Zoom MultiStomp ZDL

Custom .ZDL effects for Zoom MultiStomp pedals, plus the reverse-engineered toolchain used to build them.

Custom effect pack

This fork is a consolidated custom library of 17 effects — all grouped under the Delay category, each with a custom on-device cover. Originals: granular shimmer, drum glitch, tape degradation, a Dune-style drone, a Data Corrupter-style synth, ring mod, high-gain amp+cab, a feedback howl, and tape saturation. Plus rebuilt/renamed Airwindows-derived ports: reverbs, stereo chorus, and tape. See CUSTOM_EFFECTS.md for details, knob layouts, and sound demos.

Not all hardware-verified yet, and the pedal can't hold/run all 17 at once (storage + DSP limits) — install a curated subset, back up first, flash one at a time. See CUSTOM_EFFECTS.md.

Download Effects

The ready-to-load effects are in dist/. Point Zoom Effect Manager at that folder, or download individual .ZDL files from it. You do not need the build toolchain unless you want to modify or rebuild effects.

Install With Zoom Effect Manager

Use Zoom Effect Manager 2.3.3 or newer.

1. Open Zoom Effect Manager, connect your pedal, then open Settings.
2. Choose Read Effects from folder and select this repo's dist/ folder.

3. In the effect browser, enable Effects from devices and From Folder.
4. Add the desired effects to the device and write them with Zoom Effect Manager.

Back up your current effect list before writing. This project is still reverse engineering firmware behavior, and experimental builds can crash or freeze a pedal until power-cycled.

More detailed install notes live in docs/INSTALLING-ZDLS.md.

Compatibility

Hardware testing is still narrow. Treat every model outside the confirmed row as unverified until someone reports a clean load and audio test.

Device family	Status
Zoom MS-70CDR firmware 2.10	Primary hardware target; current release effects have been developed against this pedal.
Other ZDL-based Zoom MultiStomp pedals	Unconfirmed. They may load compatible ZDLs, but need hardware reports.
Newer Zoom ZD2-based pedals	Not supported by these ZDL builds.

Build Your Own Effects

Start from src/airwindows/gain/ if you want the smallest working custom effect. Copy that directory, give the effect a new name and unused fxid in manifest.json, then update the C audio function and build.py to use the new names. Add the new build script to build_all.py once it builds on its own.

Keep the first hardware test boring: audio_nop: true or tiny pass-through DSP, no large static state, no heap, and no new runtime helper calls. The safe path is documented in docs/SAFE-DSP-RULES.md and the effect directory conventions are summarized in src/airwindows/README.md.

Known Issues

• Only the Zoom MS-70CDR firmware 2.10 has been tested seriously so far.
• Experimental builds can freeze or crash the pedal until it is power-cycled.
• ToTape9.ZDL now loads and runs on the test MS-70CDR after removing runtime __c6xabi_divf from the full DSP path. It is still under validation for parameter initialization, preset behavior, and source-equivalent exactness. The latest build treats zeroed parameter slots as unmaterialized defaults to address the reload mute report; this still needs hardware confirmation.
• VerbTiny.ZDL is a new Airwindows reverb port candidate. It builds cleanly with ctx[3] state and no object relocations, but it has not been hardware-tested yet.
• Galactic.ZDL is a larger Airwindows reverb candidate. It builds cleanly with about 528 KB of ctx[3] state and no object relocations, but it has not been hardware-tested yet.
• TEcho4.ZDL is a custom Airwindows-inspired tape echo, not a 1:1 Airwindows port. It builds as a Delay-category effect with ctx[3] delay memory, a compact FIR derived from a UAD Galaxy Tape Echo IR, TapeHack-style saturation, adjustable wear filtering, measured wow/flutter, a compact mono spring fallback, and a BPM+division tempo workflow. Desktop listening has selected a closer Galaxy spring reference model: a 744 ms measured body plus an eight-line FDN tail. Porting that longer spring model into the bounded pedal runtime remains pending. Hardware result is pending; true host tap tempo for custom ZDLs is still unproven.
• ZDL filenames should have unique basenames of 8 characters or less. Zoom tooling/device code can truncate longer basenames, so collisions like TapeEcho4.ZDL -> TapeEcho.ZDL can create duplicate effect identities and freeze the pedal when loading. This repo now ships that effect as TEcho4.ZDL.
• OTT.ZDL is a custom Dynamics-category OTT-style multiband compressor, not an Ableton port. It exposes DryWet, Time, Output, and SplitFrq, and builds cleanly with small ctx[3] state, no .fardata, no .text, and no object relocations. Hardware result is pending.
• On MS-70CDR, Drive-category custom effects may not appear in the on-device FX browser unless at least one stock Drive effect is also installed. ToTape9 is intentionally categorized as Drive, so install a stock Drive effect too if it flashes but does not show up when scrolling the pedal.
• Parameter scaling is part of the porting work. A port should not be called source-equivalent until its raw knob ranges have been confirmed on hardware.
• These are .ZDL builds, not .ZD2 builds.

