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Expand Up @@ -3,56 +3,82 @@ title: What's the difference between UNO R3 and UNO R4 boards?
id: 9350551575964
---

Learn about the differences between UNO R3 and the new UNO R4 WiFi and UNO R4 Minima boards.
Learn about the differences between the Arduino UNO R3, UNO R4 Minima and UNO R4 WiFi boards.

---

## Select differences

Here are a few changes you may notice if you've previously used the UNO R3:

### USB connector type

UNO R4 boards use a **USB-C** connector.

You'll need a USB-C cable to connect the board to your computer.

### Different behavior on runtime errors
In this article:

If the board encounters a runtime error while running an uploaded sketch, you need to double-press the reset button to put it into bootloader mode before uploading a new sketch.

Note that unlike some Mbed OS boards, runtime errors do not result in a flashing LED.

### Differnet board package

All previous UNO boards (except the UNO WiFi Rev2) were AVR-based, and used the **Arduino AVR Boards** package.

To use the new UNO R4 boards, install the new **Arduino UNO R4 Boards** package.
- [Board overview](#overview)
- [Technical specifications comparison](#tech-specs)
- [FAQs](#faq)

---

## Does the UNO R4 replace the UNO R3?
## Board overview {#overview}

The UNO R4 boards maintain the same form factor, pinout and 5 V operating voltage as the UNO R3. Here's a quick overview:

- **UNO Rev3**: A classic board with an 8-bit architecture, offering straightforward functionality and broad library compatibility.

- **UNO R4 Minima**: Focused on simplicity, it offers essential functions ideal for prototyping and basic learning. It includes advanced features such as an SWD port for program debugging, along with increased processing power and additional memory.

- **UNO R4 WiFi**: Equipped with WiFi and Bluetooth connectivity, it is ideal for IoT and wireless projects. The Qwiic I2C Connector and 12x8 Red LED Matrix enable project creation without soldering, manual wiring, or using a breadboard.

## Technical specifications comparison {#tech-specs}

| Feature | Arduino UNO R3 | Arduino UNO R4 Minima | Arduino UNO R4 WiFi |
|--------------------------|:--------------------------------:|:-----------------------------:|:-----------------------------:|
| Microcontroller | ATmega328P | Renesas RA4M1 (Arm Cortex-M4) | Renesas RA4M1 (Arm Cortex-M4) |
| Wi-Fi/Bluetooth LE | No | No | ESP32-S3-MINI-1-N8 |
| USB Connector | USB-B | USB-C | USB-C |
| Mouse/keyboard emulation | No | Yes | Yes |
| Real-Time Clock | No | Yes | Yes |
| Built-in LED Pin | 13 | No | No |
| Digital I/O Pins | 14 | 14 | 14 |
| Analog input pins | 6 | 6 | 6 |
| PWM pins | 6 | 6 | 6 |
| DAC | No | 1 (12-bit) | 1 (12-bit) |
| External interrupts | No | 2,3 | 2,3 |
| UART | Yes | Yes | Yes |
| I2C | Yes | Yes | Yes |
| SPI | Yes | Yes | Yes |
| CAN | No | Yes | Yes |
| Qwiic connector | No | No | Yes |
| OFF pin | No | No | Yes |
| VRTC pin | No | No | Yes |
| LED matrix | No | No | 12x8 (96 red LEDs) |
| Operating voltage | 5V | 5V | 5V |
| Input voltage | 7-12V | 6-24V | 6-24V |
| DC current per I/O Pin | 20mA | 8mA | 8mA |
| Clock speed | 16MHz | 48MHz | 48MHz |
| Memory | 2kB SRAM, 32kB FLASH, 1kB EEPROM | 256kB Flash, 32kB RAM | 256kB Flash, 32kB RAM |
| MCU resolution | 8-bit | 32-bit | 32-bit |
| ADC resolution | 10-bit | 14-bit | 14-bit |

## FAQs {#faq}

### Does the UNO R4 replace the UNO R3?

No, the Arduino UNO R3 will still be available and supported for makers who want to work with its 8-bit AVR microcontroller.

---
### What board package should I install for the UNO R4?

## Compatibility
For UNO R4, install the **Arduino UNO R4 Boards** package. Previous UNO boards (except the UNO WiFi Rev2) were AVR-based, and used the **Arduino AVR Boards** package.

### Can I use hardware compatible with the UNO R3 with an UNO R4 board?

UNO R4 boards maintain the same mechanical and electrical compatibility, allowing you to seamlessly use your existing shields and hardware with the new board.

### Can I use my sketch developed for UNO R3 with an UNO R4 board?
> [!NOTE]
> Third-party UNO shields are compatible with R4 in terms of voltage and pinout. However, software compatibility might require some porting work, so it should be checked with shield manufacturers before purchase.

Yes, if your sketch was developed using the [Arduino API](https://docs.arduino.cc/language-reference/).
### Can I use my sketch developed for UNO R3 with an UNO R4 board?

If your sketch uses instructions specific to the AVR architecture, they will have to be changed to ensure compatibility.
Yes, if your sketch was developed using the [Arduino API](https://docs.arduino.cc/language-reference/). If your sketch uses instructions specific to the AVR architecture, they will have to be changed to ensure compatibility.

### Are libraries for UNO R3 also compatible with the UNO R4 boards?

Libraries that are based on the [Arduino API](https://docs.arduino.cc/language-reference/) will work as is.
- Libraries that are based on the [Arduino API](https://docs.arduino.cc/language-reference/) will work as is.

Libraries that use AVR-specific instructions are not compatible with the architecture of UNO R4 boards. However, there are libraries that have already been ported as part of our early adopters program.
- Libraries that use AVR-specific instructions are not compatible with the architecture of UNO R4 boards. However, some of these libraries have already been ported. For more details, refer to the [UNO R4 Library Compatibility repository](https://github.com/arduino/uno-r4-library-compatibility).

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