After the Arduino GIGA R1 and the Portenta C33, the latest announcement in the Arduino new-board frenzy is the Arduino UNO R4. Expected to be available late May 2023, the UNO R4 is the long-awaited update of the UNO R3. Or is it?

The Arduino UNO, initially released in 2010, has probably been the most successful Arduino board to date. Revision R3 has remained unchanged for about a decade and may therefore be considered rather stable. Then...
Arduino Uno R4

What to Expect From the Arduino UNO R4?

Well, about the only thing that seems to remain the same on the UNO is its name. Where the R3 is based on the 8-bit ATmega328 from Microchip, the R4 sports a RA4M1 32-bit ARM Cortex-M4 from Renesas running at 48 MHz instead of 16 MHz. It has 32 KB RAM, which is sixteen times more than the R3, and it has 256 KB of flash memory, which is eight times more than the R3. The ‘huge’ USB-B connector of the R3 has been replaced by a modern USB-C port. The maximum input voltage has gone up to 24 V, as it did on the new GIGA R1. The R4 also has a CAN bus and an extra SPI port.

Finally, there is a real analog output as the RA4M1 integrates a 12-bit DAC.


Even though the new processor is housed in a 64-pin package, the MCU on the R3 has 28 pins, the number of I/O ports has remained unchanged (20). This is because the R3 and R4 have identical shapes. The I/O on the R4 is also 5 V, therefore most extension shields should be able to work with the R4.

Who Is It For?

Not a lot of information has been released, and no price indication has been given yet. The Arduino UNO R4 will be available in two versions, the ‘WiFi’ with an ESP32-S3 module, and the ‘Minima’.

The R4 feels more like an update of the Arduino Zero, which, with its 32-bit ARM Cortex-M0 runs at the same clock frequency and has the same amount of memory. The Arduino RP2040 Nano Connect is much smaller in size, but not so much in resources, and it also features Wi-Fi.

The picture showing the board on the blog post has a big yellow rectangle covering almost 25% of the board space. Maybe an ATmega328 is hiding underneath?