Running the Simulation

Starting and stopping

Press the green ▶ button in the simulation panel. Circzy:

Sends your sketch (or the code generated from your blocks) to the compile server.
Compiles it with the official core for your board.
Loads the firmware into the emulator and starts the board.

The status in the panel header shows each stage:

Status	Meaning
Ready	Nothing is running.
Compiling...	The compile server is building your program. If other programs are compiling at the same time, the status shows your position in the queue.
Running	The board is executing your program.
Failed	Compilation failed. The Compilation Error panel explains why.

Press ■ to stop. The timer next to the status shows the simulated time since the program started.

The ⋮ button next to ▶ opens:

Item	Effect
Restart	Starts the program again from the beginning while the simulation is running. The cached build is reused, so it restarts quickly.
Show / Hide Serial Monitor	Opens or closes the Serial Monitor.
Mute / Unmute sound	Turns the sound of buzzers and speakers on or off.

Interacting with the circuit

While the simulation runs you can operate inputs directly on the canvas:

Part	Interaction
Push buttons	Press and hold with the mouse.
Slide switch, tilt sensor, PIR	Click to toggle.
Potentiometer	Drag the knob.
Slide potentiometer	Drag the slider.
Keypads, joystick, rotary encoder, rotary dialer, DIP switch	Click their keys, switches or controls.
IR remote	Click a button; the IR receiver in the circuit picks up the code.
HC-05 Bluetooth	Select it and type a message in Send from phone.
RFID reader	Click the reader to tap or remove the card. Set the card UID in the toolbar.

Sensors that measure the environment are adjusted from the toolbar: select the part and move its sliders. For example, a DHT22 has temperature and humidity sliders, an HC-SR04 has a distance slider and a photoresistor has a light-level slider. Your program reads the new value immediately.

The Parts Reference lists the controls of every part.

Outputs

Outputs update live:

LEDs light up with brightness that follows PWM.
Displays (LCD, OLED, TFT, 7-segment, LED matrix, NeoPixel) show what your program draws.
Servos and stepper motors turn, DC motors spin and relays click.
Buzzers play tones through your speakers unless the sound is muted.
The board's built-in LED and power LED behave like the real ones.

Changing the circuit while running

While the program compiles or runs, the circuit is locked: parts cannot be moved, rotated, recolored, added or deleted, and wires and diagram.json cannot be changed. The canvas hint shows circuit locked. You can still operate the circuit: press buttons, flip switches, turn knobs and move sensor sliders in the toolbar. Stop the simulation to edit the circuit, then press ▶ again. To start again from a clean state without editing, use Restart.

Simulated time

The emulators run your program instruction by instruction. Programs that wait with delay() run at real speed. Programs that loop without any pause make the emulator work continuously, and on a slower computer they can fall behind real time; the timer always shows the simulated time. See Simulation Limits.

Ready to try it?

Start simulating free