Emulation Dumping Download Play titles

[shinji257]

So just for clarification I'm not looking to locate. What I want to do is properly extract the Download Play rom out of a full cartridge. For context the rom is a pairing of a BCN file and a NDS file. I can get the NDS file easy enough. That actually matches up with dat listings I've checked. However I've only been able to get a generic dummy BCN file and I must be missing something that is preventing me from getting that properly.

Steps taken so far.
* Extract data from original rom image using ndstool (v2.1.0 in case it matters)
* locate SRL file within the data structure
* Change extension to NDS
* Run DSDLP Assembler (v1.0) against NDS file. It fixes the NDS and gives a BCN but it's wrong.

I think I'm missing a step somewhere but I don't know what it is yet. Can anyone provide any insight to this?

 

[FAST6191]

It is not always srl (assuming you mean extension, if you mean format then yeah), many times it is utility.bin (usually within a dwc directory) and there have been a few other options besides. The download play ROMs go one further but injection into those and bothering of them is covered elsewhere.

As you say they are slightly malformed (or indeed probably properly formed for their purposes, most evident usually being size values say they are very large where reality is rather different) .nds files and can be pulled apart the same way (the thing many want them for -- either standalone data or as probably additionally compressed but simplified clues to the formats of the main game -- very few people have ever really bothered to hack them as flash carts were so ubiquitous that normal multiplayer, be it wifi or multicart local, was the preferable route* and flashme was also not very popular once DS slot carts took off, it would also be very very late in the day when the signing bugs were discovered that obviate that).

I am not terribly familiar with the BCN aspect (short for beacon, what your DS likely got when you put it in download play seeking mode). Indeed if it is not contained within the utility.bin or .srl or whatever then I would probably go manual or look for an indicator (the format and data formats are similar enough that absent any compression you can probably search for an aspect as you might with more conventional banner data) and search for that, or hope the debuggers work well enough that you can find it being searched for in addition to/prior to whatever sends the utility.bin (whether watching for ROM reads or watching the otherwise unused wifi aspects being one of those dealer's choice things).

*I know some games have quite different gameplay variants between wifi (if any, many but not all things being still playable with savedswifi), local mutlicart multiplayer (not always the best compared to wifi offerings) and download play options. Advance wars usually being a major discussion point in this (normal multiplayer vs an odd RTS thing), mario kart (though most of that is people wanting to play as dry bones in normal efforts or not play as dry bones in that, or do beta/custom tracks in the download play versions). If the otherwise silent readers of a fairly technical thread want to note their favourite or create a new thread for such things I am up for that.

 

[shinji257]

I figured out how to use melonDS to do it and what I was missing there. You have to pause emulation right when the Nintendo logo comes up and before the game actually boots. From there just set the name to "Nickname" and now I'm getting CRC32 matching BCN files. Now to fill those MIAs. Thank you for responding.