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: B3.14.0
// ===================================================================
// 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
// B3.5.1: Muss vor den von Arduino/Velxio erzeugten Funktionsprototypen
// vollstaendig definiert sein. ActionTargetType kommt aus config.h.
struct ResolvedActionTarget {
bool valid;
ActionTargetType type;
uint16_t targetId;
int16_t index;
uint8_t deviceType;
};
// ===================================================================
// B3.11.0: TEMPORAL RULE GATES
// ===================================================================
// Zeitfenster gehoeren zur Rule-Eignung, bleiben aber von den bestehenden
// Condition-Baeumen getrennt. Dieses Overlay ist bewusst runtime-only; die
// Config-/JSON-Struktur wird in B3.11.0 noch nicht erweitert.
struct RuleTemporalGate {
bool valid;
uint16_t ruleId;
bool enabled;
uint16_t startMinute;
uint16_t endMinute;
uint8_t weekdayMask;
};
#define MAX_RULE_TEMPORAL_GATES 32
RuleTemporalGate ruleTemporalGates[MAX_RULE_TEMPORAL_GATES];
uint8_t ruleTemporalGateCount = 0;
#define WDT_TIMEOUT_SECONDS 5
#define SKETCH_CODE_VERSION "B3.14.0"
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)
// ===================================================================
// B3.8.2i - CHUNKED CONFIG IMPORT
// ===================================================================
// Der Browser zerlegt grosse JSON-Dateien in kleine HTTP-Requests.
// Der ESP32 sammelt die Chunks in einer temporaeren LittleFS-Datei und
// uebernimmt die Config erst nach erfolgreicher Vollstaendigkeits- und
// JSON-Pruefung beim COMMIT. Der Chunk-Index macht Wiederholungen eines
// bereits akzeptierten Chunks idempotent, falls der Proxy die Antwort
// verliert und der Browser denselben Chunk erneut sendet.
#define IMPORT_CHUNK_SIZE 400
#define IMPORT_TEMP_FILE "/config.import.tmp"
#define IMPORT_SESSION_ID_MAX 48
static bool importChunkActive = false;
static String importChunkSessionId;
static uint16_t importChunkExpected = 0;
static uint16_t importChunkTotal = 0;
static uint32_t importChunkTotalBytes = 0;
static uint32_t importChunkReceivedBytes = 0;
static uint16_t importChunkLastIndex =