About Velxio
A free, open-source embedded systems emulator — built by a single developer with a passion for hardware and open source.
The Story
Velxio started as a personal exploration into how microcontroller emulators work internally — CPU instructions, memory management, peripheral timing, and low-level architecture. What began as a learning project during a vacation quickly grew into something bigger.
The idea was simple: what if anyone could simulate Arduino, ESP32, and Raspberry Pi boards directly in the browser, without buying hardware, without installing toolchains, without cloud accounts?
Velxio v1 launched on Product Hunt and Hacker News, supporting Arduino Uno and Raspberry Pi Pico. The feedback from the maker and embedded community was incredible — and it pushed the project forward.
Velxio 2.0 shipped with ESP32 emulation via QEMU (using the lcgamboa fork), a Raspberry Pi 3 running real Linux, RISC-V support for ESP32-C3 and CH32V003, realistic sensor simulation (DHT22, HC-SR04, WS2812B NeoPixel), and 19 boards across 5 CPU architectures — all running real compiled code.
The v2 launch hit the front page of Hacker News for over 20 hours, reaching nearly 600 GitHub stars and thousands of visitors in less than 24 hours. It's now being used by students, professors, and makers around the world.
How It Works
AVR8 & RP2040
Cycle-accurate emulation runs entirely in your browser using avr8js and rp2040js. No backend needed for simulation.
ESP32 via QEMU
Xtensa ESP32 and ESP32-S3 run on backend QEMU (lcgamboa fork) with real flash images, GPIO, ADC, and timers.
RISC-V via QEMU
ESP32-C3 (DevKit, XIAO, SuperMini) and CH32V003 are emulated through the QEMU lcgamboa fork with libqemu-riscv32, the same backend pattern as Xtensa ESP32.
Raspberry Pi 3
Full ARM Cortex-A53 Linux via QEMU raspi3b — boots real Raspberry Pi OS and runs Python with RPi.GPIO.
Open Source Philosophy
Velxio is 100% open source under the AGPLv3 license. No cloud dependency, no student accounts, no data leaving your network. Universities and bootcamps can deploy it on their own servers with a single Docker command and give every student access to a complete embedded development environment — for free.
The project builds on top of amazing open-source work from the community:
- avr8js — AVR8 CPU emulation by Wokwi
- rp2040js — RP2040 emulation by Wokwi
- wokwi-elements — 48+ visual electronic components by Wokwi
- QEMU lcgamboa fork — ESP32 and Raspberry Pi QEMU emulation
- arduino-cli — Arduino compilation toolchain
Velxio was inspired by Wokwi, which is a fantastic tool. The goal of Velxio is to take a different path: fully open source, self-hostable, and supporting multiple heterogeneous boards in the same circuit.
The Creator
David Montero Crespo
Application Architect @ IBM · Montevideo, Uruguay
Application Architect with over 10 years of experience leading the development of large-scale enterprise ecosystems. Specialist in Generative AI (LLMs, RAG, LangChain), Cloud-Native architectures (OpenShift, Kubernetes), and certified Odoo ERP expert. Currently at IBM working on enterprise applications for the Uruguayan State Insurance Bank (BSE).
Studied Computer Science Engineering at Universidad de Oriente in Cuba (2012-2017), then moved to Uruguay where he built a career spanning roles at Quanam (Odoo implementations for government institutions), and IBM (enterprise architecture for BPS and BSE).
Programming and robotics enthusiast. Creator of other open-source projects including a 3D racing game running on an ESP32 (viral on Reddit with 40K+ views) and an iPod Classic clone for Raspberry Pi.
Tech Stack
Recent releases
Velxio 3.0
Retro CPUs, multi-board systems, full-circuit accuracy
Programmable Z80/8080/4004 retro CPUs with custom ROM, MicroSD and ePaper emulation, true multi-board UART/I2C/SPI interconnect, ESP32-CAM, full undo/redo, the complete ngspice WASM migration, an 88% smaller bundle, and 100+ new examples.
Read the launch notes →Velxio 2.5
Arduino meets SPICE in your browser
Real-time analog circuit simulation via ngspice-WASM, wired to Arduino, ESP32 and Raspberry Pi Pico. 100+ SPICE-accurate components, live ammeters and voltmeters, 40 new analog/hybrid examples — co-simulated with your firmware.
Read the launch notes →Velxio 2.0
Multi-board canvas, ESP32, Raspberry Pi 3
Full QEMU-driven ESP32 emulation with WiFi/BLE, Raspberry Pi 3B Linux, MicroPython support across Pico/ESP32, custom WASM chips, and a redesigned canvas with multi-board co-simulation.
Read the launch notes →"I studied Computer Science in Cuba from 2012 to 2017, and when I moved to Uruguay, the most common question was: 'How did you graduate as an engineer without internet, without a computer, without YouTube?'
I only had 4 words for the answer: Perseverance! Perseverance! Perseverance! Perseverance!
There is no better motivation than not having a plan B."
— David Montero Crespo
Community & Press
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No signup required. Runs 100% in your browser. Free and open source.