Arduino Nano R4 vs UNO R4 Minima: Same RA4M1, Different Board

The Arduino Nano R4 and Arduino UNO R4 Minima are built around the same Renesas RA4M1 microcontroller.

At first glance, that makes them look almost interchangeable:

But the board-level implementation is very different.

The Nano R4 is designed for compact embedded systems, breadboards and small carrier boards. The UNO R4 Minima is designed around the traditional UNO shield ecosystem, larger connectors and easier bench prototyping.

So the decision is not really about CPU performance. It is about form factor, expansion, power, connector layout and which extra board features matter.

Quick Comparison

Feature	Nano R4	UNO R4 Minima
Main MCU	Renesas RA4M1	Renesas RA4M1
CPU	48 MHz Arm Cortex-M4 + FPU	48 MHz Arm Cortex-M4 + FPU
Logic voltage	5 V	5 V
Flash	256 kB	256 kB
SRAM	32 kB	32 kB
Data memory	8 kB	8 kB
ADC	Up to 14 bit	Up to 14 bit
DAC	12 bit on A0	12 bit on A0
Op-amp	Yes	Yes
CAN	Yes, external transceiver required	Yes, external transceiver required
RTC	Yes	Yes
USB	Native USB-C	Native USB-C
Analog header pins	A0-A7	A0-A5
Main I²C	A4/A5	A4/A5
Extra I²C	Dedicated 3.3 V Qwiic bus	No dedicated Qwiic bus
RTC backup	Dedicated VBATT support	RTC available, but no Nano-style VBATT header position
VIN range	6-21 V	6-24 V
Barrel jack	No	Yes
ICSP header	No traditional UNO ICSP header	Yes
Primary ecosystem	Nano carriers/breadboards	UNO shields

Same RA4M1 Means the Core Computing Hardware Is Essentially the Same

Both boards use the Renesas:

which contains:

• 48 MHz Arm Cortex-M4 CPU;
• hardware floating-point unit;
• 256 kB Flash;
• 32 kB SRAM;
• 8 kB data Flash;
• DMA;
• 14-bit ADC;
• 12-bit DAC;
• CAN controller;
• RTC;
• USB 2.0 Full-Speed;
• operational amplifier;
• advanced timer hardware.

So for pure processor workloads, neither board has a fundamental speed advantage.

A calculation-heavy sketch that fits the same pin mapping should perform very similarly on both boards.

Same 5 V GPIO

Both Nano R4 and UNO R4 Minima operate in a 5 V logic environment.

This is a major advantage over many modern Nano-family boards.

It means both are comfortable with:

• older 5 V sensors;
• classic LCD modules;
• 5 V relay boards;
• 74HC logic at 5 V;
• legacy Arduino accessories.

This is one reason the RA4M1 platform is interesting: it provides a modern 32-bit CPU without forcing an existing 5 V project into a 3.3 V redesign.

Form Factor Is the Biggest Difference

The Nano R4 is extremely compact.

Arduino’s current mechanical drawing gives a PCB outline of approximately:

with the USB-C connector overhanging the top edge.

The UNO R4 Minima uses the traditional much larger UNO footprint.

This makes the Nano R4 much better for:

• breadboards;
• compact enclosures;
• embedded products;
• small custom carrier boards;
• space-constrained control systems.

UNO R4 Minima Is Better for Shields

UNO R4 Minima retains the traditional UNO shield header layout.

That gives it immediate mechanical compatibility with a huge ecosystem of:

• motor shields;
• relay shields;
• prototype shields;
• display shields;
• industrial interface shields.

Electrical compatibility is good because the board also uses 5 V logic.

Software compatibility still depends on the library because an old shield library may contain AVR-specific code.

Nano R4 Is Better for Breadboards and Custom PCBs

The Nano format places pins on two narrow rows that fit directly into a breadboard or socketed carrier.

This is often much cleaner than mounting a full UNO board inside a finished project.

Nano R4 is also available in variants intended for through-hole/castellated integration, making it more natural for custom PCBs.

Analog Inputs: Nano R4 Exposes Two More

UNO R4 Minima exposes:

Nano R4 exposes:

So Nano R4 gives you two additional analog-labelled header positions.

