Nintendo DS Emulator - DSEmu

17 January 2006: DSEmu 0.4.10 is out with bugfixes and new functionality! Sprites and some 8 but pallette based bitmap modes are working! Many more demos run. Check out the working examples or download them from your favourite homebrew site. Keep an eye on my DS Developer weblog for more information.
21 December 2005: DSEmu 0.4.9 is out. This version contains mainly bug fixes and changes to get it working with devkitpro r17 and libnds dated 2005-12-12. I've also added a section to this page with links to some working examples to try with DSEmu. Keep an eye on my DS Developer weblog for more information.

• Overview
• Screenshots
• Download
• Examples that work
• History
• Source Code Repository

DSEmu is an open source Nintendo DS Emulator written by Imran Nazar and released under the BSD License. Unfortunately Imran hasn't been able to continue development of it and on the DSEmu forums he welcomed other people adding to it.

Although DSEmu is not very complete it does have at least two things going for it. The first is the source is available. And the second is it has a debugger and stepper built in. So you can step through the ARM7 and ARM9 disassembly which is quite useful.

I got the latest source and made a few changes to get it working with some demo programs. It has quite a few limitations still but being able to step through the code, examine the ARM registers, etc has prove quite educational to me. I've made that release, with source, available here for anyone who wants to use it.

Other Nintendo DS emulators are Dualis and IDeaS.

Screenshots

WinDS	Ruby
Tickle Girl 1	Tickle Girl 2
Space Invaders	Battleships
Python Power	YASFCave
Mode 5 Scrolling Demo	TicTacToe

This is a list of some quick example homebrew programs that I've tested and work with DSEmu. This should give you something to quickly try. Other examples that may or may not work can be found on my tutorials pages or some of the Nintendo DS homebrew sites. Don't forget to unzip the file to extract the .nds which is what should be loaded into DSEmu.

• WinDS (~500Kb)
• YASFcave (~100Kb)
• Ruby (~15Mb)
• Tickle Girl (~13Mb)
• Devkitpro Sprite Bitmap Example (~39Kb)
• cassebrique (~1.1Mb)
• birds (~100Kb)

• VRAM mapping is more correctly emulated. Demo's that didn't correctly show both screens should start working now. Most notably this allowed WinDS and Teenage Queen to work.
• Various bug fixes to solve crashing problems.
• Fixes to enable console text to display with DevkitPro r15 compiled applications. Unforunately this fix breaks console text displayed by applications compiled with earlier versions of DevkitPro. If you wish to run these applications in the meantime I suggest using DSEmu 0.4.5. I hope to have this resolved in the next release.
• SRAM support contributed by Ryo Sazaki. This adds a new file menu allowing saving the contents of SRAM and loading data into SRAM. As an example, the SRAM tutorial now works.
• A log window has been contributed by Troy Davis. Using 'View/Log' in the menu will display it. When using the debug SWI 0xFF the message will be displayed in the log window.
• Some of the code was cleaned up by Julien Hamaide so the number of compiler warnings is reduced. Julien also fixed a problem with the square root SWI.
• Unfortunately a problem has surfaced with a few demos crashing that did not crash in previous releases. Strangly these happen only in the release version of DSEmu 0.4.6. If you build a debug version from source they run fine. I hope to have this fixed in the next release.

0.4.5 has the following changes from 0.4.4:

• IPCSYNC register has been partially implemented. It works except for interrupt support. This allows the E3 commercial download demos to boot a bit further along. Unfortunately they don't actually run yet.
• Extra logging added to CP15 functions to show where memory regions were assigned and with what protections.
• Lots of ARM9 instruction fixes which allowed DSLinux to finally boot. It fails mounting the root partition but is much further along than previous versions.
• Re-enabled some optimisations that were left disabled in 0.4.4.
• Partial implementation of extended rotation backgrounds. Those demo's using mode 5 should start to work now. No support for scaling, rotating or shearing yet though.
• Implemented scrolling for extended rotation backgrounds.
• Added SWI 0xFF for debugging purposes. Calling this SWI with R0 set to a null terminated string will print that string to the log file. Modelled after the functionality in Dualis. Note that SWI 0xFF crashes on hardware.

0.4.4 has the following changes from 0.4.3:

• Implemented coprocessor 15 ability to switch ARM9 vector execution address from 0xffff0000 to 0x00000000. Required for DSLinux to work. Unfortunately DSLinux still doesn't run under DSEmu but it's a step on the way.
• Fixed implementation of ARM opcodes that used suffix 'S'. These weren't dealing with the spsr and cpsr correctly.
• Implemented timers 0, 1, 2 and 3 and attempted to get them running at approximately the right rate.
• Got keyboard interrupts working. Tutorial eight now works in DSEmu.
• Implemented coprocessor 15 ability to switch the ARM9 into low power mode.
• Changed SWI 4 and SWI 5 implementation to use coprocessor 15's instruction to switch into low power mode, and implemented in ARM assembly in the fake ARM9 BIOS instead of C. This works much more like the actual DS hardware now. Previously SWI 4 and 5 only really worked for the vertical blank interrupt, now it works for all interrupts.
• Fixed some timing issues with interrupts and low power mode.

