Velxio 2.0 – Emulate Arduino, ESP32, and Raspberry Pi 3 in the Browser (github.com)

Hey HN, I posted Velxio here a while back and got great feedback. Since then I've shipped a major update

What's new in v2:

- 19 boards across 5 CPU architectures (AVR8, Xtensa, RISC-V, ARM Cortex-M0+, ARM Cortex-A53) - ESP32 emulation via QEMU (lcgamboa fork) — real flash images, ROM function emulation, GPIO/ADC/timers - ESP32-C3 and CH32V003 run on a custom RISC-V core written in TypeScript, entirely in the browser - Raspberry Pi 3B via QEMU raspi3b — boots real Pi OS, runs Python - Realistic sensor simulation: DHT22 (40-bit protocol timing), HC-SR04 (trigger/echo), WS2812B NeoPixel (GRB decoding) - 48+ electronic components from wokwi-elements

Architecture:

- AVR, RP2040, and RISC-V emulation runs client-side (avr8js, rp2040js, custom TS core) - ESP32 Xtensa and Pi 3 run on backend QEMU - Compilation via real arduino-cli - React + Vite frontend, FastAPI backend - Self-hostable via Docker, no account needed

Source: https://github.com/davidmonterocrespo24/velxio (AGPLv3)

Happy to discuss the emulation architecture — particularly the trade-offs between in-browser vs. backend QEMU emulation

Velxio 2.0 is live.

A free, open-source emulator for 19 embedded boards: Arduino, ESP32, Raspberry Pi, RISC-V , running real compiled code in your browser.

The best part: it's fully local.

No cloud dependency. No student accounts. No data leaving your network. Self-hostable with a single Docker container.

Universities and bootcamps can deploy it on their own servers and give every student access to a complete embedded development environment, for free.

I've been working on this for over a year, and just shipped v2.0 with ESP32 emulation (via QEMU), a custom RISC-V core, and Raspberry Pi 3 support that runs real Python

First of all: Awesome work! Playing with it now.

One suggestion: The main splash screen image is nearly 8MB big. It takes a noticeable time to download on my connection. I'm not sure what bandwidth costs these days, but seems like that could be something to optimize.

I often write a bunch of Esphome ‘code’ , which I then use with various esp32 based devices (mostly from M5stack) via esphome/HomeAssistant.

Can this project help me in any way during dev stage before uploading the code to device just to see it doesn’t work ? Eg could I use this to somehow compile&run those esphome yamls via this emulator?

This is a great idea. It’s always been inconvenient requiring access to the physical board just to be able to test these sort of projects.

Nice work! One minor point for me: it wasn’t immediately clear that you need to press Compile before Play gets enabled (e.g. Arduino IDE let's you upload right away and compiles if needed)

Can someone who has used both wokwi and this do a compare/contrast? The footer suggests that it's built on top of wokwi-elements

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The container instructions has `-d` in it, but note that after booting the container it downloads another, I don't know, 300+mb more (its still downloading as I write), so if you can't connect that's why.

Might be better to not include `-d` in the instructions?

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Awesome. Is there any chance of getting MicroPython or CircuitPython support?

Quick update: traffic is still coming in waves, had to scale up compilation workers to keep up with demand

Things are more stable now, but still tuning performance under load

If anyone finds it useful, the source is here: https://github.com/davidmonterocrespo24/velxio

Always happy to get feedback or contributions.

This is fantastic. I am doing my first-ever consumer electronics product and this would save a lot of soldering time

I like this Idea but I don't want to use this. I know what kind of prompt U using to create this one: "Create something like Wokwi and make it local"

Pretty cool project! if you're checking it out, try one of the built-in examples and hit "Compile + Play". It runs immediately, no setup required

Great project! Now all there is left to do is a VS Code plugin. Also make it play nice with platform io.

Abang

Nice Project. One of the benefits of such small boards is the ability to provide a "Hands on" experience. Use your hands to wire, press buttons and turn knobs. Emulating all this is a big thing but it takes away the learning in my eyes. It's like flying drones. It looks cool but gets boring after 10 minutes.

That looks awesome, thank you for your hard work! I would love tinker with it, but I'm not sure how to abstract things connected to those supported u_controller boards? Example, 7x16 Pico unicorn hat is driven by RP2040 PIO.

Good job

Isn't the problem with these emulations that they are not realtime and therefore will never give true feedback? As in the simulation will unlikely to translate to real world behaviour.

Really impressive - browser-based hardware emulation is a brutal WebAssembly performance problem. Curious what you're doing for the rendering layer: are the circuit visualizations on canvas/WebGL, or DOM-based? I've been hitting similar render-loop problems with a deck.gl mapping project (realtime vessel positions, thousands of points updating simultaneously) and the pattern I found that helped most was batching state updates on a fixed 2s interval before diffing the render layer - prevents the WebGL context from recomposing faster than the data actually changes meaningfully. Does Velxio have a similar throttle, or does it redraw on every emulation tick?

From what I can see, I cannot give it an ESP32-C6 firmware binary to execute, I have to compile my source code (C only) and the source has to use Arduino APIs. Under the hood it's still QEMU.

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