Arduino Portenta C33 Pinout: GPIO, ADC, DAC, PWM, CAN, UART, SPI, I2C, USB and Ethernet

The Arduino Portenta C33 is a cost-optimised industrial IoT module built around the Renesas RA6M5 microcontroller.

Its architecture combines:

The board uses the same Portenta family form factor as the H7, so it keeps the familiar MKR-style edge headers while exposing most industrial interfaces through the two high-density connectors underneath.

Quick Portenta C33 Specifications

Feature	Portenta C33
Main MCU	Renesas R7FA6M5BH2CBG / RA6M5
CPU	Arm Cortex-M33
Clock	Up to 200 MHz
Internal Flash	2 MB
SRAM	512 KB
External Flash	16 MB QSPI
Logic voltage	3.3 V
Main digital pins	D0-D14
Main analogue pins	A0-A6
Additional analogue input	A7 on high-density connector
DAC	2 external DAC-capable pins: A5 and A6
PWM	Main-header D0-D6 plus additional high-density PWM
UART	Multiple SCI/UART channels through header and HDC
I2C	Multiple I2C buses
SPI	Main SPI plus SPI0/SPI1 on HDC
CAN	CAN0 and CAN1 TX/RX pairs on HDC
Ethernet	100Mb Ethernet PHY
USB	USB-C High Speed plus USB0/USB1 signals on HDC
Wireless	ESP32-C3-MINI-1U Wi-Fi + BLE
Secure element	NXP SE050C2
Operating temperature	-40 °C to +85 °C
Dimensions	66.04 × 25.40 mm

3.3 V Logic

The Portenta C33 is a:

Do not confuse the presence of:

power pins with 5 V-compatible GPIO.

Check signal voltage before connecting:

• 5 V sensors;
• legacy Arduino shields;
• UART modules;
• I2C devices with 5 V pull-ups;
• SPI peripherals.

GPIO Current Limits

Arduino’s current full pinout specifies:

Those are board limits, not recommended operating targets.

Use external drivers for:

• relays;
• motors;
• solenoids;
• large LEDs;
• high-current loads.

Main MKR-Style Digital Pin Mapping

The standard top headers expose:

with the following primary RA6M5 mappings:

Arduino pin	RA6M5 pin	Main function
D0	P105	GPIO / PWM
D1	P106	GPIO / PWM
D2	P111	GPIO / PWM
D3	P303	GPIO / PWM
D4	P401	GPIO / PWM
D5	P210	GPIO / PWM
D6	P601	GPIO / PWM
D7	P402	SPI CS / SCI_CTS4
D8	P900	SPI COPI / SCI_TXD4
D9	P204	SPI SCK / SCI_SCK4
D10	P315	SPI CIPO / SCI_RXD4
D11	P407	I2C SDA
D12	P408	I2C SCL
D13	P110	UART RX / SCI_RXD9
D14	P602	UART TX / SCI_TXD9

PWM on the Main Header

The current Arduino pinout marks:

as PWM-capable on the standard MKR-style header.

The high-density connectors expose additional PWM timer outputs labelled:

for carrier-board applications.

Analogue Inputs

The main header exposes:

and the high-density connector adds:

as another ADC-capable input.

Arduino pin	RA6M5 pin	ADC/DAC function
A0	P006	AN006
A1	P005	AN005
A2	P004	AN004
A3	P002	AN002
A4	P001	AN001
A5	P015	AN013 / DAC1
A6	P014	AN012 / DAC0
A7	HDC only	ADC A7

Two True DAC Outputs

One useful difference from Portenta H7’s normal user-facing pinout is that Portenta C33 exposes two DAC-capable analogue pins:

These are genuine analogue outputs rather than PWM.

This is useful for:

• control voltages;
• waveform generation;
• analogue setpoints;
• audio experiments;
• industrial reference signals.

ADC Reference Pins

The high-density connector exposes:

for advanced analogue configurations.

This is especially useful in carrier designs where ADC accuracy and reference stability matter.

SPI on the Main Header

The default SPI mapping is:

Use:

SPI Example

Two Additional SPI Groups on the HDC

The J2 high-density connector exposes:

This is useful for custom carrier boards that need multiple independent SPI buses.

As always, the physical hardware labels and Arduino software object names may not map one-to-one, so check the current core API when using non-default buses.

I2C on the Main Header

The normal external I2C bus uses:

Use:

Additional I2C Buses

The high-density connectors also expose:

giving the board considerably more flexibility than the normal MKR header suggests.

UART on the Main Header

The default external serial pair is:

This is the normal hardware serial connection for many Arduino sketches.

Additional UARTs

The high-density connectors expose multiple SCI/UART groups:

with RTS/CTS hardware-flow-control signals on several groups.

This is valuable for:

• industrial modems;
• GNSS receivers;
• serial instruments;
• RS-485 transceiver interfaces;
• multiple MCU links.

Dual CAN Interfaces

The Portenta C33 high-density connector exposes two separate CAN controller signal pairs:

This is a significant industrial feature.

CAN Still Requires External Transceivers

The pins are logic-level:

not:

Each physical CAN bus requires a suitable transceiver.

If using two independent CAN networks, each CAN controller needs its own physical transceiver path.

Ethernet

Portenta C33 includes a:

and exposes the differential Ethernet pairs on J1:

along with LED/status signals:

No RJ45 on the Module

As with Portenta H7, the SoM itself does not contain a conventional RJ45 socket.

A carrier board provides:

• RJ45 connector;
• magnetics;
• mechanical interface;
• supporting protection/components.

