Arduino, running the sketch you wrote
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.

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.
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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 compiled to WebAssembly runs a full nodal analysis about 60 times a second. GPIO pins drive real nets, ADC inputs read solved node voltages, and probes report RMS, DC and current wherever you drop them.

Adders, comparators, decoders, flip-flops and a 1-bit ALU slice: no microcontroller anywhere, just gates, switches and LEDs solved as a real net. The classroom half of electronics, without the breadboard.

The M5Stack Cardputer with its keyboard, Seeed's round display keeping time, Pimoroni's Badger 2350 driving e-paper, and DFRobot's UNIHIKER M10 in the catalogue alongside them. Their makers sent the hardware so the emulation could be checked against the real thing.




35 boards across 6 CPU architectures — AVR8, ARM Cortex-M, ARM Cortex-A, RISC-V, Xtensa, and Linux. Including partner boards from Pimoroni, M5Stack, Seeed Studio and DFRobot. All running locally, no cloud needed.
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Private projects, BOM and schematic exports, GitHub Sync and the offline desktop app, for everyone enrolled.
Billed once to your institution, per semester or per year. Volume pricing on request for large cohorts.
Arduino, ESP32, RP2040, STM32, ATtiny and Raspberry Pi, with SPICE analog solved alongside the firmware. Not a sandboxed mock.
The simulator stays free forever. Paid plans unlock the Linux and STM32 boards, WiFi and the offline desktop app. Maker and Pro add the AI agent; No AI leaves it out.
Discover the simulator + light AI help.
The full workbench, zero AI. You write every line.
For makers shipping real circuits with AI help.
Private projects, GitHub Sync and BOM exports.
Questions, bugs and ideas: the Discord and the issue tracker are open, and so is every line of the simulator.
An interactive ESP32 circuit simulation you can run free in your browser on Velxio, by bmw550i.
#include <WiFi.h>
#include <esp_now.h>
#include <ArduinoJson.h>
//#include <LittleFS.h>
#include "config.h"
// Diese Funktion wird im echten setup() ganz oben aufgerufen
void initSerial() {
Serial.begin(115200);
delay(500); // Kurze Pause, damit der Serielle Monitor bereit ist
Serial.println("--- System startet ---");
}
// Globale Konfigurationsinstanz
SystemConfig sysCfg;
// Speicher für die aktuellen Werte ALLER bekannten IDs (lokal & remote)
// Im Echtbetrieb empfiehlt sich hier ein dynamischeres Mapping, für die Übersichtlichkeit nutzen wir feste ID-Zustände.
struct IdState {
uint16_t id;
int16_t value;
};
IdState globalRegistry[20];
uint8_t registryCount = 0;
// Helfer: Wert einer ID aus der globalen Liste holen
int16_t getRegisterValue(uint16_t id) {
for (uint8_t i = 0; i < registryCount; i++) {
if (globalRegistry[i].id == id) return globalRegistry[i].value;
}
return 0; // Standardmäßig aus
}
// Helfer: Wert einer ID in der globalen Liste aktualisieren
void setRegisterValue(uint16_t id, int16_t value) {
for (uint8_t i = 0; i < registryCount; i++) {
if (globalRegistry[i].id == id) {
globalRegistry[i].value = value;
return;
}
}
if (registryCount < 20) {
globalRegistry[registryCount] = {id, value};
registryCount++;
}
}
void loadConfiguration() {
Serial.println(F("[DEBUG] Starte loadConfiguration()")); Serial.flush();
loadFallbackConfig();
// GPIOs für die Eingänge vorbereiten
Serial.printf("[DEBUG] Bearbeite %d Eingaenge...\n", sysCfg.inputCount); Serial.flush();
for (uint8_t i = 0; i < sysCfg.inputCount; i++) {
Serial.printf("[DEBUG] Eingang %d: ID=%d, PinA=%d, PinB=%d\n", i, sysCfg.inputs[i].id, sysCfg.inputs[i].pinA, sysCfg.inputs[i].pinB); Serial.flush();
if (sysCfg.inputs[i].pinA < 48) { // Gültige ESP32-S3 Pins prüfen
pinMode(sysCfg.inputs[i].pinA, INPUT_PULLUP);
} else {
Serial.printf("[WARNUNG] Ungueltiger PinA (%d) an Eingang Index %d!\n", sysCfg.inputs[i].pinA, i); Serial.flush();
}
if (sysCfg.inputs[i].pinB != 255 && sysCfg.inputs[i].pinB < 48) {
pinMode(sysCfg.inputs[i].pinB, INPUT_PULLUP);
}
}
// PWM für die Ausgänge vorbereiten
Serial.printf("[DEBUG] Bearbeite %d Gruppen-Ausgaenge...\n", sysCfg.groupCount); Serial.flush();
for (uint8_t g = 0; g < sysCfg.groupCount; g++) {
Serial.printf("[DEBUG] Gruppe %d: ID=%d, OutputPin=%d\n", g, sysCfg.groups[g].groupId, sysCfg.groups[g].outputPin); Serial.flush();
if (sysCfg.groups[g].outputPin != 255 && sysCfg.groups[g].outputPin < 48) {
Serial.println(F("[DEBUG] Setze pinMode OUTPUT")); Serial.flush();
pinMode(sysCfg.groups[g].outputPin, OUTPUT);
//Hier Fehler XXX
Serial.print("g ");
Serial.println(g);
Serial.print(