wokwi-arduino-uno Reference
Arduino Uno is the most popular board in the Arduino family. It is powered by the ATmega328p chip, which has 32K bytes of Flash program memory, 2k bytes of SRAM and 1K bytes of EEPROM.
Pin names
Pins 0 to 13 are digital GPIO pins. Pins A0 to A5 double as analog input pins, in addition to being digital GPIO pins.
There are three ground pins: GND.1, which is on top of the board, next to pin 13, and GND.2/GND.3, which are on the bottom.
Pins VIN / 5V are connected to the positive power supply.
Pins 3.3V / IOREF / AREF / RESET are not available in the simulation.
Digital pins 3, 5, 6, 9, 10, and 11 have hardware PWM support.
Some of the digital pins also have additional functions:
| Pin | Function | Signal |
|---|---|---|
| 0 | Serial (USART) | RX |
| 1 | Serial (USART) | TX |
| 2 | External interrupt | INT0 |
| 3 | External interrupt | INT1 |
| 10 | SPI | SS (Chip select) |
| 11 | SPI | MOSI |
| 12 | SPI | MISO |
| 13 | SPI | SCLK (Clock) |
| A4 | I2C | SDA (Data) |
| A5 | I2C | SCL (Clock) |
On board LEDs
The board includes four LEDs:
| LED | Function |
|---|---|
| L | Connected to digital pin 13 |
| RX | Serial RX Activity |
| TX | Serial TX Activity |
| ON | Power LED. Always on while the simulation is running |
In general, only the "L" LED can be controlled by the user's code. You can use the LED_BUILTIN constant to reference it from your code:
pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, HIGH);
See Blink for a complete code example.
Attributes
| Name | Description | Default value |
|---|---|---|
| frequency | MCU clock frequency, in hertz. Common values: "8m", "16m", and "20m" * | "16m" |
* Many Arduino libraries assume 16 MHz clock frequency. Changing the clock frequency will void your warranty!
Simulation features
The Arduino Uno is simulated using the AVR8js Library. The table below summarizes the status of features:
| Peripheral | Status | Notes |
|---|---|---|
| Processor | ✔️ | |
| GPIO | ✔️ | Including External/Pin Change Interrupts |
| 8-bit timers | ✔️ | Timer0, Timer2 |
| 16-bit timer | ✔️ | Timer1 |
| Watchdog Timer | ✔️ | Usage example |
| USART | ✔️ | |
| SPI | 🟡 | Master mode only |
| I2C | 🟡 | Master mode only |
| EEPROM | ✔️ | |
| Clock Prescale | ✔️ | |
| ADC | ✔️ | Used by analogRead() |
| Analog Comparator | ❌ | |
| GDB Debugging | ✔️ | See the GDB Debugging Guide |
Legend:
✔️ Simulated
🟡 Simulated, but see notes
❌ Not implemented
If you need any of the missing features, please open an issue on the AVR8js repo or reach out on Discord.
Serial Monitor
You can use the Serial Monitor to receive information from your Arduino code, such as debug print. You can also use it to send information to your code, such as textual commands.
For more information and code samples, check out the Serial Monitor guide. It also explains how to configure the Serial monitor, e.g. set the line ending characters.
Libraries
The simulator supports many popular Arduino libraries. For a complete list, see the Libraries guides.