USB-C High Speed

The Portenta C33 uses:

for programming, power and native USB communication.

Arduino lists:

in the current product specification.

Additional USB Interfaces on HDC

The high-density connector exposes:

for carrier-board USB connectivity.

SD Card Interface

The J1 connector exposes a native SD interface:

This allows a Portenta carrier to provide a high-performance SD-card socket without using the main SPI bus.

I2S Digital Audio

Portenta C33 exposes an I2S group on the high-density connector:

for:

• audio codecs;
• digital microphones;
• digital amplifiers;
• streaming audio.

Additional GPIO on the High-Density Connector

J2 provides general-purpose signals labelled:

in addition to the standard D0-D14 pins.

This is why the Portenta form factor can support much larger custom carrier designs than an ordinary MKR board.

Debug Interface

The J1 connector exposes:

for low-level debugging and production programming.

Single-Core Cortex-M33 Architecture

Unlike Portenta H7, the C33 is not a dual-core board.

It uses one:

application processor.

This makes the architecture simpler than:

but it also means there is no second real-time Cortex core to partition application tasks onto.

TrustZone

The Cortex-M33 supports:

which allows software to create:

execution regions.

This can be useful for industrial devices where:

• keys;
• boot validation;
• secure services;
• application code;

need different security boundaries.

Secure Crypto Engine 9

The RA6M5 also includes:

for hardware-accelerated cryptographic operations.

This complements the separate onboard:

secure element.

SE050C2 Secure Element

The secure element is intended for:

• device identity;
• private-key storage;
• certificate operations;
• secure authentication;
• industrial IoT security.

ESP32-C3 Wireless Co-Processor

The board uses:

for wireless connectivity.

It provides:

while the RA6M5 remains the main application MCU.

Wireless Architecture

The normal software model is:

This is conceptually similar to other Arduino boards that use a separate radio processor.

External Antenna

The ESP32-C3-MINI-1U is the U.FL-style module variant intended for use with an external antenna.

Use an antenna appropriate for:

and the intended mechanical enclosure.

16 MB External QSPI Flash

In addition to the RA6M5’s:

the board includes:

for larger:

• filesystems;
• OTA images;
• assets;
• data storage;
• application resources.

512 KB SRAM

The C33 has:

which is far larger than classic Arduino-class MCUs, but smaller than the H7 platform once its external SDRAM is considered.

MicroPython Support

Arduino officially supports:

and other high-level language workflows on Portenta C33.

The:

make it substantially more comfortable for high-level scripting than small AVR or SAMD boards.

Li-Po Battery Support

The board includes support for a:

through its battery connector and PMIC.

The current full pinout contains an important warning:

because the charger expects battery-temperature monitoring.

+3V3_EXT Is Not the MCU 3.3 V Rail

This is a particularly important Portenta C33 power detail.

The pinout explicitly states:

Instead:

Do not assume every 3.3 V label on the board refers to the same power domain.

VIN and 5 V

The main headers expose:

Power design should follow the official Portenta C33 datasheet rather than UNO-style assumptions.

Portenta H7 Compatibility

Arduino describes Portenta C33 as backward-compatible with the Portenta H7 form factor.

It is compatible with the Portenta carrier/shield ecosystem through the:

However, physical connector compatibility does not mean every H7-specific software feature is automatically available.

What C33 Does Not Have from H7

Portenta C33 is a streamlined board.

Compared with H7 it does not provide the same:

• dual-core M7/M4 architecture;
• 480 MHz M7 performance;
• 8 MB SDRAM;
• MIPI DSI display interface;
• camera DCMI-oriented feature set;
• DisplayPort-over-USB-C workflow.

Its focus is instead:

Common Mistake 1: Applying 5 V to GPIO

The C33 is a:

Use proper voltage translation where necessary.

Common Mistake 2: Assuming H7 and C33 Are Electrically Identical

The carrier form factor is compatible, but:

Peripheral capabilities, pin functions, memory and software architecture differ.

Common Mistake 3: Connecting CANH/CANL Directly

CAN0 and CAN1 pins are logic-level TX/RX signals.

Use a proper CAN transceiver for each physical network.

Common Mistake 4: Ignoring the 8 mA GPIO Limit

Portenta C33 has lower pin-current limits than many users expect from older Arduino boards.

Use external load drivers.

Common Mistake 5: Assuming +3V3_EXT Is the MCU Supply Rail

It is a separate PMIC-generated rail.

Read the carrier power requirements before tying rails together.

Common Mistake 6: Using a Two-Wire Li-Po Without Temperature Sense

The official pinout warns that the battery:

for the onboard charging system.

Common Mistake 7: Assuming Every HDC Bus Has a Ready-Made Arduino Object

The physical connectors expose many RA6M5 peripheral signals.

Some advanced functions may require:

• custom Renesas FSP configuration;
• lower-level core APIs;
• carrier-specific libraries.

Quick Main-Header Reference

Quick Analogue Reference

Quick High-Density Reference

Final Thoughts

The Arduino Portenta C33 is best understood as:

The normal MKR-style header provides familiar Arduino wiring:

while the two 80-pin connectors add:

Compared with Portenta H7, C33 gives up the dual-core STM32H747, large SDRAM and high-end multimedia interfaces in exchange for a simpler, lower-cost architecture centred on:

For the higher-performance dual-core alternative, see our Arduino Portenta H7 pinout guide. For a maker-oriented STM32H747 board, see our Arduino GIGA R1 WiFi pinout guide.