Savestates

[3DSchuminator]

Hello. First of all thank you for the wonderful project, I use it almost every evening. It's nice to play on a game console that I soldered myself ;) I saw in other forks of picoinfones that some people implemented savestates. But their projects have certain limitations. For example, the lack of sound over HDMI, image output to VGA or versions for software composite. I really like your version of the emulator. And now these cover art and descriptions for the games. Delicious! But there is a real lack of full-fledged savestates. If there is no way to make a simple menu with a call by Select + Start with the following options: 1 - Save State; 2 - Load State; 3- Exit to games list; 4 - Return to game. Then maybe at least hang one savestate on a hotkeys?

[fhoedemakers]

Thank you!

Can you give me the links to the forks that implement this savestates. Then i can take a look at it and see if it is possible.

[3DSchuminator]

Thanks for the quick reply! https://github.com/DnCraptor/pico-nes/tree/main first example I found. Save states are easy to make. You essentially need to save RAM + registers and some other hardware states.

[fhoedemakers]

Thanks! Will take a look. Have some other things todo first, but will certainly come back to this.

[fhoedemakers]

#140

[fhoedemakers]

Hi,
I made some progress with savestates. Mapper 0 and 4 are already working.
Are you willing to do some beta-testing? I can send you a test build probably this weekend. I’m concentrating on RP2350 right now (Pico 2), hope to get it also working on RP2040 (Pico). Memory is a constraint here.
Can you tell me the config you are using?

Thanks

[3DSchuminator]

Hello. This is just great news! I'm very glad that you agreed to implement savestates. Of course, I'll be happy to test it. I don't have 2350 boards, I have more than 100 2040s lying around here and there, that's why I try to make devices based on them until they run out :). I developed this console, mostly to assemble it with my child. I didn't make the board specifically so that I could test firmwares from different projects, with different pinouts. That's why I can reconfigure it for any configuration, as long as it's a pure 2040 with HDMI, NES controller and without PSRAM.

You can send test build to 3dschuminator@gmail.com
and I will be happy to test it and provide feedback.

Regards,
Oleksii

[fhoedemakers]

Very cool design you made! Did not realize my project does inspire people so much.

Give me some time to get it working on RP2040.

Thanks

[3DSchuminator]

Thank you! I uploaded my case 3d model here: https://www.thingiverse.com/thing:7077340

[fhoedemakers]

Thanks. Can you tell me which .uf2 you are flashing on this device so i can send you the correct one?

[3DSchuminator]

I think it was Breadboard Pico piconesPlus_AdafruitDVISD_pico_arm.uf2

[fhoedemakers]

Below a test build.

piconesPlus_AdafruitDVISD_pico_arm.zip

Save/Load state is available in-game when pressing SELECT + START Follow the prompts on screen.

When loading a state, the game mostly resumes paused. Press START to continue playing.

Save States should work for mapper 0,1,2,3 and 4 Below the games that use these mappers.

https://nesdir.github.io/mapper1.html
https://nesdir.github.io/mapper2.html
https://nesdir.github.io/mapper3.html
https://nesdir.github.io/mapper4.html

The mapper number is also shown in the Save State screen.

Other mappers can work, but not guaranteed. Please let me know which don't work for you.

[3DSchuminator]

Thank you! I'm currently experiencing severe power outages in Ukraine. But on Monday I'll be able to connect a generator and will definitely test the firmware.

[fhoedemakers]

Oh man, you're from Ukraine, did not realize this. I really hope you're somewhere safe and away from the war zone. The world is a crazy place right now. No worries at all, I can wait. I've attached a version with some bug fixes for the save states. [piconesPlus_AdafruitDVISD_pico_arm.zip](https://github.com/user-attachments/files/23839677/piconesPlus_AdafruitDVISD_pico_arm.zip) All the best, and stay safe!

