melonDS aims at providing fast and accurate Nintendo DS emulation. While it is still a work in progress, it has a pretty solid set of features:

• Nearly complete core (CPU, video, audio, ...)
• OpenGL renderer, 3D upscaling
• RTC, microphone, lid close/open
• Joystick support
• Savestates
• Various display position/sizing/rotation modes
• (WIP) Wifi: local multiplayer, online connectivity
• and more are planned!









Download melonDS

If you're running into trouble: Howto/FAQ

If you're feeling generous: melonDS Patreon
Sorry for the silence lately
I know that since the 0.9 release, there hasn't been a lot of progress. On my side, things have been pretty rough, especially regarding depression. Under these circumstances, it's good to take a break.

Anyway, what can we attempt doing, at this point?

Besides dealing with the pull requests and issue reports?

One thing I was working on lately was DSi camera support, but I didn't get too far. I'm going to need hardware tests to figure out how the camera hardware works. Considering the lenghty initialization procedure for those, it's not quite something I look forward to. So I'll post more about this when I get further into it.

I have ideas for the OpenGL renderer, namely, a better method for rendering quads. It would need more work for an implementation though, but might be worth it.

But, one of my main concerns is about wifi, especially local multiplayer.

At this point, melonDS is mainly known as 'the wifi emulator'. It's a bit sad that, 3 years after we got it working, we're still telling people to disable their framerate limiter and pray. We can probably do better.

It's not like we haven't tried, though. You might have seen that branch named 'betterer_wifi' in the repo. I was hoping to run the wifi with more stable timing, but it was a trainwreck, it performed even worse than our current method.

The main issue with local multiplayer is that it requires tight synchronization to function. You might remember how finicky it was back in the old days, you would start lagging and disconnecting as soon as your friend was more than 10m away from you. Long story short, the protocol works by having the host repeatedly poll its clients, multiple times per frame, and each client is given a narrow window to respond (the time given is barely greater than what it takes to transfer the response frame).

... read more
melonDS 0.9 is out!
It's been forever, but, finally, here it is. melonDS 0.9.

And it's big.



So, what are the highlights of this release?


- JIT recompiler

Brought to you by Generic (aka RSDuck), the new JIT recompiler enables melonDS to run much faster, and quite often reach fullspeed even when emulating DSi titles!

There are a few settings you can try out to get the most out of this JIT. While it has been heavily tested and worked on, it's still imperfect.


- DSi emulation

This is the other flagship feature of this release: melonDS now emulates the DSi!

... read more
Getting there...


I'll let you guess ;)
Messin' around with the GL renderer
First of all, lil' status update. Things are nearly ready for the 0.9 release, we are mostly busy ironing out small issues here and there to ensure everything is good. Nobody would want something big like that 0.9 release to end up being a total flop.

Also, if you ever wondered why progress is slow: an emulator project is like a tree in that once you're done with the trunk, it branches off in a billion different directions. At this point, melonDS is too big to be a one-man show. There are a few people working on it now, but there's only so much we can do with our time and motivation.

Anyway, while Generic is busy polishing the JIT, I figured I'd go around and try fixing some of the issues on the issue tracker.

This one, Deformed floor textures in the Celestial Tower (Pokemon Black/White) (OpenGL only), is an interesting problem. The base issue is that, if you happen to remember, the DS can draw quads natively, while modern GPUs can't. Actually, it's even worse: clipping on the DS cuts through polygons but doesn't create more polygons, which means that you can end up with a maximum of 10 vertices per polygon. For example, a triangle that sticks out of the view volume can become a quad, a pentagon, or more.

The base issue here is faulty rendering of these polygons that have more than 3 vertices. The DS employs a scanline-based convex polygon renderer, so it doesn't care how many vertices your polygon has. Software renderers used in DS emulators use similar filling algorithms, so no problem there either. However, when you use OpenGL, it's another deal entirely -- modern OpenGL-compatible GPUs are very good at drawing triangles, but... that's about it.

So, what do you do when you need to render a quad? Easy, split it into two triangles!

Suppose the quad below.



All fine and dandy. Now we split this, like this:

... read more
maxmod fixes
Sorry for the silence lately -- these times are getting pretty busy. melonDS wise, we're trying to perfect the JIT and the few other things we want for the 0.9 release. Real life wise, on my side, I'm starting the procedure to get my gender marker updated, which is going to be the last big thing for my transition.

Anyway, just yesterday, asie told me that maxmod's interpolated mode was broken in melonDS, which piqued my curiosity.

What's maxmod, you ask? It's a real fancy audio library for the GBA and DS. I don't know much about the GBA side of it, but on the DS, it supports three modes: hardware mode, interpolated mode, and extended mode. Hardware mode is fairly straightforward. Interpolated mode resamples audio on the fly, applying interpolation to make up for the lack of hardware interpolation. Extended mode does its own mixing, adding support for more channels than the hardware can offer.

