Arduino Nano ESP32 vs Nano 33 IoT: ESP32-S3 vs SAMD21 + NINA

The Arduino Nano ESP32 and Arduino Nano 33 IoT are both compact Wi-Fi/Bluetooth Nano boards, but they use completely different system architectures.

Nano ESP32 is a native ESP32 board:

Nano 33 IoT splits those jobs between two chips:

That distinction affects almost everything: CPU performance, memory, USB, wireless software, analog features, MicroPython support and how much headroom the board has for modern IoT applications.

Quick Comparison

Feature	Nano ESP32	Nano 33 IoT
Main application MCU	ESP32-S3	ATSAMD21G18A
CPU	Dual-core Xtensa LX7	Arm Cortex-M0+
Maximum clock	240 MHz	48 MHz
Internal RAM	512 kB	32 kB
PSRAM	8 MB	None
Application Flash	16 MB external QSPI	256 kB
Logic voltage	3.3 V	3.3 V
Wi-Fi	Native ESP32-S3 Wi-Fi	Via NINA-W102
Bluetooth LE	Native ESP32-S3 BLE	Via NINA-W102
ESP-NOW	Yes	No normal application support
MicroPython	Officially supported	Not the board’s main current workflow
ADC	12-bit SAR ADC	12-bit SAMD21 ADC
True DAC	No	10-bit DAC on A0
USB	Native ESP32-S3 USB-C	Native SAMD21 USB over Micro-USB
Security chip	ESP32-S3 hardware security features	ATECC608A secure element
Arduino Cloud	Yes	Yes

Nano ESP32 Is a Single-MCU Wireless Architecture

The defining characteristic of Nano ESP32 is simplicity of architecture.

The ESP32-S3 directly handles:

• your sketch;
• Wi-Fi;
• Bluetooth LE;
• USB;
• GPIO;
• timers;
• ADC;
• network stacks.

There is no separate connectivity coprocessor sitting between your code and the radio.

Nano 33 IoT Is a Dual-Processor Architecture

Nano 33 IoT uses:

The NINA-W102 is itself an ESP32-based module, but your normal sketch does not run on it.

Instead, the SAMD21 communicates with NINA through an internal control/SPI interface.

Why the Architecture Difference Matters

On Nano ESP32, radio functionality is part of the same software environment as the application.

On Nano 33 IoT, wireless traffic passes through the NINA firmware layer.

This has advantages and disadvantages.

Nano 33 IoT Advantages

• the SAMD21 application remains separated from the radio processor;
• WiFiNINA provides a relatively simple high-level networking API;
• wireless firmware can be updated independently;
• the architecture was designed around Arduino Cloud security and the ATECC608A.

Nano ESP32 Advantages

• much lower architectural overhead;
• direct access to ESP32 networking features;
• ESP-NOW;
• native BLE stack access;
• far more memory;
• much faster CPU;
• full ESP32 ecosystem compatibility.

CPU Performance

Nano 33 IoT’s SAMD21 provides:

Nano ESP32 provides:

For networking-heavy or computationally demanding applications, Nano ESP32 has far more headroom.

Examples include:

• complex JSON handling;
• multiple network connections;
• encryption;
• web serving;
• audio buffers;
• larger state machines;
• machine-learning inference.

Memory Difference Is Even Bigger Than CPU Difference

Nano 33 IoT provides:

Nano ESP32 provides:

The difference is enormous.

Why 8 MB PSRAM Matters

PSRAM makes Nano ESP32 comfortable with workloads that are awkward or impossible on 32 kB SRAM:

• large image or display buffers;
• large JSON documents;
• audio buffers;
• large HTTP responses;
• MicroPython heaps;
• machine-learning models;
• web assets.

Nano 33 IoT needs much tighter memory discipline.

Wi-Fi Architecture

Nano ESP32

Wi-Fi is native to the ESP32-S3.

Your sketch can directly use the ESP32 networking stack for:

• HTTP;
• HTTPS;
• MQTT;
• UDP;
• TCP servers;
• OTA updates;
• ESP-NOW;
• mDNS;
• custom sockets.

Nano 33 IoT

Wi-Fi runs on NINA-W102.

The normal Arduino interface uses:

The SAMD21 sends commands to the radio module rather than running the Wi-Fi stack directly.

Bluetooth Architecture

Again, Nano ESP32 runs BLE natively on the application MCU.

Nano 33 IoT delegates BLE to NINA-W102.

For simple BLE peripherals, either architecture works.

For projects requiring deep control of the ESP32 BLE stack or integration with other ESP32-native features, Nano ESP32 is more flexible.

ESP-NOW

Nano ESP32 supports:

which can provide low-latency peer-to-peer communication between ESP32-family devices without a conventional Wi-Fi access point.

