***__Important note:__ The Nano R4 operates at +5 VDC natively. When connecting sensors or modules that operate at +3.3 VDC, make sure to verify voltage compatibility to avoid component damage.***

- **Via USB-C connector**: The most common method during development and programming

- **Via `VIN` pin**: Using an external +6-21 VDC power supply that will be internally regulated to +5 VDC

- **Via `5V` pin**: Directly connecting a regulated +5 VDC source (with caution)

***__Important note:__ The Nano R4's `VIN` pin accepts a voltage range of +6-21 VDC. Do not connect voltages outside this range as you could permanently damage the board. Always verify all the connections before applying power.***

The Nano R4 also includes an onboard +3.3 VDC regulator ([AP2112K](https://www.diodes.com/assets/Datasheets/AP2112.pdf)) that provides power for the following:

- **Qwiic connector**: Supplies +3.3 VDC power to connected I²C devices

- **I²C level translation**: Enables communication between the +5 VDC microcontroller and +3.3 VDC Qwiic devices

- **Internal +3.3 VDC peripherals**: Powers certain internal circuits that require +3.3 VDC operation

This internal +3.3 VDC supply allows the board to interface with both +5 VDC and +3.3 VDC devices through the Qwiic ecosystem while maintaining the +5 VDC operation of the board's main microcontroller.

The Nano R4 board features built-in I²C (Inter-Integrated Circuit) communication that allows your projects to communicate with multiple devices using just two wires. I²C is implemented within the RA4M1 microcontroller and uses two dedicated pins to provide reliable serial communication with sensors, displays, memory modules and other microcontrollers. This makes it perfect for projects that need to connect several devices without using many pins.

I²C is particularly useful when your project needs to communicate with multiple sensors and devices in a simple way, rather than using complex wiring. While SPI is excellent for high-speed communication and UART for basic serial data exchange, I²C excels at connecting many devices with minimal wiring. Multiple I²C devices can share the same two-wire bus, each with its own unique address, making it ideal for sensor networks, display modules and expandable systems.

The Nano R4's I²C interface offers the following technical specifications:

| **Parameter** | **Value** | **Notes** |

|:-----------------:|:-------------:|:--------------------------:|

| Clock Speed | Up to 400 kHz | Standard/Fast mode |

| Data Transfer | 8-bit | Standard data width |

| Communication | Half-duplex | One direction at a time |

| I²C Pins | `A4`, `A5` | SDA, SCL respectively |

| Device Addressing | 7-bit/10-bit | Up to 127 unique addresses |

| Operating Voltage | +5 VDC | Same as board |

| Pull-up Resistors | Internal | Built-in weak pull-ups |