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.
DFRobot · M5Stack links on this page are affiliate links: a purchase through them earns Velxio a small commission at no extra cost to you.
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.
One institution contract gives every student in the class a full Pro account. No per-seat checkout, no card details in a classroom.
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.
Web-Log-Terminal: vollständige h-Ausgabe (Puffer 64), größere Anzeige und Stick-to-Bottom-Scroll-Logik.
An interactive ESP32 circuit simulation you can run free in your browser on Velxio, by bmw550i.
// Version: B3.6.1
// ===================================================================
// SKETCH.INO - TEIL 1 (Definitionen, Variablen & Prototypen)
// ===================================================================
#include <WiFi.h>
#include <WebServer.h>
WebServer server(80);
#include <esp_now.h>
#include <ArduinoJson.h>
#include <esp_task_wdt.h>
#include "esp_mac.h"
#include "config.h"
#include "webpage.h"
#include <stdarg.h>
#include <time.h>
#include <ArduinoOTA.h> // ✅ Neu für drahtlose Updates
#define WDT_TIMEOUT_SECONDS 5
#define SKETCH_CODE_VERSION "B3.6.1"
uint32_t myLocalSequenceNumber = 0;
uint32_t simSequenceCounter = 0;
bool logToSerialActive = true;
bool logToEspNowActive = false;
bool logToWebActive = true;
bool logEspNowTransmitInProgress = false; // Schutz gegen Log->TX->Log Rekursion
#define WEB_LOG_MAX_LINES 512
String webLogBuffer[WEB_LOG_MAX_LINES];
uint16_t webLogBufferIdx = 0;
uint32_t webLogSequence = 0; // Monotone Sequenznummer je Logzeile (fuer Browser-Inkrement-Abgleich)
struct MsgFingerprint { uint16_t srcId; uint32_t seqNum; };
#define MESH_HISTORY_SIZE 512
MsgFingerprint meshHistory[MESH_HISTORY_SIZE];
uint16_t meshHistoryIdx = 0;
unsigned long lastWifiCheckTime = 0;
const unsigned long wifiCheckInterval = 10000;
// Forward declarations fuer Arduino automatisch erzeugte Funktionsprototypen.
// Die vollstaendige Definition wird hier benoetigt, weil Velxio/Arduino
// Funktionsprototypen vor spaeteren Struct-Definitionen erzeugen kann.
struct SourceRecognitionState;
struct LogicState {
uint16_t id;
ScaledValue value;
bool valid;
};
extern LogicState logicStates[20];
extern uint8_t logicStateCount;
// ===================================================================
// B3.6 - CONTEXT
// ===================================================================
// Context liefert allgemeine Umgebungs-/Zeitinformationen fuer die Logic.
// Context ist read-only fuer Conditions: Regeln lesen den aktuellen Kontext,
// veraendern ihn aber nicht. Feiertag wird bis zur spaeteren Config-Schicht
// als Laufzeitflag gefuehrt; dadurch bleibt B3.6 unabhaengig von Persistenz.
enum LogicContextId : uint16_t {
CONTEXT_HOUR = 1,
CONTEXT_MINUTE = 2,
CONTEXT_WEEKDAY = 3, // Montag=1 ... Sonntag=7
CONTEXT_DAY = 4, // Tag des Monats 1...31
CONTEXT_MONTH = 5, // Monat 1...12
CONTEXT_HOLIDAY = 6, // 0/1
CONTEXT_NIGHT_MODE = 7 // 0/1
};
struct LogicContext {
bool valid;
uint8_t hour;
uint8_t minute;
uint8_t weekday;
uint8_t day;
uint8_t month;
bool holiday;
bool nightMode;
};
LogicContext logicContext = {false, 0, 0, 1, 1, 1, false, false};
// B3.6 Standard-Nachtfenster: 22:00 bis 05:59.
uint8_t contextNightStartHour = 22;
uint8_t contextNightEndHour = 6;
unsigned long contextLastUpdateMs = 0;
bool contextTimeSyncStarted = false;
// B3.6.1: Nicht blockierende SNTP-Initialisierung. Der Context darf erst
// dann al