This is not a normal Nano 33 IoT application feature because the NINA module is running Arduino’s connectivity firmware rather than your custom ESP32 application.

MicroPython

Nano ESP32 is officially supported by Arduino as a MicroPython board.

Its memory configuration makes that practical:

Nano 33 IoT is primarily a C/C++ Arduino platform.

Even where alternative language runtimes exist, 32 kB RAM creates a much tighter environment.

USB: Both Have Native USB, but the Connectors Differ

Nano ESP32 uses:

Nano 33 IoT uses:

So unlike boards that use a simple USB-to-UART bridge, both application MCUs can directly participate in USB communication.

Native USB Applications

Nano 33 IoT’s SAMD21 is well suited to:

• USB serial;
• keyboard;
• mouse;
• MIDI;
• custom USB-device projects.

Nano ESP32 also supports native USB device applications through the ESP32-S3 architecture and adds integrated USB/JTAG debugging.

Debugging

Nano ESP32 supports out-of-the-box USB/JTAG debugging with no separate probe.

Nano 33 IoT exposes SWD test pads for the SAMD21, but the normal product workflow is not as integrated around onboard debugging as Nano ESP32.

GPIO Voltage

Both boards use:

and neither should receive 5 V logic directly on the GPIO.

This makes them electrically more similar to each other than to Nano R4, Nano Every or classic Nano.

UART

Both expose a conventional external UART on:

while USB serial remains separate.

For Nano 33 IoT:

Nano ESP32 follows the same high-level pattern.

I²C

Both use:

for the default external I²C bus.

Nano 33 IoT uses the SAMD21 SERCOM system internally and keeps onboard devices separated from the normal external user bus through board routing.

Nano ESP32 can remap I²C to many different GPIO through the ESP32-S3 GPIO matrix, although A4/A5 are the default Nano-compatible pins.

SPI

The familiar Nano SPI pins are preserved:

On Nano ESP32, the underlying GPIO matrix makes alternative routing possible.

On Nano 33 IoT, SPI routing is tied more closely to SAMD21 SERCOM configuration.

Analog Input

Both boards offer eight analog-labelled positions:

but the ADC architectures are different.

Nano 33 IoT

The SAMD21 provides a 12-bit ADC.

A0-A7 map to SAMD21 ADC channels.

Arduino also notes that A4/A5 carry I²C pull-ups, so they are not ideal choices for precision analog measurement.

Nano ESP32

ESP32-S3 also provides 12-bit SAR ADC hardware.

The current Nano ESP32 mapping is:

For Wi-Fi-heavy analog projects, A0-A3 are the safer default because ADC2 has more resource-sharing constraints.

Nano 33 IoT Has a True DAC

This is one area where the older board has a real hardware advantage.

Nano 33 IoT provides:

Nano ESP32 has no true voltage DAC because ESP32-S3 removed the original ESP32’s internal DAC peripheral.

If You Need Analog Output

Nano 33 IoT can directly generate an analog voltage on A0.

Nano ESP32 requires:

• PWM plus filtering;
• an external DAC;
• an I²S DAC/codec.

PWM

Nano ESP32 has flexible LEDC-based PWM that can be assigned to many suitable GPIO.

Nano 33 IoT uses SAMD21 TCC/TC timer hardware and provides PWM on several fixed/default Arduino pins.

For ordinary analogWrite(), both are easy to use.

For advanced timer work, the ESP32-S3 architecture is generally more flexible.

Nano 33 IoT Has a Dedicated Secure Element

The board includes:

for protected key storage and device identity.

This was central to Nano 33 IoT’s Arduino Cloud design.

Nano ESP32 does not use a separate ATECC608A on the board, but ESP32-S3 includes hardware security features such as:

• secure boot;
• Flash encryption;
• cryptographic acceleration;
• eFuse-backed security configuration.

Onboard IMU

Nano 33 IoT includes an onboard 6-axis IMU.

Arduino’s current April 2026 datasheet lists:

while some older product documentation still references the earlier LSM6DS3 wording.

The exact sensor revision therefore depends on current board documentation and production revision.

Nano ESP32 does not include an onboard IMU.

If Motion Sensing Matters

Nano 33 IoT has the convenience advantage because no external IMU is required.

Nano ESP32 has more processing power for sensor fusion or ML, but you need to add the sensor yourself.

Arduino Cloud

Both boards support Arduino Cloud.

Nano 33 IoT was designed around:

• WiFiNINA;
• ATECC608A security;
• Arduino Cloud connectivity.

Nano ESP32 achieves the same broad goal through its native ESP32 networking environment.

Power Consumption

Nano 33 IoT can be attractive for modest IoT workloads because the SAMD21 application MCU is relatively small and the NINA radio can be controlled separately.

