Velxio

What it does

It allows you to write Arduino sketches, compile them using arduino-cli, and simulate circuits with a real AVR8 CPU emulator and interactive electronic components. The platform supports multiple boards including Arduino Uno, Nano, Mega, and Raspberry Pi Pico, with peripherals such as GPIO, SPI, I2C, UART, and ADC mapped to visual components. The goal of the project is to create an open-source environment where developers and makers can experiment with Arduino circuits

Velxio is a free, open-source online circuit simulator. Real-time SPICE analog simulation (ngspice-WASM) wired to 19 boards: Arduino Uno/Mega/ATtiny85 (AVR8), ESP32 (Xtensa QEMU), ESP32-C3/CH32V003 (RISC-V via QEMU libqemu-riscv32), Raspberry Pi Pico (RP2040), Raspberry Pi 3 (Linux). Build custom chips in C/Rust. 100+ components, oscilloscope, voltmeter, ammeter — no cloud.

Hardware is all about iteration. Velxio lets you wire a circuit, program the board and run it in seconds, real firmware on a real solver, right in the browser. Nothing on this page is a scripted animation: the firmware is compiled and executed, and the circuit around it is solved. arduino-cli compiles it, an AVR8 core executes it instruction by instruction, and the LCD shows what the ATmega328P actually put on the bus. Uno, Nano, Mega and ATtiny85, no board on your desk. arduino-cli or ESP-IDF compiles the sketch, then AVR8, RP2040, RISC-V, Xtensa or ARM executes it instruction by instruction. What the OLED draws and what the serial monitor prints is what the chip actually did. ngspice…from velxio.dev

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