This can matter in projects with:

• multiple potentiometers;
• analog sensors;
• voltage-monitoring channels;
• multi-axis analog joysticks;
• instrumentation front ends.

Both Support 14-Bit ADC Operation

Both boards share the RA4M1 ADC architecture.

The default Arduino resolution remains lower for compatibility, but you can request:

and obtain a numerical result from:

Resolution does not guarantee 14-bit absolute accuracy. Grounding, reference voltage, noise and source impedance still matter.

Both Have the Same 12-Bit DAC on A0

Both boards expose the RA4M1 DAC on:

Example:

This creates a true analog voltage rather than PWM.

For audio experiments, control voltages and analog setpoints, the two boards are functionally very similar here.

Both Expose the RA4M1 Op-Amp

The operational amplifier uses:

on the R4 architecture.

This provides useful signal conditioning without always needing an external op-amp.

PWM Is Essentially the Same

Both boards expose six normal PWM positions:

Because the MCU and timer hardware are the same family, ordinary analogWrite() behaviour is broadly similar.

Low-level direct timer configuration still needs to follow the exact board/core mapping.

UART Mapping Is Familiar

Both use:

for the normal external hardware UART.

Use:

because both use native RA4M1 USB rather than a classic external USB-to-UART bridge.

SPI Is Familiar on Both Boards

The main SPI header pins are:

UNO R4 Minima additionally provides the familiar 6-pin ICSP-style SPI header used by many UNO shields.

Nano R4 expects you to use its Nano header/castellated layout instead.

CAN: Same Peripheral, Similar Header Mapping

Both boards provide the RA4M1 classic CAN controller.

Arduino currently documents CAN on:

for UNO R4 Minima and Nano R4.

An external transceiver is required on both boards.

The microcontroller pins are logic-level CAN controller signals; they are not CANH/CANL.

CAN Transceiver Requirement

The physical bus still needs:

For more detail on termination and transceiver selection, see our UNO R4 CAN bus guide.

Main I²C Bus Is the Same

Both boards use:

for the main Arduino I²C bus.

Use:

for conventional I²C peripherals.

Nano R4 Adds a Separate Qwiic Bus

This is one of the most important board-level differences.

Nano R4 includes a dedicated Qwiic connector operating at:

through a second hardware I²C bus.

That means you can have:

UNO R4 Minima has only the main A4/A5 bus and no onboard Qwiic connector.

Why the Second I²C Bus Is Useful

A separate bus helps with:

• 3.3 V Qwiic sensors;
• duplicate I²C addresses;
• keeping legacy 5 V I²C separate from modern 3.3 V sensors;
• reducing wiring complexity.

For sensor-heavy embedded systems, Nano R4 can actually be more convenient despite being much smaller.

Nano R4 Has Dedicated RTC Backup Access

Nano R4 exposes a dedicated RTC backup-power arrangement through its VBATT function.

Arduino documents a backup supply range of approximately:

This lets the RTC keep running while the main board supply is removed.

UNO R4 Minima has the same RA4M1 RTC peripheral but does not expose the same convenient Nano-style VBATT header arrangement.

RTC Software Is Otherwise Similar

Because the MCU is the same family, the RTC feature set is broadly similar:

• date;
• time;
• calendar operation;
• alarms.

See our UNO R4 RTC guide for the programming model.

Native USB on Both Boards

Both boards use native RA4M1 USB.

This enables:

• USB serial;
• programming;
• keyboard emulation;
• mouse emulation;
• other supported HID functions.

Neither depends on an ATmega16U2-style USB bridge like older UNO boards.

Both Use USB-C

Both Nano R4 and UNO R4 Minima use USB-C.

That means the connector choice is no longer a reason to prefer the larger UNO board.

Power Input Is Different

UNO R4 Minima is designed for easy benchtop/external supply use.

Arduino specifies:

and the board includes a barrel jack connected to VIN.

Nano R4 specifies:

and has no barrel jack.

UNO R4 Minima Is Easier to Power from a Wall Adapter

The barrel jack makes the Minima convenient when you already have:

• 9 V adapters;
• 12 V adapters;
• bench DC supplies with barrel leads;
• UNO enclosures designed around the jack.

Nano R4 is more naturally powered through USB-C, VIN pins or a custom carrier board.

