Fizzim FSM Editor for VS Code
A native VS Code editor for Fizzim .fzm finite
state machine diagrams. Draw state machines on a canvas and generate
synthesizable Verilog / SystemVerilog / VHDL — without leaving your editor.
Fizzim is a well-known FSM-design tool built as a Java/Swing desktop app. This
extension is a from-scratch reimplementation of its diagram editor as a VS Code
custom editor, reading and writing the exact same .fzm file format, so it's a
drop-in replacement for the desktop GUI.
Features
- Diagram editor: states, transitions, self-loops (loopbacks), free text,
and cross-page connectors on a zoomable canvas.
- Full property dialogs: per-state and per-transition attribute tables,
Mealy outputs, priority + Graycode encoding, custom colors.
- Global Attributes editor: inputs, outputs, flags, multi-bit signals,
reset signal/state, user attributes — all 5 tabs, matching the original GUI.
- Generate HDL: runs the bundled Fizzim code generator (
fizzim.pl) on the
current diagram and opens the resulting Verilog / SystemVerilog / VHDL.
Works out of the box — no separate install needed (Perl must be on your
system).
- Export PNG/JPEG, Page Setup, multi-page diagrams, dark-mode canvas
toggle, undo/redo, drag-select, keyboard shortcuts.
- A Fizzim-style menu bar (File / Edit / Global Attributes / View / Help) with
a modern VS Code look.
Getting started
- Install the extension.
- Open any
.fzm file, or run Fizzim: New Diagram from the Command
Palette.
- Right-click the canvas to add states, transitions, and text. Drag to move.
Delete removes the current selection.
Ctrl+S saves back to the .fzm file — the same format the original
Fizzim desktop app reads.- Use File → Generate HDL to produce Verilog/VHDL from the diagram.
Configuration
| Setting |
Default |
Description |
fizzim.perlPath |
perl |
Perl interpreter used to run the code generator. |
fizzim.scriptPath |
(empty) |
Override for fizzim.pl. Leave empty to use the version bundled with the extension. |
fizzim.language |
verilog |
Target HDL language: verilog, vhdl, or systemverilog. |
fizzim.darkMode |
false |
Draw the canvas on a dark background. |
fizzim.defaultStateColor |
#000000 |
Default color for new states. |
fizzim.defaultTransitionColor |
#000000 |
Default color for new transitions. |
fizzim.defaultLoopbackColor |
#000000 |
Default color for new loopback transitions. |
All of the above are also editable from the in-editor Preferences dialog.
Status
Feature parity with the original Fizzim GUI for the full edit → HDL workflow,
plus a few extras (zoom, dark mode, duplicate state). See
CHANGELOG.md for release notes.
Deliberately not ported (VS Code webview limitations or low value): File→Print,
Export→Clipboard, and a couple of cosmetic details in cross-page connector
rendering.
Development
npm install
npx tsc --noEmit # typecheck
npm run build # bundle extension + webview
npm test # unit tests (node --test)
npm run package # produce a .vsix
License
GPL-3.0-or-later, as a derivative of Fizzim
(© Zimmer Design Services). See LICENSE.
Fizzim itself is not affiliated with this project; this is an independent,
open-source reimplementation of its editor for VS Code.