In our case, interpolated mode was broken, outputting pretty much short high-pitched beeps and nothing else. I was curious to see if maxmod used any of the fancy audio capture/output modes that melonDS doesn't support (because no commercial game uses them, and my policy is to avoid implementing things until I have test cases). melonDS is set to report if any such features are being used, but in this case, it didn't report anything out of the ordinary. So this meant I'd have to dig further.

Quick regression testing showed that interpolated mode worked okay-ish on melonDS versions prior to 0.6. Well, it didn't sound as it should, but it was atleast reasonably close, instead of just being high-pitched beeps.

So apparently it was completely broken when sound FIFOs were implemented. The FIFO logic was fine, but the addition of that feature worsened the consequences of a bug that had always been there.

I logged what was going on during playback, to try and figure out where it failed. It appeared that the data being fed to the audio channels was fine, but, for whatever reason, the channels themselves failed to actually pull the data from memory. More logging revealed some strange things, like how certain things started at zero when they shouldn't. Notably, the channel timers started at zero, when they're supposed to start at the SOUNDxTMR reload value. But also, the FIFO level started at zero, causing it to immediately go negative and break the FIFO filling logic.

For a while, I scratched my head at all that, until it finally clicked.

In interpolated mode, maxmod will first disable the mixer, then sequentially initialize the channel registers, then enable the mixer, letting all channels start in perfect sync.

... read more
hi
I got the surgery. I am alive and well. Thank y'all! :)
The new wifi adventure
I'm doing this while waiting for my surgery, which will be in 3 days. So, a bit more about yesterday's screenshot.


Basically, it all started with a new branch called slirp. What's that, you ask, another of Arisotura's oddball noises?

Nah. If you followed the melonDS history, you know that a while back, support for internet connectivity was added. It was pretty similar to how DeSmuME did it back then: providing a basic emulated access point to connect to, then forwarding outgoing traffic via libpcap.

While it was straightforward, it had its lot of issues: it required installing libpcap (or any Windows equivalent), required admin/root privileges, and, more annoyingly, did not work over wifi connections, as explained here.

Eventually indirect mode (aka LANMAGIC) was developed to get around this. The basic idea was to emulate a local network and use simple BSD sockets to forward outgoing traffic to the host network. The idea was good, but the actual implementation was more or less a pile of hacks that never really worked right.

Enter the slirp branch. Basically, QEMU's libslirp does exactly what LANMAGIC clumsily tried to do.

So I reimplemented indirect mode using that. Took a while to figure out how to use libslirp, as it isn't really documented, but we got there, and it works beautifully.

More notably, this is how we like it. Unlike direct mode, it requires no setup, it Just Works™. Over any sort of connection, without any special privileges, ...


Then I got carried away and began implementing features of the DSi's new wifi device. From there, you can see how this ended.

... read more
BAAHAHAHAHAHAHHHH


:)
melonDSi has been merged
melonDSi started last year as that clunky DSi experiment branch. Over time, it became more capable, but it still felt really crusty. It was basically stuck in DSi mode, hardcoded all around, didn't work that well, and was based off what became an increasingly obsolete version of melonDS as it was put on the backburner in favor of other fronts.

But that is past now.

I wanted to get it ready for the JIT merge, so I set to work. First off was merging recent melonDS into it, which went smoothly. It was a great sight to see the DSi menu come to life inside the new Qt UI.

Then, in a couple days, the SD/MMC issues were fixed, such that for example Flipnote can now save without softlocking. I then decided that would be a good base, and cleaned it up. Basically, I de-hardcoded it, allowing it to switch between DS and DSi modes, changing how DSi-mode assets are loaded, all that.

And now, there it is, DSi support is part of the master branch.

Couple notes on this:

* It was reworked to require less files. Namely, aeskeys.bin, initmem7/9.bin and boot2_7/9.bin are no longer required. However, it now requires 'augmented' BIOS dumps, the same ones that NO$GBA requires. I intend to provide an appropriate dumper.

* The location of the BIOS/firmware/NAND files can be configured.

* It is able to run both DSi and DS games from the menu. For some reason, some will fail to load, giving that error screen.

... read more
#BlackLivesMatter
You may be aware of what's going on in USA. I'm not going to go in detail over this, but I'm going to state that I stand with the protesters. For the end of racist policing, for the end of capitalism.


Other than that, little status update on melonDS. We're going to merge the JIT branch for 0.9. I figured that it would be easier to merge the DSi branch first, so I've been updating it. I'm going to clean it up some and fix a few things to make it good for a release.

The Qt UI is also nearly complete. All that remains to be done is the cheat interface and taking care of VSync. The other issues have been solved, including the one where the final executable required 25 DLLs -- by using the qt5-static package for MSYS2, I managed to get it down to a standalone executable that is about 21MB in size.