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 raise the daily AI quota and unlock the Linux boards, private projects and the offline desktop app.
Discover the simulator + light AI help.
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.
group project fir exhibition
An interactive ESP32 circuit simulation you can run free in your browser on Velxio, by saketsuman5356.
#include <Arduino.h>
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>
// =====================================================
// PIN CONFIGURATION
// =====================================================
// ---------- GROVE 125KHz RFID ----------
#define RFID_RX 16
#define RFID_TX 17
// ---------- SD CARD ----------
#define SD_CS 14
#define SD_SCK 18
#define SD_MISO 19
#define SD_MOSI 23
// ---------- LCD ----------
#define LCD_SDA 21
#define LCD_SCL 22
// ---------- DHT11 ----------
#define DHT_PIN 26
#define DHT_TYPE DHT11
// ---------- OTHER SENSORS ----------
#define PIR_PIN 27
#define LDR_PIN 34
#define MQ135_PIN 35
// ---------- OUTPUTS ----------
#define BUZZER_PIN 25
#define GREEN_LED 32
#define RED_LED 33
// ---------- ESP32-CAM UART ----------
// Different pins so they do NOT conflict with RFID.
#define CAM_RX 13
#define CAM_TX 15
// =====================================================
// OBJECTS
// =====================================================
HardwareSerial RFIDSerial(1);
HardwareSerial CameraSerial(2);
LiquidCrystal_I2C lcd(0x27, 16, 2);
DHT dht(DHT_PIN, DHT_TYPE);
// =====================================================
// FUNCTION DECLARATIONS
// =====================================================
String readRFID();
void createAttendanceFile();
void saveAttendance(
String uid,
float temperature,
float humidity,
int ldr,
int mq135,
int pir
);
void readSensors(
float &temperature,
float &humidity,
int &ldr,
int &mq135,
int &pir
);
void successSignal();
void errorSignal();
void cameraCapture(String uid);
void showReady();
// =====================================================
// SETUP
// =====================================================
void setup() {
// USB Serial Monitor
Serial.begin(115200);
delay(500);
Serial.println();
Serial.println("================================");
Serial.println(" SMART ATTENDANCE SYSTEM");
Serial.println("================================");
// ===================================================
// GROVE RFID
// ===================================================
// 9600 baud, 8 data bits, no parity, 1 stop bit
RFIDSerial.begin(
9600,
SERIAL_8N1,
RFID_RX,
RFID_TX
);
Serial.println("Grove RFID initialized");
// ===================================================
// ESP32-CAM SERIAL
// ===================================================
CameraSerial.begin(
115200,
SERIAL_8N1,
CAM_RX,
CAM_TX
);
Serial.println("Camera serial initialized");
// ===================================================
// OUTPUT PINS
// ===================================================
pinMode(BUZZER_PIN, OUTPUT);
pinMode(GREEN_LED, OUTPUT);
pinMode(RED_LED, OUTPUT);
digitalWrite(BUZZER_PIN, LOW);
digitalWrite(GREEN_LED, LOW);
digital