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.
An interactive ESP32-S3 circuit simulation you can run free in your browser on Velxio, by user_00.
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <ESP32Servo.h>
// ============================================================
// PINS
// ============================================================
#define TRIG_PIN 5
#define ECHO_PIN 18
#define SDA_PIN 8
#define SCL_PIN 9
// Arm servo
#define ARM_SERVO_PIN 6
// Sorting servo
#define SORTING_SERVO_PIN 7
// CAM UART
#define CAM_RX 16
#define CAM_TX 17
// ============================================================
// DISTANCE SETTINGS
// ============================================================
// Waste detected below/equal to 50 cm
#define STOP_DISTANCE 50.0
// Robot is allowed to resume only after object is farther
// than this distance. This prevents repeated triggering.
#define RESUME_DISTANCE 55.0
// ============================================================
// MOTOR DRIVER
// Grove I2C Motor Driver with L298
// ============================================================
#define MOTOR_DRIVER_ADDR 0x0F
#define MOTOR_SPEED_SET 0x82
#define MOTOR_DIRECTION_SET 0xAA
// M1 clockwise, M2 anticlockwise
#define FORWARD_DIRECTION 0x06
#define MOTOR_SPEED 80
// ============================================================
// LCD
// ============================================================
LiquidCrystal_I2C lcd(
0x27,
16,
2
);
// ============================================================
// SERVOS
// ============================================================
Servo armServo;
Servo sortingServo;
// Small/minimal arm movement
#define ARM_HOME 45
#define ARM_PICK 70
// Small sorting movements
#define SORT_HOME 90
#define SORT_WET 65
#define SORT_DRY 80
#define SORT_PLASTIC 100
#define SORT_METAL 115
// ============================================================
// CAMERA UART
// ============================================================
HardwareSerial CamSerial(2);
// ============================================================
// ROBOT STATE
// ============================================================
enum RobotState
{
SEARCHING,
PROCESSING,
WAITING_CLEAR
};
RobotState robotState = SEARCHING;
// ============================================================
// MOTOR STATE
// Prevents repeatedly sending I2C commands
// ============================================================
bool motorsRunning = false;
// ============================================================
// MOTOR SPEED
// ============================================================
void setMotorSpeed(
byte motor1,
byte motor2
)
{
Wire.beginTransmission(
MOTOR_DRIVER_ADDR
);
Wire.write(
MOTOR_SPEED_SET
);
Wire.write(motor1);
Wire.write(motor2);
Wire.endTransmission();
}
// ============================================================
// MOTOR DIRECTION
// ============================================================
void setMotorDirection(
byte direction
)
{
Wire.beginTransmission(
MOTOR_DRIVER_ADDR
);
Wire.write(