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 2023beec071.
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <math.h>
// =====================================================
// PIN DEFINITIONS
// =====================================================
#define SDA_PIN 9
#define SCL_PIN 8
#define BUZZER_PIN 16
#define SOS_BUTTON_PIN 17
#define FALL_BUTTON_PIN 18
// =====================================================
// I2C ADDRESSES
// =====================================================
#define MPU6050_ADDR 0x68
#define OLED_ADDR 0x3C
// =====================================================
// OLED
// =====================================================
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(
SCREEN_WIDTH,
SCREEN_HEIGHT,
&Wire,
-1
);
// =====================================================
// MPU6050 REGISTERS
// =====================================================
#define PWR_MGMT_1 0x6B
#define ACCEL_CONFIG 0x1C
#define GYRO_CONFIG 0x1B
#define ACCEL_XOUT_H 0x3B
// =====================================================
// FALL DETECTION THRESHOLDS
// =====================================================
// Acceleration in g
#define FALL_ACCEL_THRESHOLD 2.0
// Gyroscope in deg/s
#define FALL_GYRO_THRESHOLD 200.0
// =====================================================
// MPU6050 VARIABLES
// =====================================================
int16_t accelX;
int16_t accelY;
int16_t accelZ;
int16_t gyroX;
int16_t gyroY;
int16_t gyroZ;
float ax;
float ay;
float az;
float gx;
float gy;
float gz;
float totalAcceleration;
float totalGyro;
// =====================================================
// I2C WRITE
// =====================================================
void writeMPU(byte reg, byte value)
{
Wire.beginTransmission(MPU6050_ADDR);
Wire.write(reg);
Wire.write(value);
Wire.endTransmission();
}
// =====================================================
// I2C READ
// =====================================================
void readMPU(byte reg, byte *buffer, byte length)
{
Wire.beginTransmission(MPU6050_ADDR);
Wire.write(reg);
Wire.endTransmission(false);
Wire.requestFrom(
MPU6050_ADDR,
length
);
for (byte i = 0; i < length; i++)
{
if (Wire.available())
{
buffer[i] = Wire.read();
}
else
{
buffer[i] = 0;
}
}
}
// =====================================================
// INITIALIZE MPU6050
// =====================================================
void initializeMPU()
{
Serial.println("Initializing MPU6050...");
// Wake sensor
writeMPU(PWR_MGMT_1, 0x00);
delay(100);
// Accelerometer ±8g
writeMPU(ACCEL_CONFIG, 0x10);
// Gyroscope ±500 deg/s
writeMPU(GYRO_CONFIG, 0x08);
delay(100);
Serial.println("MPU6050 READY!");
}
// =====================================================
// READ MPU6050
// =====================================================
void readMPU6050()
{
byte data[14];
readMPU(
ACCEL_