Doom 550D

Doom running as a Magic Lantern module on the Canon EOS 550D / Rebel T2i / Kiss X4.

This repository contains the module source and release documentation. It does not contain Doom, Freedoom, or any other WAD data.

Status: experimental. Release v0.4.1 is built for the Canon EOS 550D and is the best playable build tested so far. It is not intended for other cameras.

Watch Doom550D in action

▶ Watch Kick play DOOM on a Canon EOS 550D

⬇ Download the latest Doom550D release

Screenshots

Features

• selectable Doom-family IWADs from the Magic Lantern Games menu;
• persistent debug logging control and safe Doom-log cleanup from that menu;
• up to 32 alphabetically sorted IWAD files in ML/DOOM/;
• separate save slots for every exact WAD filename;
• persistent Doom menu, sound, and music settings;
• low-CPU MUS music with 24 voices, instrument families, envelopes and percussion;
• music mixed with Doom's 8-bit effects into 48 kHz mono camera audio;
• cleanup of input, display, palette, and audio state when Doom exits;
• Canon 550D press/release controls, including held run and strafe modifiers;
• a secret in-game menu for classic cheats, available music and present maps;
• an extra unofficial fullscreen Screen Size setting that renders gameplay at 360x240 and presents each game pixel as an exact 2x2 block at 720x480.

Supported release target

• Canon EOS 550D / Rebel T2i / Kiss X4
• Canon firmware 1.0.9
• Magic Lantern 550D.109 core and 550D_109.sym built from the matching magiclantern_simplified tree
• released module filename: doom.mo

The release binary was built from Magic Lantern base commit 8f8fb3e2f97f156a30da62feeadbfc62244b33bc. Keep autoexec.bin, 550D_109.sym, and doom.mo from compatible builds together. A module built against different exported symbols may fail to load.

No Doom-specific Magic Lantern core modification is required for audio. The required Canon audio stubs are already present in the base commit above. The installed 550D_109.sym must export these symbols:

PowerAudioOutput
SetAudioVolumeOut
SetNextASIFDACBuffer
SetSamplingRate
StartASIFDMADAC
StopASIFDMADAC
audio_configure
beep_playing

If an older Magic Lantern installation does not export all eight names, build and install a matching autoexec.bin and 550D_109.sym before loading the module. Building that ML base with GCC 16 additionally requires the known src/tskmon.c compiler-version guard adjustment; it does not change Doom or the runtime audio implementation.

Do not install this binary on another camera model or firmware version.

Installation

1. Back up the SD card and verify that Magic Lantern works normally.

2. Verify that autoexec.bin and 550D_109.sym come from a compatible Magic Lantern 550D.109 build.

3. Copy the released module to:

   ML/MODULES/doom.mo
   

4. Create ML/DOOM/ or let the module create it.

5. Copy one or more legally obtained Doom-compatible IWAD files into ML/DOOM/.

6. In the Magic Lantern Games menu, select Doom > WAD.

7. Keep Doom > Debug logging set to OFF for normal play. Enable it before reproducing a problem.

8. Restart the camera after changing the selected WAD, then start Doom.

The module creates and manages ML/DOOM/SAVES and ML/DOOM/CONFIG. If no usable IWAD is found, the camera displays a clear message instead of starting the engine.

WAD files are copyrighted game data. They are not included in this repository or its releases.

WAD compatibility

The selector accepts regular .wad files whose first four bytes are IWAD. PWAD level and mod files are not offered as standalone games.

Expected Doom-family IWAD names include:

Filename	Game
doom1.wad	Doom Shareware
doom.wad	Doom / The Ultimate Doom
doom2.wad	Doom II
tnt.wad	Final Doom: TNT Evilution
plutonia.wad	Final Doom: Plutonia Experiment
freedoom1.wad	Freedoom: Phase 1
freedoom2.wad	Freedoom: Phase 2
freedm.wad	FreeDM; primarily useful for multiplayer
hacx.wad	Hacx 1.2; planned, not currently playable

The current selector checks the WAD header, not the complete game format. Heretic, Hexen, Strife, Doom 64, PK3 files, and source-port-specific IWADs are not supported even if a file happens to use an IWAD header.

Hacx 1.2 is recognized by filename, but the current module does not include the DEHACKED parser required for its embedded compatibility patch. It exits at the title loop when D_DM2TTL cannot be remapped to D_HAXTTL. Keep hacx.wad out of the active collection until full DEHACKED support is added.

