Arduino MKR WiFi 1010 Pinout: GPIO, ADC, DAC, PWM, UART, SPI and I2C

The Arduino MKR WiFi 1010 is a compact IoT board built around the SAMD21 Cortex-M0+ processor and a separate u-blox NINA-W102 wireless module.

Its main architecture is:


SAMD21
→ 48 MHz Cortex-M0+
→ runs your Arduino sketch
→ handles GPIO, ADC, DAC, timers, USB and serial buses

NINA-W102
→ 2.4 GHz Wi-Fi
→ Bluetooth / BLE
→ wireless co-processor

SAMD21

→ 48 MHz Cortex-M0+

→ runs your Arduino sketch

→ handles GPIO, ADC, DAC, timers, USB and serial buses

NINA-W102

→ 2.4 GHz Wi-Fi

→ Bluetooth / BLE

→ wireless co-processor

The board also includes:

3.3 V logic;
native USB;
single-cell Li-Po charging;
ATECC508 secure element;
7 external analogue inputs;
one true 10-bit DAC output;
13 PWM-capable header pins;
UART, SPI and I2C;
an additional Eslov I2C connector.

Quick MKR WiFi 1010 Specifications

Feature	MKR WiFi 1010
Main MCU	SAMD21 Cortex-M0+
Clock	48 MHz
Logic voltage	3.3 V
Flash	256 KB
SRAM	32 KB
EEPROM	No dedicated EEPROM
Digital-labelled header pins	D0-D14
Analog inputs	A0-A6
ADC resolution	8/10/12-bit selectable
DAC	A0, 10-bit
PWM-capable header pins	13
UART	1 external hardware UART
SPI	1 external SPI bus
I2C	1 external I2C bus
Wi-Fi	2.4 GHz 802.11 b/g/n via NINA-W102
Bluetooth	Bluetooth / BLE via NINA-W102
USB	Full-Speed USB device and embedded host capability
Secure element	ATECC508
Battery	Single-cell 3.7 V Li-Po
GPIO current	7 mA maximum per pin
Size	61.5 × 25 mm

Important: MKR WiFi 1010 Uses 3.3 V Logic

The most important electrical rule is:


GPIO HIGH ≈ 3.3 V

GPIO HIGH ≈ 3.3 V

The SAMD21 is not a 5 V AVR device.

Do not assume a sensor, shield or module designed for UNO/Mega 5 V logic can be connected directly.

Before connecting a 5 V peripheral, check:

its input HIGH threshold;
its output voltage;
I2C pull-up voltage;
SPI/UART signal voltage;
whether level shifting is required.

GPIO Current Limit

The official MKR WiFi 1010 pinout gives a maximum of:


7 mA per I/O pin

7 mA per I/O pin

with group-level source/sink limits as well.

This is much lower than the current figures users may remember from older AVR boards.

Do not directly drive:

relays;
motors;
solenoids;
high-power LEDs;
large buzzers.

Use a transistor, MOSFET or dedicated driver.

Digital Pin Mapping

The board edge exposes digital labels:


D0-D14

D0-D14

with the following main SAMD21 mappings:

Arduino pin	SAMD21 pin	Main alternate functions
D0	PA22	PWM
D1	PA23	PWM
D2	PA10	PWM
D3	PA11	PWM
D4	PB10	PWM
D5	PB11	PWM
D6	PA20	PWM / LED_BUILTIN
D7	PA21	PWM
D8	PA16	PWM / SPI COPI
D9	PA17	SPI SCK
D10	PA19	PWM / SPI CIPO
D11	PA08	I2C SDA
D12	PA09	PWM / I2C SCL
D13	PB23	UART RX
D14	PB22	UART TX

Why Arduino’s Store Says “8 Digital I/O Pins”

The current Arduino store specification lists:


Digital I/O Pins: 8

Digital I/O Pins: 8

but the physical pinout clearly labels:


D0-D14

D0-D14

because several communication and analogue-capable pins can also be used as normal digital GPIO.

For practical wiring, the full pinout map is more useful than treating the headline “8” as the total number of usable digital-labelled pins.

LED_BUILTIN

The onboard user LED is:


D6
→ PA20

→ PA20

so the normal Blink sketch works with:


LED_BUILTIN

LED_BUILTIN

PWM Pins

The official pinout marks 13 PWM-capable header positions:


D0
D1
D2
D3
D4
D5
D6
D7
D8
D10
D12
A3 / D18
A4 / D19

D10

D12

A3 / D18

A4 / D19

Notice that:


D9
D11
D13
D14

D11

D13

D14

are not marked as default PWM outputs in the board pinout.

