Arduino Uno R4 WiFi
The Arduino Uno R4 WiFi pairs a Renesas RA4M1 ARM Cortex-M4 at 48MHz with an onboard ESP32-S3 for WiFi and BLE 5.0, plus a 12x8 LED matrix and CAN bus support. It is the first official Arduino Uno with wireless connectivity, bridging Arduino's beginner-friendly ecosystem with modern IoT capabilities.
Best for Arduino loyalists who want WiFi without leaving the Uno ecosystem, skip if you need raw ESP32-S3 performance.
Where to Buy
Pros
- WiFi and BLE 5.0 via onboard ESP32-S3 — first official Uno with wireless
- 12x8 red LED matrix built into the board for visual output without wiring
- CAN bus support — rare in hobby boards, valuable for automotive and industrial projects
- Full Arduino Uno shield compatibility — thousands of existing shields work directly
- USB-C with native USB for HID device emulation
Cons
- 48MHz ARM Cortex-M4 main processor is far slower than the ESP32-S3 it carries as a coprocessor
- Only 32KB SRAM and 256KB flash — severely limiting compared to ESP32 boards
- The ESP32-S3 coprocessor is not directly programmable — it handles WiFi/BLE only
- 68.85 x 53.34mm is large compared to Nano-format alternatives
The Dual-Processor Architecture
The Uno R4 WiFi has an unusual design: a Renesas RA4M1 (ARM Cortex-M4 at 48MHz) runs your Arduino sketch, while a separate ESP32-S3 handles WiFi and BLE communication. Your code runs on the M4 and talks to the ESP32-S3 through an internal serial bridge.
This means you cannot directly access the ESP32-S3's dual-core 240MHz processor, 8MB PSRAM, or camera interface. If you want the full ESP32-S3, the Arduino Nano ESP32 gives you direct access to the S3 in a smaller form factor.
Arduino Ecosystem Compatibility
The R4 WiFi maintains the classic Uno form factor and pinout, so the thousands of Arduino shields designed over the past decade remain compatible. This backward compatibility is the board's strongest advantage — no other WiFi-enabled board offers this depth of accessory ecosystem.
The Arduino IDE, Arduino Cloud, and the massive library repository all support the R4 WiFi natively. For beginners and educators, this means every Arduino tutorial and course works with minor adaptations. The 12x8 LED matrix adds a visual output that beginners can program without any wiring.
Connectivity and I/O
WiFi 802.11 b/g/n and BLE 5.0 are handled by the ESP32-S3 coprocessor. The Arduino WiFiS3 library provides a familiar API. CAN bus support via a dedicated peripheral is notable — most hobby boards require an external MCP2515 module for CAN communication.
The 20 GPIO pins, 6 ADC channels, and 1 DAC channel are adequate for typical Arduino projects. USB-C with native USB support enables HID device emulation for keyboard and mouse projects. The 6-24V input voltage range makes it easy to power from various sources.
Full Specifications
Processor
| Specification | Value |
|---|---|
| Architecture | ARM Cortex-M4 |
| CPU Cores | 1 |
| Clock Speed | 48 MHz |
| coprocessor | ESP32-S3 (WiFi/BLE) |
Memory
| Specification | Value |
|---|---|
| Flash | 0.256 MB |
| SRAM | 32 KB |
| eeprom | 8 KB |
Connectivity
| Specification | Value |
|---|---|
| WiFi | 802.11 b/g/n |
| Bluetooth | 5.0 |
I/O & Interfaces
| Specification | Value |
|---|---|
| GPIO Pins | 20 |
| ADC Channels | 6 |
| dac_channels | 1 |
| SPI | 1 |
| I2C | 1 |
| UART | 2 |
| USB | USB-C (native) |
| can_bus | 1x CAN bus |
| led_matrix | 12x8 red LED matrix |
Power
| Specification | Value |
|---|---|
| Input Voltage | 6-24 V |
| operating_voltage | 5 V |
Physical
| Specification | Value |
|---|---|
| Dimensions | 68.85 x 53.34 mm |
| Form Factor | Arduino Uno (shield-compatible) |
Who Should Buy This
Arduino IDE is the standard for education. WiFi enables cloud projects. The LED matrix provides instant visual feedback. Shield compatibility means existing lab kits work.
Built-in CAN bus is rare in hobby boards. WiFi sends diagnostic data to a phone app. Arduino libraries for OBD-II are mature.
The 48MHz M4 is the bottleneck — the ESP32-S3 coprocessor only handles WiFi/BLE, not your application code. An ESP32-S3-DevKitC gives you the full 240MHz dual-core for your logic.
Better alternative: ESP32-S3-DevKitC-1
Works well with Arduino shield displays and WiFi. But 32KB SRAM limits complex web dashboards. An ESP32-S3 with 512KB SRAM handles this more comfortably.
Better alternative: ESP32-S3-DevKitC-1
Frequently Asked Questions
Can I program the ESP32-S3 on the Uno R4 WiFi directly?
Not in the standard Arduino workflow. The ESP32-S3 runs WiFi/BLE firmware and communicates with the RA4M1 via a serial bridge. For direct ESP32-S3 programming, use the Arduino Nano ESP32 instead.
Arduino Uno R4 WiFi vs ESP32-S3: which should I choose?
Choose the Uno R4 WiFi for shield compatibility, Arduino ecosystem, education, and CAN bus. Choose the ESP32-S3-DevKitC for raw performance (5x faster CPU), camera support, 8MB PSRAM, and direct access to all ESP32-S3 features.
Does the Uno R4 WiFi work with existing Arduino shields?
Yes. It maintains the classic Uno R3 pin layout and 5V logic level. Most shields designed for any Arduino Uno will work physically and electrically. Check individual shield library compatibility with the RA4M1 processor.
What is the LED matrix for?
The 12x8 red LED matrix is built into the board and controlled via the Arduino LED_Matrix library. It can display scrolling text, simple animations, icons, and sensor readings without any external display or wiring.
Can the Uno R4 WiFi do Bluetooth?
Yes. The ESP32-S3 coprocessor provides BLE 5.0. Use the ArduinoBLE library for BLE peripheral and central roles. Bluetooth Classic is not supported — only BLE.