CAUTION: Backup your eMMC before installation. Pick a tested/stable unlaunch version (unless you have a hardmod for easy unbricking). Unlaunch modifies bootfiles - if installation goes wrong and you can neither boot the original firmware nor bootcode.dsi from SD card, then you'll need a hardmod to re-install your eMMC backup copy.
Donations would be very welcome. Unlaunch started as a quick 3 weeks hack, barely allowing to 'boot something'. That 3 weeks quickly turned into 3 months, and unlaunch has now envolved to a complete firmware replacement, fully supporting all those complicated hardware initializations needed to access things like wifi, sound, ram, and touchscreen hardware.
Concerning donations, I've got a little money that might pay off for the first 1-2 weeks, but it doesn't remotely cover the 3 months (and certainly not the preceeding 4-5 years that I had spent on DSi reverse-engineering), and even without special expenses, paying for food & rent can be often troublesome.
So, if you can share a few dollars - you would be welcome to share whatever you have!
Before Installation - make a backup
Make a backup of your eMMC chip. If you have a DSiware exploit, use the "Backup DSi NAND" function in fwtool.nds, for example. With hardmod, just dump the eMMC chip. Either way, backup the unmodified file in a safe place, you can use it to restore the console to working state if something goes wrong (if the console gets totally bricked then you'll need a hardmod to do this).
The eMMC contains some console-specific files with RSA signatures - if that files get lost then you've a problem - there is no way to replace them by using equivalent files from another console.
Automatic Installation (requires a working DSiware exploit)
Installation is easy if you have a console with Flipnote installed (the game came pre-installed on many consoles, and it was also available as free download when the DSi shop was still online). However, some people may have deleted or missed downloading it, and it wasn't released in CHN/KOR regions. Anyways, if you have flipnote, use this exploit:
Manual Installation (via hardmod)
This requires soldering four wires to DSi mainboard (eMMC signals CLK, CMD, DATA0, GND), attach the wires to a SD/MMC card reader, and use some tool like HxD or Win32diskimager to dump the eMMC content to a 240Mbyte file.
Next, you will need the CID and Console ID for decrypting the eMMC image. There are several to obtain that values, and it's also possible to brute-force one (or both) values.
The bootcode.dsi (and bootthis.dsi) can be general nds/dsi files of following type:
Unlaunch supports SD/SDHC cards (max 32GB, preformatted as FAT16/FAT32). SDXC cards (above 32GB, preformatted as ExFAT) are not supported, neither by Unlaunch, nor by DSiware in general.
Reformatting SD/SDHC cards isn't recommended, or it should be done only with dedicated SD card formatting tools (that maintain cluster size matched to physical sector size). However, reformatting SDXC cards may help to get rid of the weird ExFAT format.
I would be glad to receive any non-working SD/MMC cards, so I could either support them or at least add some meaningful error message for such cards.
Feedback / Contact
I haven't received too much feedback from too many people. I assume that a bunch of people are discussing unlaunch in chatrooms, without telling anybody else about their findings (although Apache Thunder seems to have forwarded some of that info to me, thanks there). Some people also published info about suspected unlaunch bugs on random webpages, but without giving any details on how to reproduce that bugs. Apart from bug reports, testing would be also interesting. Like knowing if DSi browser can be already booted as bootcode.dsi and bootcode.prv (if somebody can spare 5 minutes on that so I won't need to test it myself).
Official forum thread is in nesdev / other retro dev forum. You can also reach me per email email.
How it works
Bootstage 2 is loading the launcher's "title.tmd" file to memory, and it's doing that without any error checking for "filesize>limit" (instead, it's only doing a rather surreal "filesize>filesize" check). The defunct error checking is allowing to load about 80Kbytes of useful code to Main RAM and to overwrite a task switching structure, which is then causing ARM9 to execute the loaded code, and which can then tweak ARM7 to execute custom code by remapping some portions of shared WRAM.
Yup, it's actually that simple. The bigger problem has been to find this exploit within the 400,000 lines of code that bootstages 2 and 3 consist of (hence taking almost 10 years until somebody found a bootcode exploit).
The other issue is that bypassing the original firmware is leaving most of the hardware uninitialized (the DSi is often said not to have an operating system - which is true - but people tend to forget that things like wifi, wram, sound, touchscreen, and system variables won't work without extensive firmware initializations (not too mention booting nds/dsi titles from sd/mmc or cartridge slot also needing extensive loading and decryption functions).
That initialization stuff isn't exactly easy. It did help that I had already reproduced most of it when making no$gba in the past some years. As of unlaunch v1.0, I am quite confident that I got the firmware replacement working quite well - and that DSi consoles are now booting up ways faster than with original firmware.
The thing still missing would be a bootmenu for selecting titles from sd/mmc, though devrs will more likely stick with loading wifiboot/dslink directly from sdcard, so a bootmenu won't be of too much use (except maybe for gamers).
Normally, I am avoiding to make bloated up software. In this case, triggering the exploit needed the file to be padded to a hefty size of 80 kbytes - so I have filled parts of that space by adding some background gif's, roughly themed around crashes or launch failures...
The images are showing Herzogin Cecilie. I've also considered Principessa Jolanda for actual launch failures, and the Skyluck for intentionally grounded vessels. But then, the photo with the half sunken ship's figurehead nearly kissing the waves is so strong that I've chosen that one (not to mention that I like the way how the lower image is mirroring the lines from the upper image).