[3DSchuminator]

Hello. Thank you for your words and for the opportunity to test the new version with save states! I spent half a day today running different games with different mappers. I tested a whole bunch of games on mappers 0, 1, 2, 3, 4, 5, 7, 34, 71, 90. The firmware works stably and I never restarted the console. Great work!
The only bug I was able to find is loading the save in Blades Of Steel. Apparently, some register responsible for the noise channel is not saved/restored there. And after loading, you can hear continuous noise until some other sound interrupts it. But the implementation of the UNROM mapper is not very accurate in this emulator anyway (Bomberman 2 as an example), so it may not be a problem with the savestates. But, just in case, I'm adding a savestate so you can check.
8AB52A24.zip

0-02-05-0852b2e6a4a54f3479fca8ddf31259cd2c0724efd15b06bee7c362deecd45af1_6b1f9f373e4b67fd.mp4

And one more thing. Is it possible to make the save state have the name of the ROM file, as Retroarch does? For example, for the ROM Super_Mario_Bros_(JU).nes, the save file Super_Mario_Bros_(JU)_[0].sav will be created. 0-5 for manual savestates and A for autosave (may be in some future). You can create menu option AUTOSAVE and AUTOLOAD on/off. Then emulator will create/overwrite ...[A].sav on exit and load it on game start.

P.S. Something needs to be done in the future with the accuracy of emulating scanline interrupts. Racing games almost impossible to play, and even in platformers the graphic effects often ruined:

Thank you for your great work and for this project.

Regards,
Oleksii

[fhoedemakers]

Hi,
Thanks for the extensive testing — much appreciated.

I’ll look into the sound issue. Mapper 2, which this ROM uses, doesn’t have any extra runtime variables that need to be saved, so the problem may be in how the APU state is being saved — perhaps it’s incorrect or incomplete.
AutoSAVE/AutoLoad would indeed be a great addition; I’ll look into implementing that as well.

I intentionally used the CRC32 checksum for the save-state filename and path, so the ROM’s actual filename wouldn’t matter. That’s also why I display the checksum and the save-state path after saving. But I guess I could switch to using names like Super_Mario_Bros_(JU)_[0].sav instead of slot0.sta.

Regarding the scanline interrupt: I’m not really an emulator developer — I just ported it and added the extra features. I can make some minor changes, but I’m not sure whether I can pull this part off.

All the best,

Frank

[fhoedemakers]

piconesPlus_AdafruitDVISD_pico_arm.zip
Hi,

Added in-game Quick Save (Select + Button2) and Quick Load (Select + Button1).
Note that Button1 corresponds to B on NES, X on PlayStation, and A on Xbox controller.
Button2 corresponds to A on SNES, Circle on PlayStation, and B on Xbox controller.

Autosave and autoload will be added later.
I also haven’t looked into the Blades of Steel sound issue yet.
For now, the save file and directory names (based on the CRC checksum) remain unchanged.
The checksum is shown in the save-state menu, so it can be written down for later use.

Frank

[fhoedemakers]

piconesPlus_AdafruitDVISD_pico_arm.zip
Hi,
Here’s a more polished build:

• Improved APU state saving (though I’m not entirely sure this fixes the audio issue you mentioned).
• Added In-Game Quick Save (SELECT + Button2) and Quick Load (SELECT + Button1), using slot 5.
• Added Autosave, configurable in the save state menu. When enabled, the game state is saved automatically when exiting to the menu, and automatically loaded when starting the game again.
• Other bugfixes

Note: Save states created with previous versions are no longer compatible, as the state file structure has been updated.

I hope you’ll have time to try it out and share some feedback!

[3DSchuminator]

Hi! I was struggling with some technical difficulties to test the previous build, and you already made a new one! I will definitely test everything tonight! Thanks for the opportunity. I will write a report as soon as I check everything thoroughly.

[3DSchuminator]

I've tested many games, so far everything is fine. I'll continue to test in all modes. From what I've already found:

1. Trying to load an old save from a previous version crashes the emulator after a message about the impossibility of loading the savestate. If you don't have a savestate check before trying to load it, then maybe you should go to the ROM list or reset the emulator. This is better than seeing a black screen with audio glitches in the background.

2. After loading a save from the first level of Bomberman 2, the sound of bomb explosions is somehow fixed. Other sounds are still buggy, but the sound of the bomb is played once, as it should be. Maybe this knowledge will allow you to fix the emulator with its not always correct playback of PCM samples. Maybe this will also help fix Battletoads.

[fhoedemakers]

Hi,

Thanks for testing,

When a state fails to load, the emulator now returns to the rom list.
piconesPlus_AdafruitDVISD_pico_arm.zip

Regarding the buggy sound, an issue has already been filed for this (#111). I’ll see what I can do to address it, though external help may be needed.

Thanks.

[fhoedemakers]

Hi,

I just released v0.34 which among other things include the save state functionality.

Frank

[3DSchuminator]

Nice! Thank you!