What is velxio?

Velxio is an open source, fully local emulator for Arduino, ESP32, and Raspberry Pi boards that runs entirely in the browser. A user writes Arduino style C++ or Python code, compiles it, and simulates it against real CPU emulation and more than forty eight interactive electronic components, without needing any physical hardware or a cloud service. The project supports nineteen boards across five different CPU architectures: AVR8 chips like the ATmega and ATtiny used in classic Arduino boards, the ARM Cortex M0 plus core in the Raspberry Pi Pico, RISC V cores in the ESP32 C3 and CH32V003, the Xtensa architecture in the ESP32 and ESP32 S3 run through QEMU, and the ARM Cortex A53 core in a full Raspberry Pi 3 Linux emulation, also through QEMU. Multiple boards can be placed on the same canvas and wired together over simulated serial connections, even when they use different underlying architectures. The code editor is built on Monaco, the same editor that powers Visual Studio Code, and supports a multi file workspace where a user can create, rename, and switch between C++, header, and Python files. Arduino sketches compile through the arduino-cli backend into hex or binary files. A library manager loads the full Arduino library index so users can browse and install libraries without needing to know the exact package name in advance. Velxio is available as a hosted service at velxio.dev with no installation required, or it can be self hosted with a single Docker command. Named Docker volumes preserve build caches between container restarts, since without them each restart can push ESP32 compile times up to five to seven minutes instead of five to thirty seconds. The project is licensed under AGPLv3, with a separate commercial license available for cases where the copyleft terms of AGPL do not fit.