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.
An interactive ESP32 circuit simulation you can run free in your browser on Velxio, by hichemsystem1.
/* =============================================================================
* ATS-ESP32-IMPL-001
* ESP32 AUTOMATIC TRANSFER SWITCH CONTROLLER - STEG / GENERATOR
*
* DESIGNER ENGINEER : Hichem Souki
*
* ---------------------------------------------------------------------------
* ARDUINO IDE SETTINGS
* ---------------------------------------------------------------------------
* Board : "ESP32 Dev Module"
* Partition scheme : "Huge APP (3MB No OTA / 1MB SPIFFS)"
* (required: Wi-Fi + classic Bluetooth in one image)
* Flash size : 4 MB
* Upload speed : 921600 (drop to 115200 if uploads fail)
* Core Debug Level : None
*
* LIBRARIES (Library Manager)
* - Adafruit SSD1306
* - Adafruit GFX Library
* - RTClib (Adafruit)
*
* All other headers come with the ESP32 Arduino core.
*
* COMPILATION
* Put every file of this folder in one sketch directory named exactly
* ATS_ESP32_Controller. Open ATS_ESP32_Controller.ino and press Verify.
*
* ---------------------------------------------------------------------------
* SAFETY - NON NEGOTIABLE
* ---------------------------------------------------------------------------
* - Mechanical interlock between KM1 and KM2 : MANDATORY.
* - Hardwired NC cross-interlock in both coil circuits : MANDATORY.
* - This firmware is NOT the protection against source paralleling.
* - No mains voltage on any ESP32 pin. Ever.
* - VERIFY THE COIL VOLTAGE PRINTED ON BOTH CONTACTORS BEFORE ENERGIZING.
* - Final mains connection and energization by a qualified electrician.
* ===========================================================================*/
#include "Config.h"
#include "Types.h"
#include "Settings.h"
#include "Io.h"
#include "Faults.h"
#include "Transfer.h"
#include "GenIface.h"
#include "AtsCore.h"
#include "Clock.h"
#include "Ui.h"
#include "Net.h"
#include <Wire.h>
#include <esp_task_wdt.h>
static uint32_t s_lastScan = 0;
/* ---------------------------------------------------------------------------
* Watchdog helper - compatible with ESP32 Arduino core 2.x and 3.x
* -------------------------------------------------------------------------*/
static void watchdogBegin() {
#if defined(ESP_ARDUINO_VERSION_MAJOR) && (ESP_ARDUINO_VERSION_MAJOR >= 3)
esp_task_wdt_config_t cfg = {
.timeout_ms = WDT_TIMEOUT_S * 1000U,
.idle_core_mask = 0,
.trigger_panic = true
};
esp_task_wdt_reconfigure(&cfg);
#else
esp_task_wdt_init(WDT_TIMEOUT_S, true);
#endif
esp_task_wdt_add(NULL);
}
/* ===========================================================================
* SETUP
* ===========================================================================*/
void setup() {
Serial.begin(115200);
delay(50);
Serial.println();
Serial.println(F("=============================================="));
Serial.printf (" %s %s (%s)\n", FW_NAME, FW_VERSION, FW_DOC