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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.




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An interactive Arduino Uno circuit simulation you can run free in your browser on Velxio, by dave.
// Estación Meteorológica
// Sensores: DHT22 (Temperatura + Humedad) y BMP280 (Presión + Temp)
// Pantalla: LCD 1602 (modo 4-bit)
// Conexiones:
// LCD RS -> pin 12
// LCD E -> pin 11
// LCD D4 -> pin 5
// LCD D5 -> pin 4
// LCD D6 -> pin 3
// LCD D7 -> pin 2
// LCD V0 -> potenciómetro (contraste)
// DHT22 DATA -> pin 7
// BMP280 SDA -> A4 (I2C)
// BMP280 SCL -> A5 (I2C)
#include <LiquidCrystal.h>
#include <DHT.h>
#include <Wire.h>
#include <Adafruit_BMP280.h>
// Definición de pines
#define DHTPIN 7
#define DHTTYPE DHT22
// Pines LCD
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
// Sensores
DHT dht(DHTPIN, DHTTYPE);
Adafruit_BMP280 bmp; // I2C (dirección 0x76 o 0x77)
// Variables de tiempo
unsigned long lastSensorRead = 0;
const long sensorInterval = 2000; // Leer sensores cada 2s
unsigned long lastDisplayUpdate = 0;
const long displayInterval = 3000; // Cambiar pantalla cada 3s
int displayPage = 0; // 0: Temp+Humi, 1: Presión+Altitud
void setup() {
Serial.begin(9600);
Serial.println(F("=== Estación Meteorológica Iniciada ==="));
lcd.begin(16, 2);
lcd.clear();
lcd.print(F(" Estacion "));
lcd.setCursor(0, 1);
lcd.print(F(" Meteorologica"));
delay(2000);
dht.begin();
if (!bmp.begin(0x76)) {
Serial.println(F("BMP280 no encontrado en 0x76, probando 0x77..."));
if (!bmp.begin(0x77)) {
Serial.println(F("ERROR: BMP280 no encontrado!"));
lcd.clear();
lcd.print(F("BMP280 ERROR!"));
while (1);
}
}
// Configuración BMP280
bmp.setSampling(Adafruit_BMP280::MODE_NORMAL,
Adafruit_BMP280::SAMPLING_X2, // Temperatura
Adafruit_BMP280::SAMPLING_X16, // Presión
Adafruit_BMP280::FILTER_X16,
Adafruit_BMP280::STANDBY_MS_500);
Serial.println(F("Sensores listos!"));
lcd.clear();
}
void loop() {
unsigned long now = millis();
// Leer sensores cada 2 segundos
if (now - lastSensorRead >= sensorInterval) {
lastSensorRead = now;
leerSensores();
}
// Cambiar página en LCD cada 3 segundos
if (now - lastDisplayUpdate >= displayInterval) {
lastDisplayUpdate = now;
displayPage = (displayPage + 1) % 2;
actualizarLCD();
}
}
// Variables globales para almacenar lecturas
float tempDHT = 0.0;
float humedad = 0.0;
float tempBMP = 0.0;
float presion = 0.0;
float altitud = 0.0;
bool lecturaExitosa = false;
void leerSensores() {
// Leer DHT22
float h = dht.readHumidity();
float t = dht.readTemperature();
// Leer BMP280
float tb = bmp.readTemperature();
float p = bmp.readPressure() / 100.0F; // hPa
float a = bmp.readAltitude(1013.25); // Altitud aprox, ref 1013.25 hPa
// Verificar lecturas
if (isnan(h) || isnan(t)) {
Serial.println(F("Error leyendo DHT22"));
lecturaExitosa = false;
} else {
tempDHT = t;
humedad = h;
tempBMP = tb;
presion = p;
altitud = a