PWM Example


void setup() {
  pinMode(6, OUTPUT);
}

void loop() {
  analogWrite(6, 128);
}

void setup() {

pinMode(6, OUTPUT);

}

void loop() {

analogWrite(6, 128);

}

On most pins this generates PWM.

A0 is different because it can provide a true DAC output.

Analog Inputs A0-A6

The MKR WiFi 1010 exposes seven analogue inputs:


A0
A1
A2
A3
A4
A5
A6

Analog pin	Digital alias	SAMD21 pin	ADC channel
A0	D15	PA02	AIN0 / DAC0
A1	D16	PB02	AIN10
A2	D17	PB03	AIN11
A3	D18	PA04	AIN4
A4	D19	PA05	AIN5
A5	D20	PA06	AIN6
A6	D21	PA07	AIN7

Analog Pins Can Also Be Digital GPIO

The analogue pins have digital aliases:


A0 = D15
A1 = D16
A2 = D17
A3 = D18
A4 = D19
A5 = D20
A6 = D21

A0 = D15

A1 = D16

A2 = D17

A3 = D18

A4 = D19

A5 = D20

A6 = D21

So a pin such as A5 can also be used with:


pinMode(A5, OUTPUT);
digitalWrite(A5, HIGH);

pinMode(A5, OUTPUT);

digitalWrite(A5, HIGH);

ADC Resolution

The official specification lists ADC operation at:


8-bit
10-bit
12-bit

8-bit

10-bit

12-bit

The SAMD core supports changing read resolution with:


analogReadResolution(12);

analogReadResolution(12);

For example:


void setup() {
  Serial.begin(115200);

  analogReadResolution(12);
}

void loop() {
  int value = analogRead(A1);

  Serial.println(value);
  delay(100);
}

void setup() {

Serial.begin(115200);

analogReadResolution(12);

}

void loop() {

int value = analogRead(A1);

Serial.println(value);

delay(100);

}

At 12-bit resolution, the normal range is:


0-4095

0-4095

A0 Is a True DAC Output

A0 is special:


A0 / D15
→ PA02
→ DAC0

A0 / D15

→ PA02

→ DAC0

The official board specification describes the analogue output as:


10-bit DAC

10-bit DAC

This is a genuine analogue output, not just PWM.

DAC Example


void setup() {
  analogWriteResolution(10);
}

void loop() {
  analogWrite(A0, 512);
}

void setup() {

analogWriteResolution(10);

}

void loop() {

analogWrite(A0, 512);

}

This targets approximately mid-scale output.

Do Not Treat A0 Like an UNO PWM Pin

On the MKR WiFi 1010:


A0
→ true DAC-capable output

→ true DAC-capable output

whereas on many classic Arduino boards:


analogWrite()
→ PWM only

analogWrite()

→ PWM only

AREF

The board exposes:


AREF
→ PA03

AREF

→ PA03

for analogue-reference use.

Follow the SAMD21 and Arduino reference-voltage rules when applying an external AREF.

Hardware UART

The external hardware UART is:


D13
→ RX
→ PB23

D14
→ TX
→ PB22

D13

→ RX

→ PB23

D14

→ TX

→ PB22

Use:


Serial1

Serial1

for those pins.

USB Serial vs Serial1

Because the SAMD21 has native USB:


Serial
→ USB CDC serial

Serial1
→ D13/D14 hardware UART

Serial

→ USB CDC serial

Serial1

→ D13/D14 hardware UART

This allows the board to communicate with a PC over USB while simultaneously talking to a GPS, modem or another MCU over the hardware UART.

UART Example


void setup() {
  Serial.begin(115200);
  Serial1.begin(9600);
}

void loop() {
  while (Serial1.available()) {
    Serial.write(
      Serial1.read()
    );
  }
}

void setup() {

Serial.begin(115200);

Serial1.begin(9600);

}

void loop() {

while (Serial1.available()) {

Serial.write(

Serial1.read()

);

}

I2C Pins

The main I2C bus is:


D11
→ SDA
→ PA08

D12
→ SCL
→ PA09

D11

→ SDA

→ PA08

D12

→ SCL

→ PA09

Use:


#include &lt;Wire.h&gt;

#include <Wire.h>

I2C Example


#include &lt;Wire.h&gt;

void setup() {
  Wire.begin();
}

void loop() {
}

#include <Wire.h>

void setup() {

Wire.begin();

}

void loop() {

}

Additional Eslov I2C Connector

The MKR WiFi 1010 also includes a small 5-pin:


Eslov

Eslov

connector carrying:

SDA;
SCL;
GND;
+5 V;
WK / wake-alarm signal.

