Arduino UNO R4 – A Versatile and Powerful IoT Development Board

Product Review: Arduino UNO R4 Read our in-depth review of the Arduino UNO R4, the latest addition to the UNO series. Discover its powerful 32-bit Renesas microcontroller, Wi-Fi connectivity, and integrated LED matrix. Learn about its pros and cons for IoT applications and maker projects.

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The Arduino UNO R4 is the latest addition to the UNO board series by Arduino, bringing significant upgrades and features to the popular prototyping board. With a 32-bit Renesas microcontroller, Espressif ESP32-S3 module, one-click cloud connectivity, and an integrated 12×8 red LED matrix, the UNO R4 offers enhanced capabilities for makers and IoT enthusiasts.

One of the notable improvements in the UNO R4 is the integration of the RA4M1 processor from Renesas, which provides a 32-bit microcontroller with increased clock speed, memory, and flash storage compared to its predecessor. Powered by an Arm Cortex-M4 core running at 48 MHz, the RA4M1 microcontroller delivers higher processing power for more complex projects. With 32 kB of SRAM and 256 kB of flash memory, the UNO R4 provides ample space for storing code and data. The inclusion of a floating-point unit (FPU) in the Cortex-M4 core further enhances the performance of certain applications.

In terms of connectivity, the UNO R4 offers options for both Wi-Fi and non-Wi-Fi versions. The Wi-Fi version incorporates the Espressif ESP32-S3 module, enabling seamless Wi-Fi and Bluetooth Low Energy connectivity for IoT applications. Additionally, the board features a 12×8 red LED matrix, which can be used for creative projects involving animations or displaying sensor data without the need for additional hardware.

Arduino has taken care to maintain compatibility with the existing UNO ecosystem while introducing new features. The pinout, voltage, and form factor remain unchanged from the UNO R3, ensuring seamless integration with existing shields and projects. The addition of a USB-C port, increased power supply voltage to 24 V, and improved thermal design further enhance the board’s usability and robustness.

The UNO R4 provides ample I/O capabilities, including a CAN bus, two SPI, and two I2C serial ports. This allows users to connect multiple shields and execute different tasks in parallel, minimising wiring complexity. Furthermore, the board includes a 12-bit analog DAC and an operational amplifier, expanding the range of applications and sensor integration possibilities.

The Arduino UNO R4 demonstrates a commitment to the Arduino community by incorporating feedback and requests from users. The board’s compatibility with existing shields, libraries, examples, and projects ensures a smooth transition for developers and makes it easier to leverage the extensive resources available within the community.

Cloud connectivity is a standout feature of the UNO R4 Wi-Fi version, allowing data upload and synchronization between multiple Arduinos. The Arduino Cloud integration simplifies communication between boards without the need for complex radio protocols or additional code. This feature opens up possibilities for creating interconnected projects with ease.

Another noteworthy addition is the real-time clock (RTC), which allows the board to retain time even when powered off. With the RTC pin and an external buffer battery, users can keep the clock running independently, conserving power when the board is turned off.

The UNO R4 Minima variant offers a cost-effective option for makers seeking increased processing power without additional features. With HID over USB capability, users can simulate a mouse or keyboard, enabling quick and innovative interface designs.

Overall, the Arduino UNO R4 represents a significant milestone in the UNO series. The board combines enhanced processing power, connectivity options, and a rich set of features while maintaining compatibility with existing hardware and software resources. With the inclusion of Wi-Fi, the integrated LED matrix, and seamless cloud connectivity, the UNO R4 is well-suited for a wide range of IoT applications and creative projects.


  1. Increased Processing Power: The incorporation of the Renesas RA4M1 microcontroller with a 32-bit Arm Cortex-M4 core provides a significant boost in processing power, allowing for more complex and demanding projects.
  2. Versatility and Compatibility: The UNO R4 maintains compatibility with the existing UNO ecosystem, including shields, libraries, and projects, making it easy for developers to transition and leverage the extensive resources available within the Arduino community.
  3. Wi-Fi Connectivity: The UNO R4 Wi-Fi version with the Espressif ESP32-S3 module enables seamless Wi-Fi and Bluetooth Low Energy connectivity, making it ideal for IoT applications and wireless communication.
  4. Integrated LED Matrix: The built-in 12×8 red LED matrix adds a visual element to projects, enabling the display of animations and sensor data without the need for additional hardware.
  5. Cloud Connectivity: The one-click cloud connectivity feature allows for easy data upload and synchronization between multiple Arduinos, simplifying communication and enabling the creation of interconnected projects.


  1. Limited Memory: While the UNO R4 offers increased memory compared to its predecessor, the available SRAM (32 kB) and flash memory (256 kB) might still be limiting for very large-scale or memory-intensive projects.
  2. Lack of Advanced Features: Although the UNO R4 provides significant improvements over the UNO R3, it may not offer the same level of advanced features and capabilities as some other development boards in the market targeted specifically at maker/pro communities.

Overall, the Arduino UNO R4 is a versatile and powerful development board that brings notable improvements to the UNO series. While it offers enhanced processing power, compatibility, and connectivity options, it is important to consider the memory limitations.

For more information about the Arduino UNO R4, visit Arduino’s official website.

The Arduino UNO R4 is a top contender for makers, hobbyists, and professionals looking to explore and innovate in the IoT space.

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