Download links for freely distributable or commercially available data:

• Freedoom: https://freedoom.github.io/download.html
• Doom + Doom II on Steam: https://store.steampowered.com/app/2280/DOOM_1993/
• Doom + Doom II on GOG: https://www.gog.com/en/game/doom_doom_ii
• Doom Shareware archive: https://www.doomworld.com/idgames/idstuff/doom/doom19s

Controls

Camera control	Doom action
Arrow keys	Move forward/back and turn
Hold zoom in (+)	Run
Hold zoom out (-) + left/right	Strafe left/right
SET	Fire; confirm in menus
PLAY	Use/open doors and switches
Rear wheel	Previous/next owned weapon
DISP. (called INFO internally by Magic Lantern)	Automap; back while in menus
MENU	Open/close the Doom menu
Delete/Trash three times quickly	Open the secret cheat menu; back inside that menu
Q	Confirm the Doom quit dialog

ISO, the depth-of-field button and the shutter buttons are deliberately not used as Doom actions. Canon handles them below the module input layer and can otherwise show EOS overlays, autofocus, or steal the game controls.

Secret cheat menu

During an active single-player level, press Delete/Trash three times within 1.2 seconds. The first two presses deliberately have no visible action. The third opens a paused Doom-style menu with three sections:

• Cheats: activate classic Doom cheat codes and inspect their live state. Toggleable cheats use Doom-style sliders. IDDT cycles through normal map, full map, and map plus objects.
• Music: select music entries that are present in the active IWAD. The current entry is marked PLAYING.
• Level: warp only to maps present in the active IWAD. The current level is marked PLAYING.

Use up/down to select, SET to activate, and left, INFO, MENU, or Delete/Trash to go back. Classic gameplay cheats remain disabled on Nightmare as in Doom; IDDT and level warps retain their original exceptions. The menu performs no SD-card I/O from camera button callbacks.

Display

In Options > Screen Size, move one step right past Doom's standard fullscreen setting to select extra unofficial fullscreen. It renders gameplay at 360x240 and presents each game pixel as an exact 2x2 block on the camera's 720x480 display, without interpolation. The setting can be changed during gameplay.

The status bar is hidden in this setting. Menus, the automap, intermission and finale screens retain Doom's classic 320x200 layout.

Saves and settings

Savegames are separated by a hash of the exact selected WAD filename:

ML/DOOM/SAVES/<iwad-hash>.D<slot>

Selecting a save slot with SET writes it directly; existing descriptions are retained and empty slots receive a map description. Input state is reset after a successful save so the controls do not remain stuck.

New saves include a Doom 550D format version and a fingerprint of the active WAD layout. Saves from a different or changed WAD and damaged saves are rejected with INCOMPATIBLE SAVEGAME instead of being partially applied. The loader validates maps, players, weapons, states, sprites, textures, sectors, thinkers and moving specials before gameplay resumes. Legacy v0.4 saves remain readable; incompatible Doom II weapons in Doom 1 are replaced with a valid shotgun or pistol and their weapon sprites are rebuilt.

Doom menu settings, music volume, and sound-effect volume are stored in:

ML/DOOM/CONFIG/

The selected WAD is stored in the Magic Lantern module configuration.

Debug logging

The Magic Lantern Games > Doom submenu contains two diagnostic controls:

• Debug logging is persistent and defaults to OFF. When enabled, the module writes engine, input and audio diagnostics to ML/LOGS/DOOM550D.LOG and ML/LOGS/DOOMRAW.LOG.
• Clear Doom logs removes only files matching ML/LOGS/DOOM*.LOG. It refuses to run while Doom is active and never removes WADs, savegames or configuration files.

Disabling logging does not automatically remove existing logs; use the clear action when they are no longer needed.

Audio

The module reads MUS lumps directly from the selected IWAD. A low-CPU integer synthesizer renders 24 band-limited voices at 24 kHz and linearly interpolates them into the 48 kHz Canon output, where they are mixed with Doom's original 8-bit sound effects. General MIDI program families select table-driven square, pulse, triangle or saw characters; percussion also uses noise. Attack, decay, sustain, release, channel volume and pitch bend are supported.

This gives an AdLib-like retro character while remaining light enough for fluid gameplay on the 550D. It is not cycle-accurate OPL2 emulation. Music and sound-effect levels are controlled independently from Doom's sound menu. When debug logging is enabled, audio timing and missed buffer deadlines are written to ML/LOGS/DOOM550D.LOG when Doom exits.