The SDA/SCL signals are the same I2C bus rather than a completely independent second I2C controller.

Be Careful with the Eslov 5 V Pin

The connector includes:


+5 V

+5 V

power, but the SAMD21 communication signals remain:


3.3 V logic

3.3 V logic

Do not assume the presence of 5 V power means the I2C pins are 5 V logic.

SPI Pins

The main external SPI mapping is:


D8
→ COPI / MOSI
→ PA16

D9
→ SCK
→ PA17

D10
→ CIPO / MISO
→ PA19

→ COPI / MOSI

→ PA16

→ SCK

→ PA17

D10

→ CIPO / MISO

→ PA19

Use:


#include &lt;SPI.h&gt;

#include <SPI.h>

SPI Example


#include &lt;SPI.h&gt;

const int csPin = 4;

void setup() {
  pinMode(csPin, OUTPUT);
  digitalWrite(csPin, HIGH);

  SPI.begin();
}

void loop() {
}

#include <SPI.h>

const int csPin = 4;

void setup() {

pinMode(csPin, OUTPUT);

digitalWrite(csPin, HIGH);

SPI.begin();

}

void loop() {

}

Chip select can generally be assigned to a suitable free GPIO unless a library or peripheral requires a specific pin.

Native USB

The SAMD21 provides native:


Full-Speed USB

Full-Speed USB

and the board supports USB device operation as well as embedded-host capability.

This enables projects such as:

USB serial devices;
keyboard/mouse HID;
custom USB peripherals.

Micro-USB Connector

The MKR WiFi 1010 uses a:


Micro-USB

Micro-USB

connector for normal:

programming;
power;
USB data.

Wi-Fi Hardware

Wireless networking is handled by the:


u-blox NINA-W102

u-blox NINA-W102

module.

Its wireless hardware supports:


2.4 GHz
802.11b
802.11g
802.11n

2.4 GHz

802.11b

802.11g

802.11n

with up to 72 Mbit/s PHY rate for 802.11n according to Arduino’s current datasheet.

The NINA-W102 Contains Its Own Processor

The wireless module contains a:


dual-core Tensilica LX6
up to 240 MHz

dual-core Tensilica LX6

up to 240 MHz

processor.

However, in normal MKR WiFi 1010 use:


SAMD21
→ runs your Arduino sketch

NINA-W102
→ operates as wireless co-processor

SAMD21

→ runs your Arduino sketch

NINA-W102

→ operates as wireless co-processor

You do not normally write the main Arduino application to the NINA module.

WiFiNINA Library

The standard Wi-Fi software path is:


#include &lt;WiFiNINA.h&gt;

#include <WiFiNINA.h>

For example:


#include &lt;WiFiNINA.h&gt;

char ssid[] = "YOUR_WIFI";
char pass[] = "YOUR_PASSWORD";

void setup() {
  Serial.begin(115200);

  WiFi.begin(ssid, pass);
}

void loop() {
}

#include <WiFiNINA.h>

char ssid[] = "YOUR_WIFI";

char pass[] = "YOUR_PASSWORD";

void setup() {

Serial.begin(115200);

WiFi.begin(ssid, pass);

}

void loop() {

}

Bluetooth and BLE

Arduino’s current NINA-W102 datasheet lists:

Bluetooth BR/EDR;
Bluetooth Low Energy;
Bluetooth 5.0 dual-mode radio capability.

Arduino projects normally use the supported Arduino Bluetooth libraries and firmware interfaces rather than programming the radio stack directly.

ATECC508 Secure Element

The board includes a:


Microchip ATECC508

Microchip ATECC508

secure element.

This is useful for:

secure key storage;
device identity;
TLS authentication;
Arduino Cloud provisioning.

Li-Po Battery Connector

The MKR family was designed for portable IoT applications.

The MKR WiFi 1010 therefore includes a connector for a:


3.7 V single-cell Li-Po

3.7 V single-cell Li-Po

and onboard charging circuitry.

Arduino’s current store specification recommends a battery of at least:


1024 mAh

1024 mAh

Battery Charging

When USB power is connected, the onboard charger can recharge the attached Li-Po battery.

This makes the board suitable for:

portable sensors;
remote data loggers;
battery-backed IoT nodes;
mobile BLE devices.

VIN Is Not the Same as UNO VIN

This is an important MKR difference.

