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 circuit simulation you can run free in your browser on Velxio, by melimelum586.
#include <Wire.h> // for I2C
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <RTClib.h> // for rtc
#include <Adafruit_NeoPixel.h> // for led strip
// pins
const int plusBtn = 12;
const int centerBtn = 14;
const int minusBtn = 27;
const int alarmLED = 13;
const int ledStripPin = 18;
const int NUM_LEDS = 60;
// add-ons
Adafruit_SSD1306 display(128, 64, &Wire, -1); // ширина, висота, використовуємо I2C (обмін даних по двох сигнальних дротах - SDA(передаємо дані), SCL (зчитуємо дані), немає окремого пін для ресет у дісплея
RTC_DS3231 rtc;
Adafruit_NeoPixel strip(NUM_LEDS, ledStripPin, NEO_GRB + NEO_KHZ800);
// center btn vars
bool lastCenterBtnState = HIGH;
bool centerBtnState = 1;
bool centerPressed = false;
// plus btn vars
bool lastPlusBtnState = HIGH;
bool plusBtnState = 1;
bool plusPressed = false;
unsigned long plusPressStart = 0;
unsigned long lastPlusChange = 0;
// screens
bool alarmScreen = false;
bool setAlarmScreen = false;
bool clearAlarmScreen = false;
// minus btn state
bool minusBtnState = 1;
bool lastMinusBtnState = HIGH;
bool minusPressed = false;
unsigned long minusPressStart = 0;
unsigned long lastMinusChange = 0;
// alarm vars
unsigned long alarmStartTime = 0;
int setAlarmHour = 6;
int setAlarmMinute = 0;
int alarmEditStep = 0;
int alarmHour = 0;
int alarmMinute = 0;
int ledHour = 0;
int ledMinute = 0;
bool alarmEnabled = false;
bool clearAlarmScreen = false;
bool noYesBtns = false; // no - false, yes - true for underline
bool alarmeTrigged = false;
bool show24 = true;
unsigned long secAlarm = -1;
unsigned long nowSecTime = -1;
unsigned long timeToSec(int hour = -1, int minute = -1, int second = -1);
unsigned long secLED = -1;
void setup() {
Wire.begin();
display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
rtc.begin();
strip.begin();
Serial.begin(9600);
display.clearDisplay();
display.setTextSize(2);
display.setTextColor(SSD1306_WHITE);
pinMode(plusBtn, INPUT_PULLUP);
pinMode(centerBtn, INPUT_PULLUP);
pinMode(minusBtn, INPUT_PULLUP);
pinMode(alarmLED, OUTPUT);
delay(1000);
lastCenterBtnState = digitalRead(centerBtn);
lastPlusBtnState = digitalRead(plusBtn);
lastMinusBtnState = digitalRead(minusBtn);
}
void loop() {
// check center btn
// 1 = HIGH = NOT pressed
// 0 = LOW = pressed
/*DateTime now = rtc.now();
if (alarm && now.hour() == alarmHour && now.minute() == alarmMinute && now.second() == 0 && !alarmeTrigged) {
alarmeTrigged = true;
alarmStartTime = millis();
}
if (alarmeTrigged && millis() - alarmStartTime >= 10000) {
digitalWrite(alarmLED, LOW);
alarmeTrigged = false;
}*/
nowSecTime = timeToSec();
if (alarmEnabled && nowSecTime == secLED && !alarmeTrigged) {
for (int i = 0; i < NUM_LEDS; i++) {
strip.setPixelColor(i, strip.Color(255, 255, 255));
}
strip.show();
}
if (alarmEnabled && nowSecTime == secAlarm && !alarmeTrigged) {
alarmeTrigged = true;
alarmStartTime = millis();
}
if (