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.

Open the editor

Your firmware, on an emulated CPU

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.

Open the editor

Analog that is solved, not faked

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.

SPICE simulator

Digital logic, gate by gate

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.

Digital examples

The partner boards, emulated for real

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.

See every board

Sketch code

from lcd_api import LcdApi import time class I2cLcd(LcdApi): def __init__(self, i2c, i2c_addr, num_lines, num_columns): self.i2c = i2c self.i2c_addr = i2c_addr self.backlight = 0x08 super().__init__(num_lines, num_columns) time.sleep_ms(50) self._write4bits(0x03); time.sleep_ms(5) self._write4bits(0x03); time.sleep_ms(5) self._write4bits(0x03); time.sleep_ms(1) self._write4bits(0x02) self.hal_write_command(0x2C) # 4 bits, 4 lines, 5x8 font self.hal_write_command(0x0C) # display on, cursor off self.clear() def hal_write_command(self, cmd): self._send(cmd & 0xF0, 0) self._send((cmd << 4) & 0xF0, 0) def hal_write_data(self, data): self._send(data & 0xF0, 1) self._send((data << 4) & 0xF0, 1) def _write4bits(self, value): self._send(value, 0) def _send(self, data, mode): buf = bytes([data | mode | self.backlight | 0x04]) self.i2c.writeto(self.i2c_addr, buf) self.i2c.writeto(self.i2c_addr, bytes([data | mode | self.backlight])) time.sleep_us(50)

Arduino, ESP32 & Raspberry Pi.
Right in your browser.

Hardware partners

Real silicon. Real physics. One canvas.

Arduino, running the sketch you wrote

Your firmware, on an emulated CPU

Analog that is solved, not faked

Digital logic, gate by gate

The partner boards, emulated for real

Every architecture.
One tool.

Bring Velxio into your course.

Pro for every student

One predictable bill

The tools they will use at work

Free to run circuits. Pay for the AI.

Connect with the open source community

CASAHOST Smart Home ESP32 — ESP32 simulation

Components

Sketch code

More projects by yenihandresk