Arduino documents VIN as a regulated input in approximately the:


5-6 V

5-6 V

range.

Do not connect:


9 V
12 V

9 V

12 V

to MKR VIN just because a classic UNO or Mega can accept those voltages.

5 V Pin

The board exposes:

+5V

+5V

which is derived from USB/VIN under normal powered operation.

Again:


5 V power rail
≠
5 V GPIO

5 V power rail

≠

5 V GPIO

3.3 V Pin

The:


+3V3

+3V3

pin provides the board’s regulated 3.3 V supply.

This is the natural power rail for most external logic connected directly to SAMD21 GPIO.

RTC Clock

The SAMD21 includes an RTC subsystem and the board specification lists:


32.768 kHz RTC

32.768 kHz RTC

alongside the:


48 MHz CPU clock

48 MHz CPU clock

No Dedicated EEPROM

The MKR WiFi 1010 does not include classic AVR-style onboard EEPROM in the main SAMD21 specification.

If your application needs persistent settings, use an appropriate Flash-emulation or external-storage approach.

External Interrupts

Arduino’s current store specification lists external interrupts on:


D0
D1
D4
D5
D6
D7
D8
D9
A1 / D16
A2 / D17

A1 / D16

A2 / D17

for a total of:


10 documented external-interrupt pins

10 documented external-interrupt pins

External Interrupt Example


volatile bool triggered = false;

void onInput() {
  triggered = true;
}

void setup() {
  pinMode(4, INPUT_PULLUP);

  attachInterrupt(
    digitalPinToInterrupt(4),
    onInput,
    FALLING
  );
}

void loop() {
  if (triggered) {
    triggered = false;
  }
}

volatile bool triggered = false;

void onInput() {

triggered = true;

}

void setup() {

pinMode(4, INPUT_PULLUP);

attachInterrupt(

digitalPinToInterrupt(4),

onInput,

FALLING

);

}

void loop() {

if (triggered) {

triggered = false;

}

SWD Debug Pins

The bottom of the board exposes SWD programming/debug signals including:


SWDIO
SWCLK
GND
3.3 V

SWDIO

SWCLK

GND

3.3 V

These allow advanced debugging and low-level programming of the SAMD21 with suitable tools.

Pin Conflicts with the Wireless Module

Several internal SAMD21 pins are reserved for communication with the NINA-W102.

The SAMD21 and NINA communicate through internal:

SPI;
UART/control signals;
reset/acknowledge lines.

Those internal connections are separate from the normal user-facing SPI/UART pins, but they consume SAMD21 SERCOM/peripheral resources.

Common Mistake 1: Applying 5 V to GPIO

The board is a:


3.3 V logic platform

3.3 V logic platform

Do not assume 5 V tolerance.

Common Mistake 2: Feeding 9-12 V into VIN

MKR VIN is not a classic UNO VIN input.

Use the documented:


5-6 V regulated input range

5-6 V regulated input range

or USB/battery power.

Common Mistake 3: Assuming A0 Is Only an ADC

A0 is also:


DAC0

DAC0

and can generate a genuine analogue output.

Common Mistake 4: Assuming D9 Is PWM

The official pinout does not mark:

D9

as a default PWM pin, even though it is the SPI clock.

Common Mistake 5: Confusing Serial and Serial1

Use:


Serial
→ USB

Serial1
→ D13/D14 UART

Serial

→ USB

Serial1

→ D13/D14 UART

Common Mistake 6: Powering a Heavy Load from GPIO

The official pinout gives:


7 mA maximum per pin

7 mA maximum per pin

so external load drivers are important.

Quick Digital Reference


D0  PA22 PWM
D1  PA23 PWM
D2  PA10 PWM
D3  PA11 PWM
D4  PB10 PWM
D5  PB11 PWM
D6  PA20 PWM / LED
D7  PA21 PWM
D8  PA16 PWM / COPI
D9  PA17 SCK
D10 PA19 PWM / CIPO
D11 PA08 SDA
D12 PA09 PWM / SCL
D13 PB23 RX
D14 PB22 TX

