Arduino in 2026: Uno R4, Uno Q, Nano, and Which Board to Buy

The Arduino lineup now splits into three clear paths. The UNO R4 is the 5V workhorse for shields and learning. The Nano R4 shrinks that same silicon into a breadboard-ready module. The UNO Q adds a Linux-capable processor next to a real-time microcontroller. This guide compares all three, shows the code and wiring you need to get started, and ends with a buying decision you can act on today.

Quick Takeaways

• Buy the UNO R4 Minima or WiFi for learning, shields, and classic 5V projects.
• Buy the Nano R4 for compact builds and low-cost production prototypes.
• Buy the UNO Q when you need Linux, a camera, or edge AI next to real-time I/O.
• Prices move. The UNO Q’s listed price has shifted by region and memory variant, so check the store before you order.

The 2026 Arduino Lineup at a Glance

Arduino now sells three distinct classes of board, and each solves a different problem.

Class 1: classic microcontrollers. The UNO R4 Minima, UNO R4 WiFi, and Nano R4 all share one chip. The Renesas RA4M1 is a 32-bit Arm Cortex-M4 at 48MHz. Sketches move between them with minimal changes.

Class 2: hybrid MPU + MCU. The UNO Q runs Debian Linux on one processor and Arduino sketches on another. It is a different kind of product, not a faster Uno.

Class 3: legacy. The UNO R3 (ATmega328P, 8-bit, 16MHz) is still everywhere in tutorials, but new designs should start on an R4.

Arduino UNO R4: The Default Choice

The UNO R4 keeps the UNO footprint, pinout, and 5V logic. Your existing shields still fit. The core upgrade is the RA4M1, which brings 256KB of flash, 32KB of SRAM, and 8KB of EEPROM. That is 8x the flash and 16x the SRAM of the ATmega328P.

UNO R4 Minima vs. UNO R4 WiFi

Both boards use the same RA4M1. The WiFi variant adds an ESP32-S3 coprocessor, a 12×8 LED matrix, and a Qwiic connector.

Electrical Limits to Know Before You Wire

• GPIO current: The R4 sources or sinks a maximum of 8mA per pin. The R3 allowed 20mA. Drive LEDs through a transistor or a MOSFET, or use a current-limiting resistor sized for under 8mA.
• Logic level: 5V. Level-shift when connecting 3.3V sensors.
• Analog: 6 analog inputs at up to 14-bit resolution, plus a 12-bit DAC on A0.
• Buses: 1x UART, 1x I2C, 1x SPI, and 1x CAN (needs an external transceiver).
• Library caveat: Some UNO R3 libraries use AVR-specific instructions and will not compile on the R4. Check library support before porting.

Code Example: Read a Sensor at 14-Bit

// Arduino UNO R4 (Minima or WiFi)
// Reads an analog sensor at 14-bit resolution and prints volts.

const int SENSOR_PIN = A1;       // Analog input on A1
const float VREF = 5.0;          // R4 ADC reference is 5V
const int ADC_BITS = 14;         // RA4M1 supports up to 14-bit ADC
const float ADC_MAX = 16383.0;   // 2^14 - 1

void setup() {
  Serial.begin(115200);          // UART over USB-C
  analogReadResolution(ADC_BITS); // Raise ADC from default 10-bit to 14-bit
}

void loop() {
  int raw = analogRead(SENSOR_PIN);       // 0 to 16383
  float volts = (raw / ADC_MAX) * VREF;   // Convert counts to volts
  Serial.print("Raw: ");
  Serial.print(raw);
  Serial.print("  Volts: ");
  Serial.println(volts, 4);               // Four decimal places
  delay(250);
}

Arduino Nano R4: The Compact, Cheap Option

The Nano R4 puts the same RA4M1 into a tiny 4.3 x 1.7cm module. It comes in two versions: with headers for breadboards, and without headers for soldering onto a carrier board. Launch pricing was $13.30 with headers and $12.10 without.

Sketches written for the UNO R4 Minima are directly compatible. The board also adds a few things the Minima lacks:

• A dedicated Qwiic connector plus an extra 5V I2C port
• 8 analog inputs and 21 digital I/O pins
• A 12-bit DAC on A0 and op-amp access on A1, A2, A3
• An RTC with an external 32.768kHz crystal and backup battery access
• Castellated pads for direct PCB mounting

The Nano R4 has no wireless. If you need Wi-Fi in a Nano footprint, look at the Nano ESP32 instead.

Nano R4 vs. UNO R4 Minima

Arduino UNO Q: Linux and Real-Time Control on One Board

Arduino announced the UNO Q on October 7, 2025. It pairs two processors in the UNO form factor.

• MPU: Qualcomm Dragonwing QRB2210, quad-core Arm Cortex-A53 at 2.0GHz, with an Adreno GPU and dual ISPs (13MP + 13MP, or 25MP at 30fps). It runs Debian Linux.
• MCU: STM32U585, Arm Cortex-M33 at up to 160MHz, with 2MB flash and 786KB SRAM. It runs Arduino sketches on Zephyr OS.

