLFuS
Posts: 6
Joined: Tue Feb 23, 2021 1:33 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by DeLFuS »

soniccd123 wrote: Wed Feb 24, 2021 10:49 am
DeLFuS wrote: Tue Feb 23, 2021 1:40 pm Hello!

I'm looking at your project and I find it very interesting. I have been looking for the FM1808 and have found 2 types FM1808B and the FM1808. Are both valid? or it has to be B. I have looked for the differences and I have found that model B is the substitute for normal and that the only difference is "Standby Current". Could you clarify this question for me, thank you. I have also seen that on your github they say that on your U5 pcb + 5v is not connected to pin 20. Is that so?

Thank you very much for your contribution to the retro community!
Hey, thank you very much!

I haven't really tested the non-B version of the FM1808, but it should work fine

Thank you for pointing the not connected U5 pin 20, facepalm to myself for letting such a stupid error go unnoticed, after i've produced the last prototype before sharing the project, i've made some needed adjustments based on tests and must have deleted that trace accidentally. Hope anybody has tried to built it like this because, while easy to fix, would prevent the cart to work at all. I guess thats the spirit of open projects, everybody can give insights and point problems to fix!

Will update it with a fix as soon as i get to my computer

Thanks to you. I've been looking at the gerber better and wanted to give an idea. It would be highly recommended to pass all the resistors, capacitors to SMD and the two 74HC245 in the front.

I comment on this because in this way you can ask the factory to assemble it directly by them and we only have to weld the SuperCIC and 27C322 by hand.

Similar would happen in the mega drive that you have also shared and I thank you very much. It would also be interesting to pass all the components to smd.

By the way, when I edit the gerber in Kicad of megadrive, 3 more capacitors appear if I update the Netlist. (C1, C3 and C4)
soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

DeLFuS wrote: Wed Mar 03, 2021 10:47 am Thanks to you. I've been looking at the gerber better and wanted to give an idea. It would be highly recommended to pass all the resistors, capacitors to SMD and the two 74HC245 in the front.

I comment on this because in this way you can ask the factory to assemble it directly by them and we only have to weld the SuperCIC and 27C322 by hand.

Similar would happen in the mega drive that you have also shared and I thank you very much. It would also be interesting to pass all the components to smd.

By the way, when I edit the gerber in Kicad of megadrive, 3 more capacitors appear if I update the Netlist. (C1, C3 and C4)
It may be a hard to re-route everything with all the chips on one side, but can be done, it just may take some time. Also, If you wan't give a try yourself, be my guest :)

About the capacitors, they're just decoupling capacitors that I forgot to delete in the schematic and netlist, don't worry about them. You can add them if you really wan't, but in my tests the cart works normally with the ones that are already there.
RetroSwim
Posts: 11
Joined: Tue Mar 09, 2021 4:09 am

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by RetroSwim »

Hi there soniccd!! First off thanks for your excellent work on this, I'd be lost without it!!

I sent the Gerbers off to China for manufacture just days before you issued the update for pin 20! D'oh! Easy to fix though, and thankfully I found this thread before I started banging my head against the wall hahaha.

I'm going to be using the PCBs to create repro's of Super Mario World romhacks for some friends (including the creators of those hacks).

They are 32Mb ROMs, so I'll be foregoing the bank select switch and installing wire links in R1-R4 to fix everything in place, and use the whole 27C322.

When choosing the components, I consulted the datasheets and found that the FM1808 can be substituted for the FM1808B or FM18W08, both of which seem to be more readily available on AliExpress.

The FM18W08 in particular seems to be everywhere, and it's simply the wide-voltage variant if the FM1808, which supports lower voltages with looser timings. At 5v, the timings are identical to the FM1808.

Anyway wish me luck! The PCBs should arrive in the next few days, pretty exciting!
soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

RetroSwim wrote: Tue Mar 09, 2021 4:19 am Hi there soniccd!! First off thanks for your excellent work on this, I'd be lost without it!!

I sent the Gerbers off to China for manufacture just days before you issued the update for pin 20! D'oh! Easy to fix though, and thankfully I found this thread before I started banging my head against the wall hahaha.

I'm going to be using the PCBs to create repro's of Super Mario World romhacks for some friends (including the creators of those hacks).

They are 32Mb ROMs, so I'll be foregoing the bank select switch and installing wire links in R1-R4 to fix everything in place, and use the whole 27C322.

When choosing the components, I consulted the datasheets and found that the FM1808 can be substituted for the FM1808B or FM18W08, both of which seem to be more readily available on AliExpress.