D0 PA22 PWM

D1 PA23 PWM

D2 PA10 PWM

D3 PA11 PWM

D4 PB10 PWM

D5 PB11 PWM

D6 PA20 PWM / LED

D7 PA21 PWM

D8 PA16 PWM / COPI

D9 PA17 SCK

D10 PA19 PWM / CIPO

D11 PA08 SDA

D12 PA09 PWM / SCL

D13 PB23 RX

D14 PB22 TX

Quick Analog Reference


A0 / D15
PA02
AIN0
DAC0

A1 / D16
PB02
AIN10

A2 / D17
PB03
AIN11

A3 / D18
PA04
AIN4
PWM

A4 / D19
PA05
AIN5
PWM

A5 / D20
PA06
AIN6

A6 / D21
PA07
AIN7

A0 / D15

PA02

AIN0

DAC0

A1 / D16

PB02

AIN10

A2 / D17

PB03

AIN11

A3 / D18

PA04

AIN4

PWM

A4 / D19

PA05

AIN5

PWM

A5 / D20

PA06

AIN6

A6 / D21

PA07

AIN7

Quick Communications Reference


USB serial:
Serial

Hardware UART:
D13 RX
D14 TX
Serial1

I2C:
D11 SDA
D12 SCL

SPI:
D8  COPI / MOSI
D9  SCK
D10 CIPO / MISO

Wireless:
NINA-W102
2.4 GHz Wi-Fi
Bluetooth / BLE

USB serial:

Serial

Hardware UART:

D13 RX

D14 TX

Serial1

I2C:

D11 SDA

D12 SCL

SPI:

D8 COPI / MOSI

D9 SCK

D10 CIPO / MISO

Wireless:

NINA-W102

2.4 GHz Wi-Fi

Bluetooth / BLE

Final Thoughts

The Arduino MKR WiFi 1010 remains a useful compact IoT board because it combines:


SAMD21
48 MHz Cortex-M0+
256 KB Flash
32 KB SRAM
native USB
true DAC
Wi-Fi
Bluetooth
secure element
Li-Po charging

SAMD21

48 MHz Cortex-M0+

256 KB Flash

32 KB SRAM

native USB

true DAC

Wi-Fi

Bluetooth

secure element

Li-Po charging

in a narrow MKR form factor.

The most important pinout rules are:


logic voltage
→ 3.3 V

UART
→ D13 RX / D14 TX

I2C
→ D11 SDA / D12 SCL

SPI
→ D8 COPI / D9 SCK / D10 CIPO

analog
→ A0-A6

DAC
→ A0

LED_BUILTIN
→ D6

maximum GPIO current
→ 7 mA per pin

logic voltage

→ 3.3 V

UART

→ D13 RX / D14 TX

I2C

→ D11 SDA / D12 SCL

SPI

→ D8 COPI / D9 SCK / D10 CIPO

analog

→ A0-A6

DAC

→ A0

LED_BUILTIN

→ D6

maximum GPIO current

→ 7 mA per pin

The two biggest electrical traps are applying 5 V to the GPIO and treating MKR VIN like an UNO’s wide-range VIN input.

For IoT applications, the combination of the SAMD21, NINA-W102 radio, secure element and onboard Li-Po charging is what makes the MKR WiFi 1010 distinct from a simple Wi-Fi development board.

Quick MKR WiFi 1010 Specifications

Important: MKR WiFi 1010 Uses 3.3 V Logic

GPIO Current Limit

Digital Pin Mapping

Why Arduino’s Store Says “8 Digital I/O Pins”

LED_BUILTIN

PWM Pins

PWM Example

Analog Inputs A0-A6

Analog Pins Can Also Be Digital GPIO

ADC Resolution

A0 Is a True DAC Output

DAC Example

Do Not Treat A0 Like an UNO PWM Pin

AREF

Hardware UART

USB Serial vs Serial1

UART Example

I2C Pins

I2C Example

Additional Eslov I2C Connector

Be Careful with the Eslov 5 V Pin

SPI Pins

SPI Example

Native USB

Micro-USB Connector

Wi-Fi Hardware

The NINA-W102 Contains Its Own Processor

WiFiNINA Library

Bluetooth and BLE

ATECC508 Secure Element

Li-Po Battery Connector

Battery Charging

VIN Is Not the Same as UNO VIN

5 V Pin

3.3 V Pin

RTC Clock

No Dedicated EEPROM

External Interrupts

External Interrupt Example

SWD Debug Pins

Pin Conflicts with the Wireless Module

Common Mistake 1: Applying 5 V to GPIO

Common Mistake 2: Feeding 9-12 V into VIN

Common Mistake 3: Assuming A0 Is Only an ADC

Common Mistake 4: Assuming D9 Is PWM

Common Mistake 5: Confusing Serial and Serial1

Common Mistake 6: Powering a Heavy Load from GPIO

Quick Digital Reference

Quick Analog Reference

Quick Communications Reference

Final Thoughts

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