melonDS-emu
Local Communications with other official DS
I wanted melonDS to connect with other official Nintendo DS using Local Communications, please.
to clarify on this
it's actually something that piques my interest, because of the technical challenge aspect and how cool it'd be if it worked
but the main issue is syncing
basically, melonDS doesn't run things at the same smooth, uniform rate as a DS
during local multiplayer comm, there's a whole sync mechanism that ensures things work well. basically, the host instance can tell client instances "run up to this point, then wait for a wifi frame".
but obviously, we have no control over an actual DS, we can't tell it to wait for us...
there's that, plus inherent latency due to running on a multitasking OS, going through drivers, etc.
I know that in general, games send one CMD frame per video frame during gameplay, but they send more when transferring data. Pictochat is also different in that it sends one CMD frame every 4ms.
the tricky part is that when a CMD frame is received, there is a very specific (and tight) window to send a reply. in practice, DS software handles it by having a reply frame ready in advance... then melonDS does what it takes to make the game happy (provided frames are received in time). so there could be some leeway there...
though, it would require a specific type of adapter.
the operation of DS local multiplayer seems to be based on 802.11 PCF, but I don't know how much of it is standard... there's probably a lot of stuff about the 802.11 standard that melonDS doesn't implement properly, too.