UNO R4 Minima Has Traditional UNO Power/Control Headers

The UNO board exposes the familiar:

• IOREF;
• RESET;
• 3.3 V;
• 5 V;
• GND;
• VIN;
• AREF;
• ICSP header.

This matters for shields designed around the UNO mechanical standard.

Nano R4 Is Better for a Custom Product

If your final design is going inside a compact enclosure, the UNO board can be physically wasteful.

Nano R4 is a better embedded module when:

• PCB area matters;
• you want socketed or soldered integration;
• you do not need UNO shields;
• you want the second I²C/Qwiic bus;
• you want A6/A7;
• you need convenient RTC backup.

UNO R4 Minima Is Better for the Workbench

The larger board has practical advantages:

• easier probing;
• larger spacing around headers;
• barrel jack power;
• shield stacking;
• traditional ICSP access;
• clearer lab wiring.

For education and fast prototyping, physical size can be an advantage rather than a disadvantage.

Do They Run the Same Sketch?

Often, yes.

Code that uses:

can often be moved between the boards with only pin changes.

Where Porting Problems Appear

You need to review code that assumes:

• Nano-only A6/A7;
• Nano Qwiic/Wire1;
• UNO ICSP connector routing;
• specific physical header placement;
• direct low-level pin numbers;
• board-specific power or LED pins.

The MCU is the same, but the PCB is not.

Same CPU Does Not Mean Same Pin Mapping Everywhere

RA4M1 peripheral signals can be routed differently between boards.

When a library or application directly accesses Renesas port identifiers rather than Arduino pin names, always verify the exact board variant.

Portable code should use Arduino names such as:

rather than hard-coded RA4M1 port registers unless low-level access is truly required.

Nano R4 vs UNO R4 Minima for CAN

Functionally, there is little reason to prefer one CPU over the other because the controller is the same.

Choose based on:

• enclosure space;
• connector layout;
• transceiver board/carrier;
• power source;
• whether UNO shields matter.

Nano R4 vs UNO R4 Minima for Analog Projects

Nano R4 has the edge because it exposes:

• A6;
• A7;
• the same 14-bit ADC capability;
• the same 12-bit DAC;
• the same op-amp;
• a separate Qwiic bus that leaves A4/A5 free for other use.

UNO R4 Minima still provides an excellent analog feature set but exposes fewer Nano-style channels.

Nano R4 vs UNO R4 Minima for Existing Shields

UNO R4 Minima wins immediately if the project already uses an UNO shield.

Nano R4 requires:

• rewiring;
• a carrier board;
• an adapter PCB;
• or a completely different module arrangement.

Nano R4 vs UNO R4 Minima for Breadboards

Nano R4 is far more convenient because its two-row narrow package plugs directly into breadboards and compact carriers.

UNO R4 Minima is normally connected with jumper wires or shields rather than inserted directly into a standard breadboard.

Which One Should You Choose?

Requirement	Better fit
UNO shield compatibility	UNO R4 Minima
Compact enclosure	Nano R4
Breadboard use	Nano R4
Barrel-jack power	UNO R4 Minima
VIN up to 24 V	UNO R4 Minima
Two extra analog-labelled pins	Nano R4
Dedicated Qwiic connector	Nano R4
Separate 3.3 V I²C bus	Nano R4
Convenient RTC backup battery	Nano R4
Traditional ICSP header	UNO R4 Minima
Raw CPU performance	Essentially equal
ADC/DAC/CAN capability	Essentially equal at MCU level

Quick Reference

Final Thoughts

Nano R4 and UNO R4 Minima deliver almost the same processor capability because the heart of both boards is the same RA4M1.

So choosing between them is mostly a mechanical and connectivity decision.

Choose Nano R4 when the project needs:

• small size;
• breadboard compatibility;
• Qwiic;
• a second I²C bus;
• extra analog header positions;
• easy integration into a custom PCB.

Choose UNO R4 Minima when the project needs:

• UNO shields;
• traditional ICSP access;
• a barrel jack;
• 24 V VIN tolerance;
• large, easy-to-probe development hardware.

For detailed pin mappings, see our Nano R4 pinout guide and UNO R4 Minima pinout guide.