<metaname="description"content="Velxio is a free, open-source circuit and microcontroller simulator running in your browser. Real-time SPICE analog simulation (ngspice-WASM) wired to 19 boards: Arduino Uno/Nano/Mega/ATtiny85 (AVR8), ESP32 / ESP32-S3 (Xtensa QEMU), ESP32-C3 / CH32V003 (RISC-V), Raspberry Pi Pico (RP2040), Raspberry Pi 3 (Linux ARM). 100+ components, custom chips in C/Rust, oscilloscope, voltmeter, ammeter — no cloud, no account."/>
<metaproperty="og:description"content="Hybrid digital + analog circuit simulator in your browser. SPICE-accurate analog (ngspice-WASM) wired to 19 boards: Arduino Uno/Nano/Mega/ATtiny85, ESP32, RP2040, RISC-V, Raspberry Pi 3 Linux. Build custom chips in C/Rust. 100+ components, oscilloscope, voltmeter — no cloud."/>
<metaname="twitter:description"content="Hybrid digital + analog circuit simulator in your browser. SPICE-accurate analog (ngspice-WASM) co-simulated with Arduino, ESP32, RP2040, ATtiny85. Build custom chips in C/Rust. 100+ components — free, no cloud."/>
"description": "Free open-source circuit and microcontroller simulator. SPICE-accurate analog co-simulation wired to Arduino, ESP32, RP2040, ATtiny85, and Raspberry Pi 3 — all running in the browser.",
"description": "Free, open-source online circuit and microcontroller simulator running entirely in the browser. Real-time SPICE analog co-simulation via ngspice-WASM (resistors, capacitors, op-amps, transistors, diodes, voltage regulators) wired to 19 boards across 5 CPU architectures: ATmega328p/2560/ATtiny85 (AVR8 via avr8js), RP2040 ARM Cortex-M0+ (rp2040js), ESP32-C3/CH32V003 RISC-V RV32IMC (browser), ESP32/ESP32-S3 Xtensa LX6/LX7 (QEMU), and Raspberry Pi 3B ARM Cortex-A53 (QEMU Linux). Build custom chips in C/Rust/AssemblyScript via the Wokwi Custom Chips API. Includes live oscilloscope, voltmeter, ammeter, signal generator, 100+ interactive electronic components, Monaco Editor, Serial Monitor, arduino-cli compilation, and Library Manager.",
"description": "Velxio is a free, open-source online circuit simulator with hybrid digital + analog SPICE co-simulation, 19 supported boards, custom chip authoring, and 100+ components — all in your browser.",
<h2>Free online circuit + microcontroller simulator — SPICE-accurate analog wired to Arduino, ESP32, RP2040, ATtiny85 & more</h2>
<p>Velxio is a free, open-source online circuit simulator with hybrid digital + analog co-simulation. Real-time SPICE analysis (ngspice-WASM) wired to 19 supported boards across 5 CPU architectures. Build custom chips in C, Rust, or AssemblyScript. 100+ interactive components, live oscilloscope, voltmeter, ammeter, Monaco Editor, Serial Monitor, arduino-cli compiler, and Library Manager — no cloud, no latency, no account required.</p>
<h3>What's new in Velxio 2.5</h3>
<ul>
<li><strong>Real-time SPICE analog simulation</strong> in your browser via ngspice-WASM (eecircuit-engine) — Modified Nodal Analysis at ~60 Hz, not a linear approximation</li>
<li><strong>Hybrid digital + analog co-simulation</strong> — GPIO pins drive SPICE nets as voltage sources; <code>analogRead()</code> reads solved node voltages back into firmware</li>
<li><strong>Live instruments</strong>: oscilloscope (multi-channel), voltmeter, ammeter, signal generator (sine/square/DC)</li>
<li><strong>40+ new analog & hybrid examples</strong>: voltage divider, RC filter, full-wave rectifier, Schmitt trigger, op-amp amplifier, Wheatstone bridge, H-bridge motor driver</li>
<li><strong>Custom Chips</strong> — author your own integrated circuits in C, Rust, or AssemblyScript using the Wokwi Custom Chips API; reuse them across projects</li>
<dd>The simulation engine — including the SPICE analog solver and all browser-side CPU emulators (AVR8, RP2040, RISC-V) — runs entirely in the browser. Compilation requires the local arduino-cli backend. Self-hosted deployments work fully offline once running.</dd>
<dt>Can Velxio simulate analog circuits like SPICE?</dt>
<dd>Yes. Velxio 2.5 includes real-time SPICE analog simulation via ngspice compiled to WebAssembly. It runs full Modified Nodal Analysis on every tick — non-linear devices (diodes, BJTs, MOSFETs, op-amps with saturation) behave like real silicon, not idealised models.</dd>
<dt>Can I co-simulate Arduino code with an analog circuit?</dt>
<dd>Yes. GPIO pins drive SPICE nets as voltage sources, and ADC pins read solved analog node voltages back into firmware. <code>analogRead()</code> returns the actual SPICE-solved value at that net — so you can build PWM-driven RC filters, transistor switches, op-amp signal chains, and motor drivers end-to-end on the same canvas.</dd>
<dt>Can I create my own custom chips?</dt>
<dd>Yes. Velxio implements the Wokwi Custom Chips API. Write your chip logic in C, Rust, or AssemblyScript — Velxio compiles it to WebAssembly and exposes pin I/O, attribute reads, timers, and I²C/SPI hooks. Save chips to your account and reuse them across projects.</dd>
