Simulation Limits

Circzy runs real firmware on emulated microcontrollers, so most programs behave exactly as on hardware. A few things are different.

Speed

The emulators run in your browser. Programs that spend most of their time in delay() run at real speed, because the emulator skips the idle time. Programs that loop continuously without pausing make the emulator execute every instruction; on a slower computer, ESP32 and Pico programs of that kind can fall behind real time. The timer in the simulation panel always shows the simulated time, so time-based calculations in your program stay correct.

Networking

ESP32/ESP8266 WiFi connects to the Circzy virtual network, not to a real radio. HTTP/HTTPS requests to the internet are forwarded by the Circzy server, the MQTT broker runs in the browser, and NTP time comes from your computer clock. Raw TCP connections other than HTTP and MQTT, WebSocket, BLE, ESP-NOW, and TLS certificates are not simulated. See WiFi & Virtual Phone.

Analog electronics

Circzy simulates digital logic and the analog values that sensors and potentiometers produce. It does not solve full analog circuits: currents, voltage drops across resistors, capacitor charging and transistor amplifiers are not calculated. Resistors are treated as connections, and LEDs light whenever their anode is driven higher than their cathode.

Hardware damage

Nothing can break: shorting pins, reversing polarity or connecting 5 V to a 3.3 V board has no effect in the simulator. Be careful when you build the same circuit for real.

Peripherals

Parts

Each part simulates the behavior that programs normally use. For example, the DHT22 answers with the temperature and humidity you set, and the HC-SR04 returns an echo for the distance you set. Rare modes of a chip that common libraries do not use may not be available.