The FM18W08 in particular seems to be everywhere, and it's simply the wide-voltage variant if the FM1808, which supports lower voltages with looser timings. At 5v, the timings are identical to the FM1808.

Anyway wish me luck! The PCBs should arrive in the next few days, pretty exciting!
Hey, sorry for the pin 20 issue, this one really escaped me, but really easy to fix as you said.

Glad to hear you're going to build some carts! If you can give me some feedback I would appreciate, also if you find any dificulties or any problem don't be afraid to ask! I'll help as I can.

The FM1808 variants should really be fine, don't worry about them, buy the ones that you can find.

Pretty exciting indeed, I'm eager to hear back from you when they arrive!
RetroSwim
Posts: 11
Joined: Tue Mar 09, 2021 4:09 am

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by RetroSwim »

Absolutely, I'll post pics and stuff when everything's done! :)
DeLFuS
Posts: 6
Joined: Tue Feb 23, 2021 1:33 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by DeLFuS »

Hello! I have sent to make some test plates to build. The truth is that the FM1808B is very expensive to get and the FM1808 is going up in price. In the end I have found the latter at an affordable price and bought them. What differences do these two have with the FM18W08? Is it necessary to make some kind of modification on the plate?

Image
soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

DeLFuS wrote: Wed Mar 10, 2021 12:57 am Hello! I have sent to make some test plates to build. The truth is that the FM1808B is very expensive to get and the FM1808 is going up in price. In the end I have found the latter at an affordable price and bought them. What differences do these two have with the FM18W08? Is it necessary to make some kind of modification on the plate?

Image
Hey, as said before, variants of the FM1808 as the FM18W08 shouldn't really be a problem, I just didn't test them because I don't have them all.

Glad to see that you're building one too! As I said to RetroSwim, any problems i'm here to help as I can. Also, if you don't mind, could you please give me feedback after they arrive and you test them? Its good for making improvements to the project as needed, the more people testing better!
RetroSwim
Posts: 11
Joined: Tue Mar 09, 2021 4:09 am

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by RetroSwim »

First a suggestion for the design, I reckon make pin 1 more obvious. On the back you put the U5/U6 designators at the Pin 1 ends, but on the other side it's inconsistent between the RAM and the logic ICs.

Anyhow... It's not working! D:

Just a black screen. Other than checking my soldering, is there something to do with the ROM splitting that I need to do differently? Byte swapping or anything like that? I assembled everything but the flash memory, including the wire link from U5 Pin 20 to +5v.


In term of the ROMs themselves...

I removed the header and verified the checksums, all that seems to be in order.

The bytes seem to be swapped when viewed in XGPro, is this expected?

Image

I suspected my ROMs (they are 32Mbit SMW hacks, maybe something peculiar about them), so I tried writing a dump of my SMW cartridge, and still no joy.

I'm using one of those adaptors that lets you write the 32Mbit ROM in 4MB chunks on a TL866-2.

What should I try next?
soniccd123
Posts: 46
Joined: Sat Jun 27, 2020 12:01 pm

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by soniccd123 »

RetroSwim wrote: Mon Mar 15, 2021 5:42 am First a suggestion for the design, I reckon make pin 1 more obvious. On the back you put the U5/U6 designators at the Pin 1 ends, but on the other side it's inconsistent between the RAM and the logic ICs.

Anyhow... It's not working! D:

Just a black screen. Other than checking my soldering, is there something to do with the ROM splitting that I need to do differently? Byte swapping or anything like that? I assembled everything but the flash memory, including the wire link from U5 Pin 20 to +5v.


In term of the ROMs themselves...

I removed the header and verified the checksums, all that seems to be in order.

The bytes seem to be swapped when viewed in XGPro, is this expected?

Image

I suspected my ROMs (they are 32Mbit SMW hacks, maybe something peculiar about them), so I tried writing a dump of my SMW cartridge, and still no joy.

I'm using one of those adaptors that lets you write the 32Mbit ROM in 4MB chunks on a TL866-2.

What should I try next?
Hey,

Swap the ROM bytes before writting to the EPROM, this may be the cause of the problem. May need to add this information on the project page.

Also check the jumpers if they're set accordingly, if just one is incorrect it may not work.

Gonna take a look at the designators, thanks for pointing out!

Hope this helps.
RetroSwim
Posts: 11
Joined: Tue Mar 09, 2021 4:09 am

Re: Open Hardware SNES Repro PCB with FeRAM support

Post by RetroSwim »

I'll try byteswapping before writing. Cheers.

Maybe a broader summary of your process for preparing+writing the ROMs would help?

SMW is a LoROM, and I definitely have all the jumpers set to L, that was the first thing I assumed I'd stuff up :lol:
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