Some people appear to be scared about the background images. Be aware that the images will be displayed as boot message in place of the healthsafety screen (unless you know how to store a working bootcode.dsi file on SD card).
v1.3 09 Aug 2018 - forces disabled cache to be MADE EMPTY before starting loaded title - rearranged init sequence for loaded titles and added more cache flushes - moved scfg state from 380FFCX to 3FFFFCX, passes final state to loaded title - bugfix: skip wifi init by button Y (not button B, which is ROM cart loading) - checks for unknown cid/csd AFTER manually reading cid/csd from hardware v1.2 05 Aug 2018 - rom loader: variable ARM9 secure area size=4000h..1000h, or skips if none - zerofills vram/oam/palette before starting other titles (takes about 6ms) - arm7_copy_scfg_state_to_ram_and_wram (passes SCFG_OP to ARM9 side) - supports twl-debugger (with 80h-byte address shift, without region patches) - removed forced SFCG_EXT.bit31=1 patches (since they weren't too useful) - fixed color-flash on patch errors, resumes further patches after keystroke - added wildcard for anti-black-fill patch (did hang firm v1.4.5 since v0.9) - moved unknown camera/emmc warnings after dsi-mode check, ie. not in nds-mode - removed warning on unknown CID/CSD for ST NAND02GAH0LZC5 eMMC chips v1.1 25 Jul 2018 - removed warning on unknown CSD for KLM5617EFW-B301 eMMC chips v1.0 24 Jul 2018 - co-releases: no$gba v2.9a and wifiboot v2.2 - webpage: new unlaunch.htm page, with more installation info, new forum, etc. - speedup: uses DMA for SD/MMC-read, SDIO-write, and AES-read/write, ROM read - rearranged EXMEMCNT init, ensures ARM9 IPC IRQ enabled before waiting for it - installer: uses fill_copy_list (instead of relying on carthdr copy in ram) - installer: stores no$gba footer at eMMC offset FF800h (if it's zerofilled) - installer: omits FAT writing if FAT unchanged (as so on unlaunch updating) - installer: disables BPTWL powerbutton auto-reset during install_now - sdmmc/sdio: removed pre-wait and soft-timeouts, instead checks hw error bits - initializes SOUNDBIAS (maybe better in case games don't do that themselves) - moved GIFs to separate non-lz77 memory block (avoid double compression) - verifies camera chip id and emmc cid/csd with warning if unknown hardware - added Y button hotkey: load NDS/DSi title from ROM-cartridge slot - rom loader: cartpower, romctrl, 4004012h/14h, load chip id and secure areas - rom speedup: uses 1000h-byte blocksize for faster 1t-rom loading - rom speedup: forces fast mrom timings for mrom carts with wrong cart header - rom speedup: forces less slow 1t-rom timings for actual 1t-rom carts - rom speedup: forces reduced secure area delay of 8ms for 1t-rom carts - rom speedup: uses slot-swap-reset-trick (instead slow power-off/on) - rom speedup: crops hardcoded cart power-on delays to 1ms/1ms/0ms/1ms - more accurate modcrypt (old was overcomplicated, and bugged on size=0) - supports place_aes_keys (maybe needed for jpg/camera or verdata stuff) - sets POSTFLG register (needed for NDS titles like EragonDemo, DownloadPlay) - moved twlcfg/wlfirm/hwinfo elsewhere (reloc to 2000400h only for DSi titles) - resumes default BPTWL powerbutton mode (unless when booting nds-titles) - enter_nds_mode: reloc 2FFFxxxh to 23FFxxxh, set 4MB-RAM, NDS-ROM, ARM9 67MHz - enter_nds_mode: set NDS-TSC-touchscr mode, init NDS-Wifi, NDS-SNDEXCNT v0.9 14 Jun 2018 - co-releases: no$gba v2.9 and wifiboot v2.1 - creates device list in ram (with names sdmc:/bootcode/bootthis.dsi/pub/prv) - uses lz77 compressed arm9 code to squeeze all new features into 80kbyte file - moved gif decoder buffer to address not conflicting with cart loader - loads TWLCFG0.dat, HWINFO_S.dat, and HWINFO_N.dat to main ram structures - added touchscreen/sound controller init (required for working sound output) - new patch: prevent original launcher from black-filling engine-a-palette - proper cache init/initback with cleaning dirty lines before invalidating - supports blowfish/secure_area (requires rom/itcm) and modcrypted dsi areas - loader: applies cartheader MBK values for entry and for arm7/arm9 loading - loader: applies cartheader WRAMBANK and SCFG_EXT7 values before entry - added hotkey: hold button X to load "bootthis.dsi" instead of "bootcode.dsi" - removed patch supported languages (caused touchscreen issues in korea/japan) - initializes wifi related hardware (rtc.fout, bptwl[30h], gpio_wifi) - uploads wifi firmware before starting bootcode.dsi (cmd5/upload/init/wmi) v0.8 10 May 2018 - added one more patch wildcard for firmware v1.4.5E v0.7 08 May 2018 - write-protects ALL files/folders in launcher content folder (xcept . and ..) - added hotkey: hold button A to skip bootcode.dsi (and force normal launcher) - installer: moved arm7entry from 37f8000h to 2380000h (better for 4swordhax?) - when starting bootcode.dsi: skips GIF display, keeps I2C warmboot flag - added more patches to launcher (rsa) and bootcode (gif instead whitescreen) - rebuilds whole eMMC Info at 2FFD7BCh (in case destroyed by some exploit) - uses faster 4bit sdmmc mode (if detected/supported) - more specific error messages for fat mismatch, bad mbr/vbr, etc - skips DSi DISPSTAT wait when (trying to) run in NDS mode v0.6 24 Apr 2018 - write-protects .tmd file (prevent Data Managment from deleting it) v0.5 23 Apr 2018 - first public release (installer, gui, loader for bootcode.dsi) v000 01 Apr 2018 - discovered exploitable .tmd filesize in bootcode disassembly