Documentation

Start here if you want more than the download folder:

Doc	What it covers
docs/INSTALLING-ZDLS.md	Step-by-step Zoom Effect Manager folder install.
docs/ZDL-REVERSE-ENGINEERING-STATUS.md	Current map of the ZDL wrapper, runtime ABI, and known state fields.
docs/STATE-ABI-PROGRESS.md	Compact current map of hardware-proven state/edit-handler findings.
docs/AIRWINDOWS-1TO1-PORT-ROADMAP.md	Roadmap for making honest source-equivalent Airwindows ports.
docs/AIRWINDOWS-EXACT-PORTS.md	Rules for what can and cannot be called a 1:1 Airwindows port.
docs/SAFE-DSP-RULES.md	Pedal-safe DSP/linking constraints learned from hardware failures.
docs/3-PARAM-LINKER-BUG.md	Investigation of the old edit-mode parameter-count bug.
docs/TI-PDF-NOTES.md	Notes distilled from the TI C6000 manuals in this folder.
docs/CONTRIBUTING.md	Hardware-test asks and contribution notes.
docs/sprab89b.pdf	TI C6000 application note reference.
docs/sprui03f.pdf	TI C6000 compiler/toolchain reference.
docs/sprui04g.pdf	TI C6000 assembly/linker tools reference.
build/ABI.md	Low-level linker/runtime ABI reference for developers.

Build From Source

Desktop listening previews are available before flashing hardware. See tools/audio_preview/README.md for the manifest-driven WAV renderer and current adapter coverage.

Building requires Python 3.10+ and TI C6000 Code Generation Tools. Installing prebuilt effects from dist/ does not.

The build scripts currently expect the TI compiler here:

/Applications/ti/ccs2050/ccs/tools/compiler/ti-cgt-c6000_8.5.0.LTS

On Linux, Windows, or another Code Composer Studio install, update TI_ROOT in the relevant src/airwindows/*/build.py or src/custom/*/build.py.

Build release effects:

python3 -B build_all.py

Build one effect:

python3 -B build_all.py stereochorus
python3 -B build_all.py tapeecho4
python3 -B build_all.py ott
python3 -B build_all.py totape9
python3 -B build_all.py verbtiny

Build diagnostic/probe effects too:

python3 -B build_all.py --all

The default build intentionally keeps dist/ clean and release-focused. Diagnostic ZDLs are useful for development, but are moved to build/probes/ and should not be mixed into the download folder.

Technical Notes

This repo builds loadable Zoom .ZDL effects without Zoom's unreleased SDK. The core pieces are:

Path	Purpose
build/linker.py	Static linker: TI C6000 .obj -> complete Zoom .ZDL.
src/airwindows/	Effect sources, manifests, images, and per-effect build scripts.
src/custom/	Original non-Airwindows effects built with the same linker/safety rules.
src/hardware_probes/	Diagnostic ZDLs used to map the pedal runtime ABI.
dist/	Release .ZDL files for users; never probes.
stock_zdls/	Tracked 830-file stock ZDL corpus used for comparison.

The important recent finding is that custom effects can use the host-managed large state descriptor at ctx[3]. That made the stateful StereoChorus port possible, and the no-divide ToTape9 full-kernel build now also loads and runs on the test MS-70CDR. VerbTiny and Galactic are reverb candidates using the same large-state strategy. TEcho4 / TapeEcho4 uses that same safe state pattern for a custom tape-delay design, and OTT uses a small ctx[3] state block for multiband envelope/gain history. The next ToTape9 work is parameter/default lifecycle validation and source-equivalence testing.

Known runtime map for custom ZDLs:

Field	Meaning
ctx[1]	parameter float table
ctx[4]	dry/guitar input buffer
ctx[5]	current effect buffer, 8 left samples then 8 right samples
ctx[6]	output accumulator for effects that add instead of processing in place
ctx[11] / ctx[12]	magic shuttle; preserve every audio call
ctx[2] + 0x10 / ctx[2] + 0x18	small persistent per-instance state blocks
ctx[3][0..2]	large per-instance descriptor: base, end, byte span

Parameter scaling is not universal across every handler path. StereoChorus showed that the current release handler path behaves like normalized 0..1 knob floats, while older helper assumptions saturated around UI value 14. Effects that claim source-compatible control laws should document how their raw parameter scaling was confirmed.

Repository Layout

ZoomMultistompZDL/
├── README.md
├── build/                 linker, ELF/ZDL helpers, stock-derived handler blobs
├── docs/                  install notes, ABI status, and porting guidance
├── dist/                  release ZDLs to load in Zoom Effect Manager
├── src/hardware_probes/       diagnostic ZDLs for runtime ABI experiments
├── src/airwindows/        effect sources, manifests, and build scripts
├── src/custom/            original non-Airwindows effects
├── stock_zdls/            tracked 830-file stock ZDL corpus used for comparison
└── build_all.py           release/probe build entrypoint

Several research references are useful locally but are intentionally ignored by git, so they are not part of this repo checkout:

airwindows-ref/          optional full Airwindows source tree
zoom-fx-modding-ref/     optional community ZDL notes and disassembly walkthroughs
ZoomPedalFun-main/       optional independent Zoom firmware RE work

If you clone those beside the repo, keep treating them as read-only references.

Contributing

Hardware reports are gold. When testing a ZDL, please include:

Item	Example
Pedal model and firmware	MS-70CDR firmware 2.10
ZDL filename and commit	StChorus.ZDL @ cee0d8a
Load result	boots, freezes on startup, freezes on unbypass
Audio result	bypass, dry passthrough, chorus works, high-pitched tone
Parameter behavior	Speed works 0..100, Depth saturates, page 2 knob missing

Open an issue or PR with findings. Keep experimental claims precise: "boots on my MS-70CDR" is more useful than "works everywhere."

License

Repository code is MIT unless a file says otherwise. Airwindows plugin DSP is MIT by Chris Johnson/Airwindows. Zoom firmware, stock effects, and third-party reference material are owned by their respective authors and are used only for interoperability and reverse-engineering research.