Nano ESP32 also supports deep sleep and advanced ESP32 power management, but its larger architecture means actual board consumption depends heavily on:

• Wi-Fi duty cycle;
• BLE use;
• PSRAM use;
• CPU frequency;
• peripheral activity.

For battery design, measure the complete board in the actual duty cycle rather than comparing only chip-level sleep-current numbers.

Software Ecosystem

Nano ESP32

You gain access to:

• Arduino-ESP32;
• ESP-IDF concepts;
• ESP-NOW;
• ESP32 BLE libraries;
• MicroPython;
• huge ESP32 community support.

Nano 33 IoT

You gain access to:

• Arduino SAMD ecosystem;
• WiFiNINA;
• ArduinoBLE;
• SAMD21 native USB libraries;
• Crypto/ATECC608A libraries;
• mature Arduino Cloud examples.

Library Compatibility

A library written for high-level Arduino APIs may support both.

But architecture-specific libraries differ significantly.

Code containing:

will not port directly to ESP32-S3.

Likewise, code using:

will not run on SAMD21.

Which Board Is Better for MQTT?

For a new MQTT project, Nano ESP32 generally has the stronger architecture because it offers:

• far more RAM;
• larger TLS buffers;
• more CPU headroom;
• native networking;
• larger certificates/filesystems.

Nano 33 IoT can still run MQTT effectively, but memory is much tighter.

Which Board Is Better for a Web Server?

Nano ESP32.

The combination of:

makes it much better suited to:

• HTML/CSS assets;
• JSON APIs;
• multiple clients;
• larger response buffers.

Which Board Is Better for USB HID?

Both can do native USB.

Nano 33 IoT’s SAMD21 has a long history of USB HID use in Arduino projects.

Nano ESP32’s ESP32-S3 is also very capable and adds USB/JTAG debugging.

For a new high-performance USB + wireless project, Nano ESP32 usually gives more headroom.

Which Board Is Better for Analog Output?

Nano 33 IoT wins because of:

Nano ESP32 has no true DAC.

Which Board Is Better for Existing SAMD21 Code?

Nano 33 IoT wins immediately.

If the project already uses:

• SAMD21 registers;
• SERCOM tricks;
• SAMD-specific timers;
• Arduino SAMD libraries;

there may be little benefit in migrating solely for the sake of newer hardware.

Which Board Is Better for New IoT Projects?

For most new Wi-Fi-heavy projects, Nano ESP32 is the stronger default because it provides:

• much more memory;
• much more CPU performance;
• native radio integration;
• MicroPython;
• ESP-NOW;
• USB-C;
• larger Flash.

Nano 33 IoT remains attractive when its specific features matter:

• SAMD21 compatibility;
• ATECC608A;
• true DAC;
• onboard IMU;
• existing WiFiNINA software.

Migration from Nano 33 IoT to Nano ESP32

High-level code using:

is relatively easy to port.

Review carefully:

• WiFiNINA-specific APIs;
• ArduinoBLE behaviour;
• SAMD timer/register code;
• A0 DAC use;
• IMU code;
• pin numbering;
• USB library behaviour.

Nano ESP32 Pin Numbering Requires Extra Attention

Nano ESP32 has two numbering concepts:

For example:

Use symbolic names such as:

rather than assuming Arduino pin 2 means GPIO2.

Nano 33 IoT does not have this same numbering trap.

Quick Decision Table

Requirement	Better fit
Highest CPU performance	Nano ESP32
Most RAM	Nano ESP32
Wi-Fi web server	Nano ESP32
MQTT with large TLS buffers	Nano ESP32
ESP-NOW	Nano ESP32
MicroPython	Nano ESP32
USB-C	Nano ESP32
True DAC	Nano 33 IoT
Onboard IMU	Nano 33 IoT
ATECC608A secure element	Nano 33 IoT
Existing SAMD21 code	Nano 33 IoT
Existing WiFiNINA project	Nano 33 IoT

Quick Reference

Final Thoughts

Nano ESP32 is not simply a faster Nano 33 IoT.

It replaces the older split:

with a much more integrated:

architecture.

For new Wi-Fi-heavy IoT projects, Nano ESP32 is usually the stronger platform because of its CPU speed, 8 MB PSRAM, 16 MB Flash, native wireless stack and ESP32 ecosystem.

Nano 33 IoT still has several reasons to exist in an established project:

• the A0 true DAC;
• onboard IMU;
• ATECC608A secure element;
• SAMD21 compatibility;
• existing WiFiNINA code.

The simplest decision rule is:

For full pin mappings, see our Nano ESP32 pinout guide and Nano 33 IoT pinout guide.