Seeeduino XIAO (SAMD21) Simulator
the original XIAO, with its real DAC
Simulate the Seeeduino XIAO (SAMD21) online for free: Arduino sketches on an in-browser Cortex-M0+ engine, a real 10-bit DAC on A0, native USB serial, and GPIO, I2C and SPI on a live canvas.
Free plan · No install, no account · Runs in your browser
Seeeduino XIAO (SAMD21) at a glance
The original XIAO is a SAMD21 Cortex-M0+ at 48 MHz with native USB and a real 10-bit DAC on A0. The in-browser engine boots the firmware the Seeed SAMD core produces; Serial is the USB CDC port, and analogWrite(A0, ...) drives the DAC rather than a PWM, which is what the board does on the bench and what the oscilloscope on the canvas shows.
- Processor
- SAMD21G18, Cortex-M0+ at 48 MHz
- Memory
- 32 KB SRAM · 256 KB flash
- Emulation
- samd21js (in-browser)
- Languages
- Arduino C++
- Plan
- Free
What you can do with the Seeeduino XIAO (SAMD21) simulator
The board on the canvas is the real thing as far as your code is concerned: the same pins, the same buses, the same peripherals, wired to the same 100+ sensors, displays and actuators every other Velxio board talks to.
A real DAC
analogWrite on the DAC pin drives a true voltage, not a PWM, so the oscilloscope and the SPICE parts downstream see the waveform the board really produces.
Arduino C++ sketches
Write a sketch in the Monaco editor with library completion, compile it against the board's own Arduino core and run the real firmware binary. The Serial Monitor is the USB port.
GPIO, PWM and ADC
Drive LEDs, relays and servos, read buttons and potentiometers, dim with PWM. Every pin follows the board's real pin map, so what works here works on the hardware.
I2C, SPI and UART
Talk to OLEDs, IMUs, ADCs, RTCs and SD cards over the buses the board really has. Bus traffic runs through emulated peripherals, not through a shortcut.
Serial Monitor
USB CDC serial reaches the Serial Monitor at the sketch's baud rate, with input, timestamps and a plotter.
XIAO footprint
The thumbnail-sized XIAO pinout: D0 to D10 with the I2C, SPI and UART pads where every XIAO has them, so projects move between XIAO boards with a pin map check.
SPICE analog parts
Op-amps, transistors, regulators and passives simulate in real time with ngspice in the browser; the board's pins drive them and read the solved voltages back.
Seeeduino XIAO (SAMD21) examples
Ready-to-run projects for this board from the gallery. Open one, read the sketch, press Run.
Seeeduino XIAO: BlinkBlink an LED on D1 and count on the serial monitor - the first thing to try on the Seeeduino XIAO, running on its own in-browser engine.
Seeeduino XIAO: OLED over I2CWrite text to a 128x64 SSD1306 on the Seeeduino XIAO's I2C pads (D4/D5) with U8g2, and mirror it on the serial monitor.
Seeeduino XIAO: Knob and buttonRead a potentiometer on D0 and a pull-up button on D2 of the Seeeduino XIAO; the button lights the LED and both values print on the serial monitor.
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Frequently asked questions
- Does analogWrite on A0 really produce a voltage?
- Yes. On the SAMD21 A0 is the DAC output, and the simulator drives a true voltage into the SPICE circuit, so a filter or an amplifier downstream sees the waveform.
- Can I use the Seeeduino XIAO as a USB device?
- Serial over USB CDC reaches the Serial Monitor. Other USB device classes (HID, MIDI) are not modelled.
- Is the Seeeduino XIAO free to simulate?
- Yes. It runs on the free plan, with no install and no account required.
- Is the Seeeduino XIAO (SAMD21) simulator free?
- Yes. The Seeeduino XIAO (SAMD21) runs on the free plan: open the editor, place the board and press Run. No install and no account are needed, and Velxio's editor and simulator core are open source under the GNU AGPLv3.
- Which languages can I use on the Seeeduino XIAO (SAMD21)?
- Arduino C++. The language is switched from the toolbar; the circuit on the canvas stays the same.
Ready to simulate the Seeeduino XIAO (SAMD21)?
Open the editor, place the Seeeduino XIAO (SAMD21) from the picker, wire what you need and press Run.
Launch the Seeeduino XIAO (SAMD21) simulator →