> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/wokwi/wokwi-docs/llms.txt
> Use this file to discover all available pages before exploring further.

# wokwi-arduino-uno

> Arduino Uno R3 board reference - the most popular Arduino board powered by the ATmega328p chip

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:

<ParamField path="0" type="Serial (USART)">
  RX - Serial receive
</ParamField>

<ParamField path="1" type="Serial (USART)">
  TX - Serial transmit
</ParamField>

<ParamField path="2" type="External interrupt">
  INT0
</ParamField>

<ParamField path="3" type="External interrupt">
  INT1
</ParamField>

<ParamField path="10" type="SPI">
  SS (Chip select)
</ParamField>

<ParamField path="11" type="SPI">
  MOSI
</ParamField>

<ParamField path="12" type="SPI">
  MISO
</ParamField>

<ParamField path="13" type="SPI">
  SCLK (Clock)
</ParamField>

<ParamField path="A4" type="I2C">
  SDA (Data)
</ParamField>

<ParamField path="A5" type="I2C">
  SCL (Clock)
</ParamField>

### 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:

```cpp theme={null}
pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, HIGH);
```

See [Blink](https://wokwi.com/projects/344891652101374548) 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](https://github.com/wokwi/avr8js). 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](https://wokwi.com/projects/309372800631571009) |
| 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](../gdb-debugging)                |

Legend:\
✔️ Simulated\
🟡 Simulated, but see notes\
❌ Not implemented

If you need any of the missing features, please [open an issue on the AVR8js repo](https://github.com/wokwi/avr8js/issues/new) or [reach out on Discord](https://wokwi.com/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](../guides/serial-monitor). 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](../guides/libraries).

## Simulator examples

* [Arduino Blink](https://wokwi.com/projects/344891652101374548)