Porting to another Magic Lantern camera

The released doom.mo is not a portable binary. Never load the 550D module on another camera or firmware version. A port must be compiled against the exact Magic Lantern platform and firmware symbols for the target camera. Magic Lantern support alone does not guarantee that the display, buttons or Canon audio hardware use the same interface.

Most of the Doom engine, WAD handling, savegame code and music synthesizer can be reused unchanged. The camera-facing layer needs to be checked and usually adapted in these areas:

1. Magic Lantern build: build and boot the matching Magic Lantern core for the exact camera and firmware. First verify that a minimal module loads.
2. Display and palette: replace the 550D assumptions in doom550d.c about the 720x480 bitmap, BMPPITCH, 8-bit VRAM, LCD_Palette and palette writes through EngDrvOut. Confirm drawing, palette restoration and repeated game starts before enabling audio.
3. Buttons: determine the target camera's raw press and release event codes and replace the DOOM_BGMT_* values. Test held directions, simultaneous keys, menu navigation and release events. Do not assume the 550D button numbers or even the same set of physical buttons.
4. Audio: check build/doom.dep against the target platform's .sym file. The current backend expects StartASIFDMADAC, SetNextASIFDACBuffer, StopASIFDMADAC, SetSamplingRate, PowerAudioOutput, SetAudioVolumeOut, audio_configure and beep_playing. A camera with a different audio path needs a new backend, not just renamed symbols.
5. Storage and cleanup: verify Canon FIO reads and writes, directory creation, saves, configuration, error paths, display restoration, audio shutdown and module unload on the physical camera.
6. Regression testing: test several IWADs, new and overwritten saves, loading, every control, repeated starts, normal quit, forced module exit and at least one long play session after enabling debug logging and checking ML/LOGS/DOOM550D.LOG.

Keep the target camera's autoexec.bin, platform .sym file and newly built doom.mo together as one matching set. A useful contribution should identify the camera model, firmware version, Magic Lantern commit, toolchain version, module dependency result and every tested control. Physical access to the camera is required; emulator-only testing is not enough for input, palette, audio timing or cleanup.

Expected effort

These are estimates for one developer already comfortable with C, embedded debugging and Magic Lantern. They are engineering time, not guarantees; remote testing and unavailable camera logs can increase the calendar time greatly.

Target situation	Engineering work	Likely elapsed time
Closely related camera with matching bitmap and audio interfaces	3-7 working days	1-2 weeks
Different button map or display/palette behavior, but usable audio exports	1-3 weeks	2-6 weeks
Different or undocumented audio hardware, missing exports, or another DIGIC generation	4-8+ weeks	1-3+ months

A first build that merely loads may take only a day. A release-quality port takes longer because the difficult work is safe shutdown, held-button input, save/load reliability, audio deadline testing and repeated physical-camera regression tests. A second person who owns the target camera and can return logs quickly can shorten the elapsed time substantially.

Building doom.mo

Use the Magic Lantern source tree: https://github.com/reticulatedpines/magiclantern_simplified

Requirements:

• Git
• GNU Make
• Python 3
• arm-none-eabi-gcc
• ARM newlib headers and libraries

Place the module/ directory from this repository at modules/doom550d/ in the Magic Lantern tree, then run:

make -C modules/doom550d -j4

Output:

modules/doom550d/build/doom.mo

Every explicit module build also creates a source archive under modules/doom550d/source-backups/. Build products and source backups are ignored by Git.

Known limitations

• only Canon EOS 550D firmware 1.0.9 is supported;
• changing the WAD after Doom has run requires a camera restart;
• at most 32 IWADs are listed;
• incompatible non-Doom IWADs are not yet rejected reliably;
• PWAD/mod selection is not implemented;
• the synthesizer is AdLib-like, not cycle-accurate OPL2;
• multiplayer/network play is not supported;
• the secret cheat menu is available only during an active single-player level;
• when enabled, logs retain only the most recent run;
• this remains experimental software: keep SD-card backups.

Credits and license

• Doom engine source by id Software
• Doomgeneric
• Chocolate Doom
• Magic Lantern
• Freedoom contributors
• Bas Lichtjaar doom@lauris.nl and contributors to this port

This project is released under GPL-2.0. Third-party game assets are not included.