allow dumping of firmware from is-nitro units

[Mythra]

the is-nitro-emulator/is-nitro-debugger units are development kits for the original ds, and dslite. unfortunately, there is no readily easy way to run a flashcart on them (as they use their own debug signing keys), and even for those of us with ds development cartridges we can write too, libnds does not support writing to these expectedly. as a result before this PR it was impossible to actually get the dump from this tool. the dumping techincally succeeds we just have nowhere to write the file.

at first i tried playing with getting it to dump over a network, but the hardwired connection didn't seem to be supported by libnds, and the wifi connection i couldn't get to trigger either (not to mention wireless connections that folks can use with these consoles are greatly dwindling due to no WPA/WPA2 being allowed). so i gave up with that.

luckily though, even though we don't have a filesystem to write too, and we don't have a network connection, because this is a development kit we have the ability to dump the memory from these devices while they're running. this means we can techincally use RAM as a filesystem to dump memory from. we do have enough memory to store the dumps one at a time without issue. so instead of writing a file, we just allocate a chunk of memory, write easily searchable/findable identifiers, and wait for a human/process to dump the files out of memory onto a computer that does have a filesystem, and can continue on.

for a human to replicate this with an is-nitro-debugger you can:

• rename the built nds to srl.
• load it up through nitro-debugger on the pc, and continue with the dump until you see your first memory address.
• using the debugger application, use the memory dump tools present to write the memory to disk. Cut off the beginning DE, and ending AD's, and save the file. validate the CRCs match, and press start to continue. repeat for each file til your done.

i've also written a tool that can automate the dumping, and requires no human input past the first "yes run in dev-kit mode", that uses @GerbilSoft's ortin: https://github.com/GerbilSoft/ortin , to completely automate the process. it scans memory for our identifiers automatically, and then writes an identifier back to tell the application to automatically continue.

[lifehackerhansol]

It'd be interesting if you could write a routine to write to a dev cart. Though not that important, since as you say one can just dump the mem and call it a day.

Do you know if there is any noticeable way to check for IS-NITRO during runtime (such as deviceType in firmware_header_t)?

[Mythra]

@lifehackerhansol I didn't think you could write to the devcart while the device was in emulation mode, but I do have a cart, I'd certainly be happy to poke around, and see if I can get it to work (I have not spent a bunch of time with my nitro unit unfortunately).

As for noticeable way to check, I don't believe so? The device type is just DEVICE_TYPE_NDSP_PROTO (aka 0). Which I think is shared with other prototypes? I will also admit I haven't spent a ton of time looking into the different firmwares though. If it's helpful, here's the screen from when I just commented out the filesystem accesses:

If it's also helpful: https://archive.org/details/is-nitro-emulator-firmware-dump is the firmware dumps I took myself following the strategy above.

[lifehackerhansol]

You're right, so not something we can properly verify. That's fine.

As for the dev cart... maybe if you abuse the NAND saving functionality (iirc they can save to real carts)? Not 100% sure. I don't expect everybody to have one of these though, so likely not worth dealing with it here.

[Mythra]

Yeah I didn't think nitro units could write save data normally (I know when running through the debug tooling it certainly doesn't work), looks like some sources though claim it should be possible:

If your ROM requires backup hardware (game save info), you will need to insert a dev card with the right type of save memory (EEPROM vs flash, and right size). From the PC software you can then click the toolbar button "Turning the power on/off of the DS card slot", which will turn on SLOT-1. "SYSTEM1" LED should turn on to indicate SLOT-1 is on.