<dd>Yes. Velxio is a free, self-hosted alternative to Wokwi. It uses the same avr8js and wokwi-elements open-source libraries but runs on your own machine, and adds full SPICE analog co-simulation that Wokwi does not provide.</dd>
<dt>Is Velxio a Falstad / Tinkercad / CircuitLab alternative?</dt>
<dd>For analog circuits, yes. Velxio runs the open-source ngspice solver — the same engine professional EDA tools use. Unlike Falstad and Tinkercad, Velxio also runs the firmware on the microcontroller driving the circuit.</dd>
<p>Velxio is a free online circuit simulator with real-time SPICE analog simulation in your browser. Drop resistors, capacitors, op-amps, transistors, diodes, and voltage regulators on the canvas — every component is modelled with real ngspice device cards, not behavioural stand-ins. <ahref="/circuit-simulator">Open Circuit Simulator →</a></p>
<ul>
<li>ngspice-WASM engine — full Modified Nodal Analysis at ~60 Hz solve rate</li>
<li>Non-linear devices behave like real silicon: BJT cutoff/saturation, op-amp rails, diode forward drop</li>
<li>Live oscilloscope, voltmeter, ammeter, signal generator</li>
<li>Always-on — no toggle, every circuit is SPICE-solved</li>
</ul>
</section>
<section>
<h2>SPICE Simulator Online — ngspice in Your Browser</h2>
<p>Velxio runs ngspice (the open-source SPICE simulator powering professional EDA tools) compiled to WebAssembly via eecircuit-engine. Full transient analysis, real device models, in your browser tab. No install, no account, works offline after the first load. <ahref="/spice-simulator">Open SPICE Simulator →</a></p>
<ul>
<li>Real ngspice — same engine, browser-native via WASM</li>
<h2>Custom Chip Simulator — Define Your Own ICs in C / Rust</h2>
<p>Velxio implements the Wokwi Custom Chips API: write your chip logic in C, Rust, or AssemblyScript, compile to WebAssembly, and the simulator drives its pins like any other component. Build a sensor model, a digital protocol bridge, or a behavioural IC stand-in — and reuse it across projects. <ahref="/custom-chip-simulator">Open Custom Chip Simulator →</a></p>
<ul>
<li>Wokwi-compatible Custom Chips API with WASI shim</li>
<li>Save chips to your account and reuse across projects</li>
<li>Library of starter examples (sensors, decoders, bridges)</li>
</ul>
</section>
<section>
<h2>ATtiny85 Simulator — Real AVR Emulation in Your Browser</h2>
<p>Velxio simulates the ATtiny85 with cycle-accurate AVR8 emulation. Full DIP-8 pinout, 8 KB flash, 6 GPIOs, USI peripheral, 10-bit ADC, Timer0/Timer1 with PWM, and watchdog. Wire it to LEDs, sensors, or analog circuits and run real ATtiny code without a programmer. <ahref="/attiny85-simulator">Open ATtiny85 Simulator →</a></p>
<ul>
<li>Cycle-accurate ATtiny85 emulation via avr8js</li>
<li>All 6 I/O pins (PB0–PB5) with proper port behaviour</li>
<p>Velxio is a free online Arduino simulator with real AVR8 emulation at 16 MHz. Simulate Arduino code with 48+ interactive electronic components directly in your browser — no install, no account required. <ahref="/arduino-simulator">Open Arduino Simulator →</a></p>
<ul>
<li>Arduino Uno (ATmega328P) simulation at 16 MHz</li>
<li>Serial Monitor with auto baud-rate detection</li>
<li>Multi-file sketch support (.ino, .h, .cpp)</li>
<li>Free and open-source (GNU AGPLv3)</li>
</ul>
</section>
<section>
<h2>Arduino Emulator — Real AVR8 & RP2040 Emulation</h2>
<p>Velxio is a cycle-accurate Arduino emulator built on avr8js and rp2040js. Every AVR opcode is faithfully emulated at 16 MHz — the same silicon behavior as real hardware. <ahref="/arduino-emulator">Open Arduino Emulator →</a></p>
<ul>
<li>All 135 AVR8 instructions emulated</li>
<li>Hardware timers (Timer0/1/2) with PWM, CTC, and overflow interrupts</li>
<li>10-bit ADC, full USART0 (TX/RX), SPI, I2C</li>
<li>RP2040 dual-core ARM Cortex-M0+ via rp2040js</li>
<li>RISC-V RV32IMC (ESP32-C3) emulation in browser</li>
</ul>
</section>
<section>
<h2>ATmega328P Simulator</h2>
<p>Simulate ATmega328P firmware exactly as it runs on Arduino Uno and Nano. Full AVR8 emulation: PORTB, PORTC, PORTD, Timer0/1/2, ADC, USART0, and all interrupt vectors. <ahref="/atmega328p-simulator">Open ATmega328P Simulator →</a></p>
<li>Timer0 (8-bit), Timer1 (16-bit), Timer2 (8-bit) — all PWM modes</li>
<li>10-bit ADC, 6 analog channels (A0–A5)</li>
<li>USART0 with configurable baud rate</li>
</ul>
</section>
<section>
<h2>Arduino Mega 2560 Simulator</h2>
<p>Simulate Arduino Mega 2560 (ATmega2560) code for free. 256 KB flash, 54 digital pins, 16 analog inputs, 4 hardware serial ports (Serial, Serial1, Serial2, Serial3), and 6 hardware timers. <ahref="/arduino-mega-simulator">Open Mega 2560 Simulator →</a></p>
