Velxio

Introduction

Velxio is a free open-source online circuit and microcontroller simulator with real-time SPICE analog simulation. Supports 19 boards across 5 CPU architectures including Arduino, ESP32, RP2040, ATtiny85. Run real firmware in the browser and observe circuit behavior. Supports custom chips (C/Rust/AssemblyScript). No account required, works offline.

Features

• Real-time SPICE simulation via ngspice-WASM, ~60 Hz solve rate
• Arduino Uno/Nano/Mega/Leonardo/Pro Mini ATmega328P/2560/32u4 AVR8 emulation
• Raspberry Pi Pico & Pico W (RP2040 ARM Cortex-M0+)
• ESP32/ESP32-S3/ESP32-CAM (Xtensa LX6/LX7 QEMU)
• ESP32-C3/CH32V003 (RISC-V QEMU)
• Raspberry Pi 3B (ARM Linux QEMU, runs Python)
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• Custom chips in C/Rust/AssemblyScript compiled to WebAssembly
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• 48+ interactive electronic components (LEDs, sensors, displays, etc.)
• Monaco Code Editor with arduino-cli compilation
• Serial monitor, library manager, multi-file workspace
• Open source (GNU AGPLv3), Docker self-hosting