The two sides talk over a Bridge RPC layer, managed through Arduino App Lab. App Lab adds “Bricks” for AI, web, and integrations. The MPU handles vision, AI, and networking. The MCU handles timing-critical I/O.

UNO Q Specifications

Heads-Up Before You Wire

The UNO Q’s STM32U585 is a 3.3V part, and the Qwiic bus is 3.3V. Treat the UNO Q as a 3.3V board unless the official pinout says otherwise for a specific header pin. Do not assume classic 5V UNO shield behavior. Verify each shield against the board documentation before connecting it.

Pricing Note

Prices differ by source and over time. Retailers have listed the 2GB UNO Q anywhere from about $45 to $59, and the official US store listed the 2GB model at $59. The 4GB/32GB variant costs more. Check current pricing before you buy.

UNO Q vs. Raspberry Pi 5

The Pi 5 wins on raw compute. The UNO Q wins when you want deterministic I/O and Linux in one board without wiring a second microcontroller.

Which Arduino Should You Buy?

Match the board to the job, not to the newest launch.

Skip the UNO Q if your project is a blinking LED, a servo, or a temperature logger. The R4 does it for less, with simpler tooling and lower power draw.

Real-World Project: Wi-Fi Temperature Logger on the UNO R4 WiFi

This build reads a DS18B20 temperature sensor and publishes readings over Wi-Fi.

Parts

• Arduino UNO R4 WiFi
• DS18B20 digital temperature sensor
• 4.7kΩ pull-up resistor
• Breadboard and jumper wires

Wiring

Firmware

// UNO R4 WiFi: DS18B20 temperature over HTTP-style serial log
// Libraries: OneWire, DallasTemperature, WiFiS3 (built in)

#include <OneWire.h>
#include <DallasTemperature.h>
#include <WiFiS3.h>

#define ONE_WIRE_PIN 2             // DQ on D2

OneWire oneWire(ONE_WIRE_PIN);
DallasTemperature sensors(&oneWire);

const char* SSID = "YOUR_WIFI";    // Replace with your network
const char* PASS = "YOUR_PASSWORD";

void setup() {
  Serial.begin(115200);
  sensors.begin();                 // Start DS18B20 bus

  Serial.print("Connecting to Wi-Fi");
  WiFi.begin(SSID, PASS);          // ESP32-S3 handles the radio
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("IP: ");
  Serial.println(WiFi.localIP());  // Confirm network connection
}

void loop() {
  sensors.requestTemperatures();               // Trigger conversion
  float tempC = sensors.getTempCByIndex(0);    // Read first sensor

  if (tempC != DEVICE_DISCONNECTED_C) {
    Serial.print("Temp (C): ");
    Serial.println(tempC, 2);
  } else {
    Serial.println("Sensor not found. Check DQ wiring and pull-up.");
  }
  delay(2000);                                  // Sample every 2 seconds
}

Troubleshooting

1. Reads -127°C: The sensor is not responding. Check the 4.7kΩ pull-up on DQ.
2. Wi-Fi never connects: Confirm a 2.4GHz network and correct credentials.
3. Compile error on a library: The library may use AVR-only code. Look for an R4-compatible fork.

Protect Your Board from Common Failures

• Do not drive loads from a GPIO pin. On the R4, each pin is limited to 8mA. Use a MOSFET (such as an IRLZ44N for logic-level gate drive) for motors and relays.
• Add a flyback diode across inductive loads like relays and motors.
• Level-shift 3.3V devices. Connecting a 3.3V sensor’s data line directly to a 5V R4 pin can damage the sensor.
• Use a real supply for the UNO Q. Provide 5V at up to 3A over USB-C, or 7-24V on VIN, so the MPU does not brown out under load.
• Isolate mains-adjacent circuits. Use an optocoupler or a certified relay module between the board and anything connected to line voltage.

Frequently Asked Questions

Is the Arduino UNO R4 better than the UNO R3?

Yes, for most new projects. The R4 uses a 32-bit RA4M1 at 48MHz with 256KB flash and 32KB SRAM, versus the R3’s 8-bit ATmega328P at 16MHz. The tradeoff is a lower 8mA pin current limit and occasional library incompatibility.

What is the Arduino UNO Q used for?

The UNO Q suits projects that need Linux and real-time control together. Typical uses include edge vision, local AI inference, robotics, and IoT gateways. The QRB2210 handles compute and the STM32U585 handles timing-critical I/O.

Can I use my old Arduino shields on the UNO R4 and UNO Q?

UNO R4 boards keep the UNO R3 form factor, pinout, and 5V logic, so most shields work. The UNO Q uses the UNO footprint but runs a 3.3V MCU, so check each shield’s voltage compatibility before use.

Does the Nano R4 have Wi-Fi?

No. The Nano R4 has no wireless hardware. For wireless in a Nano-sized board, use a different Nano variant such as the Nano ESP32.