Velxio 3.0
Retro CPUs, multi-board systems, full-circuit accuracy
Velxio 3.0 is the biggest release yet. Program classic Z80, 8080 and 4004 processors, emulate MicroSD cards and ePaper displays, wire entire multi-board systems together, and undo any mistake on the canvas. Over 100 new examples — all free, open-source, and running in your browser.
The biggest Velxio release yet
Velxio 2.5 brought real analog circuits. Velxio 3.0 expands in every direction at once — new processors, storage and displays, true multi-board systems, sharper simulation, and the editor polish you have been asking for.
Classic CPUs, fully programmable
Drop a Z80, 8080, 4004, 4040 or 8086 on the canvas, load your own ROM, and write assembly right in the editor — no host board required.
Whole systems, not single boards
Wire UART, I2C, SPI and plain GPIO across every supported board. An ESP32 talking to a Pico talking to an Arduino, all solved on the same clock.
Undo, minimap, live editing
Full undo/redo for every canvas action, a draggable minimap to navigate big builds, and drag-to-move parts while the simulation is running.
Everything new in 3.0
A complete tour of the release — new processors, storage and displays, multi-board interconnect, simulation accuracy, performance, and over a hundred fresh examples.
Retro CPU Chips
- Z80, Intel 8080, 4004, 4040 and 8086 processors
- Programmable ROM — load your own machine code
- Board-less operation: run a bare CPU with no host board
- In-editor assembly support for retro targets
- Step a classic instruction set right on the canvas
- Pair retro CPUs with modern peripherals
Storage & ePaper Displays
- MicroSD card emulation over SPI (AVR, RP2040, ESP32)
- FAT16 image with an upload panel — read and write real files
- ePaper SSD168x panels: black/white and tri-colour
- UC8159c ACeP 7-colour ePaper
- UC8179 mono ePaper with correct rotation and BUSY timing
- Byte-aware panel orientation across every board
Multi-Board Interconnect
- Wire-aware UART, I2C, SPI and digital links across boards
- An ESP32, a Pico and an Arduino on one canvas, talking
- SignalRouter for ESP32 GPIO Matrix routing
- ESP32-CAM emulation with a real webcam frame bridge via QEMU
- Board removal reconciles the running simulation cleanly
- Every supported board can interconnect
Library Manager
- Per-board library manifests scoped to each compile
- Content-addressed cache — deduped, fast and shared
- Version management, uninstall, and autocomplete
- src/-layout libraries (ArduinoJson, etc.) compile correctly
- Single unified tab with state-aware row actions
- Add to project / In project / Remove in one place
Simulation Accuracy
- Full ngspice WASM migration — one solver path, browser and Node
- PinResolver: SPICE-resolved digital inputs for mixed-mode
- Oscilloscope trigger modes — Auto, Normal, Single
- Edge selection and trigger-position control
- RP2040 real-time: IdleSpinDetector elides busy-wait loops
- AVR and ESP32 UART waveforms synthesized at the bit level
Editor & Canvas
- Full undo/redo: components, wires, moves, rotations, properties
- Drag-to-move parts while the simulation runs
- Wires follow component rotation automatically
- Component deletion cascades to connected wires
- Board options modal and per-target compile console
Performance
- Main bundle cut 88% — from ~23 MB to ~2.68 MB
- manualChunks split wokwi-elements, terminal and MCU emulators
- ESP-IDF warm compiles drop from 5-7 min to 5-30 s
- ccache with an 8 GB cap and persistent build directories
- Compilation dedup stops duplicate ninja jobs racing
- Faster SPI/I2C waveform rendering via worker batching
Pro & Desktop
- GitHub Sync, Share/Embed modal, BOM CSV and schematic PNG export
- Desktop app: welcome page, license gating, native menubar
- In-app update toast and a splash screen during boot
- i18n across 9 locales (en, es, pt-br, it, fr, zh-cn, de, ja, ru)
- Extension hooks for private overlays (auth, session, agent chat)
- .vlx project export/import for stateless self-hosters
Examples & Testing
- 100+ new gallery examples added
- Pico Doom, ESP32-CAM preview, ePaper dashboards, retro-CPU demos
- A 100 Days of IoT series and dozens of analog circuits
- Netlist snapshot tests for every gallery example
- Visual LED test harness driven over Chrome DevTools Protocol
- Backend end-to-end tests re-enabled in CI
100+ new gallery examples
Pico Doom, ESP32-CAM previews, ePaper dashboards, retro-CPU demos, a 100 Days of IoT series, and dozens of analog circuits — every one a single click away.
The outcome
Velxio 3.0 turns a board simulator into a full embedded-systems workbench: processors, peripherals, storage, displays and circuits, together in one browser tab.
Build complete systems
Multi-board projects with real UART/I2C/SPI links, MicroSD storage, and ePaper or webcam output — prototyped end to end before you touch hardware.
Learn from retro to modern
Trace a 4-bit Intel 4004 instruction by instruction, then jump to a 32-bit RISC-V or a quad-core ARM Linux board — the same canvas, the same tools.
Still 100% open source
AGPL-3.0 on GitHub. No account, no cloud, no install. Fork it, self-host it, extend it.
Built on open-source
Velxio 3.0 stands on decades of open-source emulation and EDA work. Huge thanks to the maintainers of every project below.
ngspice
The open-source SPICE circuit simulator — now the single analog solver across browser and tests
QEMU
Powers ESP32 (Xtensa), RISC-V, ARM and the new ESP32-CAM webcam bridge
avr8js
AVR8 CPU emulator in JavaScript — Arduino Uno, Nano, Mega, ATtiny85
rp2040js
RP2040 emulator — Raspberry Pi Pico and Pico W, now running in real time
wokwi-elements
Web Components for electronic parts — LEDs, buttons, sensors, displays
Velxio
This project — free, open-source embedded systems & circuit simulator
Try Velxio 3.0 now
Open the editor and start building — processors, peripherals, circuits and multi-board systems, with zero setup.
Launch Simulator