0.4.3 has the following fixes from 0.4.2:

• The Delay SWI has been implemented.
• The POWER_CR register is now seperated into one for the ARM7 and one for the ARM9.
• A workaround has been implemented so ndslib console text displays correctly as well as some tile demos working ok. In 0.4.2 the latter was broken.
• A fix to VRAM mapping.
• The second screen did not work in 0.4.2. This has been fixed. Both screens should work now.
• The screens were often flipped compared to how they worked on hardware. This should be fixed.
• Responsiveness of the GUI has been improved for those demo's that enter 'busy loops'.
• Touchscreen has been re-implemented by implementing parts of the Serial Periphiral Interface (registers SERIAL_CR and SERIAL_DATA). This should mean that demo's using IPC v1 or IPC v2 work fine without having to hard code the IPC structure into DSEmu. This will require tweaks to get working right as I've done the minimum needed to get ndslib demo's working.
• The touchscreen bit of XKEYS now works. Programs can detect whether the screen is touched or not.
• Some logging data removed which was impacting performance.

0.4.2 has the following changes from 0.4.1:

• The interrupt registers have been split so a seperate register is kept for the ARM7 and ARM9. Even though they have the same register address, each CPU actually has a different register. This affects IME, IE and IF. Interrupts were pretty much broken in the previous version of DSEmu without this fix.
• Added the 'ARM7 specific IWRAM' memory area from 0x03800000 with a size of 64K. Thanks to DSTek for providing this information. Previously only the 32K Shared IWRAM area at 0x03000000 was implemented and ARM7 binaries greater than 32K were crashing the emulator as well as trashing the shared IWRAM.
• A few signed/unsigned comparision issues was causing the emulator to enter infinite loops.
• The VCOUNT register is now a single register rather than having one per lcd screen. Demo's that checked for the VCOUNT being in the VBlank area would hang due to this never being updated. Unfortunately these demo's still run very very slowly due to the 'busy loop' polling this register. I hope to have this fixed in the next release.
• The SWI values were wrong in the switch statement that handled these calls. This resulted in the wrong SWI call being made. The main result of this was the ARM7 code would do a 'halt' instead of an SWI Delay which meant any ndslib based code would have no ARM7 support.
• Fixed a problem with ARM7 interrupts meaning most IRQ code should work fine now.
• ndslib Console output would display incorrect characters. This has been fixed.
• With the exception of Space Invaders, all my demo programs run under this version of the emulator in some form or another. Sound doesn't play but the touch screen values are updated and directional keys are processed, etc.
• Using 'animated step' in the debugger now updates the display. Previously no graphics would be displayed while stepping.
• Using 'debug run', followed by pausing, then stepping, would not work. The stepper would be broken from then on. Fixed.

0.4.1 has the following changes from 0.4.0:

• A more correct ARM9 bios interrupt routine is used, avoiding the hack that I put in place previously where one of the registers loads was hard coded in the ARM9 evaluator.
• The interrupt waiting SWI routine was using an incorrect register so the return from the wait was not reliable.
• Bugs related to switching between ARM and Thumb mode, and restoration of the spsr from the cpsr at the end of an interrupt were fixed.
• The interrupt handler expected the handler to be ARM code not Thumb code. The libnds handler is in Thumb so fixed code that was previously there but not working to execute Thumb code if the code is indeed thumb.
• Implemented some of the ARM9 Coprocessor instructions for DTCM and ITCM handling (specifically registers 6 and 9).

The source for DSEmu is in a Darcs archive. Using Darcs you can retrieve the latest code with:

darcs get http://www.dsdeveloper.co.nz/repos/dsemu

This will create a 'dsemu' directory containing the latest code. Darcs is a great version control system. To get the latest changes to the repository use the 'pull' command:

darcs pull http://www.dsdeveloper.co.nz/repos/dsemu

Each local copy that you've retrieved is a fully fledged repository. You can record changes, pass them to other repositories or send them to me as patches. Here's some common commands:

; Record changes you've made to your local copy into a patch
darcs record

; See what changes you've made that haven't been recorded yet
darcs whatsnew

; See just a summary
darcs whatsnew --summary

; Add a new file
darcs add newfile.txt

; Create a patch file containing changes you've recorded to
; email to me.
darcs send -o patches.pat http://www.dsdeveloper.co.nz/repos/dsemu

Feel free to work on the source and send me patches using the 'darcs send' command shown above. I'll integrate them into the central repository.

News and updates to this software can be obtained from: http://www.dsdeveloper.co.nz.

Copyright (c) 2006, Chris Double. All Rights Reserved.