Arduino MKR NB 1500 Pinout: GPIO, ADC, DAC, PWM, UART, SPI, I2C and LTE-M/NB-IoT

The Arduino MKR NB 1500 is a compact cellular IoT board built around the SAMD21 Cortex-M0+ microcontroller and a u-blox SARA-R410M-02B LTE modem.

Its architecture is:

The board is designed for remote sensors, telemetry, metering and other applications where Wi-Fi is not available but low-power cellular coverage is.

Quick MKR NB 1500 Specifications

Feature	MKR NB 1500
Main MCU	SAMD21 Cortex-M0+
Clock	48 MHz
RTC clock	32.768 kHz
Logic voltage	3.3 V
Flash	256 KB
SRAM	32 KB
EEPROM	No dedicated EEPROM
Analog inputs	7, A0-A6
ADC	8/10/12-bit selectable
DAC	1 × 10-bit on A0
PWM	13 documented PWM-capable pins
UART	1 external hardware UART
SPI	1 external SPI bus
I2C	1 external I2C bus
Cellular modem	u-blox SARA-R410M-02B
Cellular technologies	LTE Cat M1 / NB-IoT
Secure element	ATECC508
Battery	Single-cell 3.7 V Li-Po/Li-Ion
GPIO current	7 mA maximum per pin
USB	Full-Speed native USB

3.3 V Logic Only

The MKR NB 1500 uses:

Do not assume UNO-style 5 V logic compatibility.

Before connecting a 5 V peripheral, check:

• its output voltage;
• its input HIGH threshold;
• I2C pull-up voltage;
• SPI voltage;
• UART voltage.

Use level shifting where required.

GPIO Current Limit

The official pinout specifies:

with group-level current limits as well.

Do not drive:

• relays;
• motors;
• solenoids;
• high-current LEDs;
• large buzzers;

directly from GPIO.

Main Digital Pin Mapping

The main MKR header exposes:

with the usual SAMD21 MKR mapping:

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

Analog Inputs A0-A6

The board exposes seven analogue inputs:

with digital aliases:

Analog pin	Digital alias	SAMD21 pin	Main function
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

ADC Resolution

The SAMD21 ADC supports Arduino read modes of:

For 12-bit readings:

Then:

returns approximately:

A0 Is a True DAC Output

A0 is also:

and can provide a genuine:

rather than PWM.

DAC Example

PWM Pins

The MKR NB 1500 uses the same general MKR/SAMD21 timer layout, with PWM available on pins including:

for 13 documented PWM-capable positions.

Hardware UART

The user-facing hardware UART is:

Use:

Serial vs Serial1

Because the SAMD21 has native USB:

This is useful when the board needs to communicate with a separate UART device while still debugging over USB.

I2C Pins

The main I2C bus is:

Use:

SPI Pins

The user-facing SPI bus is:

Use:

The Cellular Modem Uses Separate Internal Connections

The SARA-R410M-02B is not wired to the user-facing D13/D14 UART.

The board uses internal SAMD21 signals for modem control and communication, including:

So the external:

remains available for your own hardware.

SARA-R410M-02B Cellular Modem

The fitted modem is the:

designed for:

low-power wide-area cellular networks.

Supported LTE Bands

u-blox documents the multi-regional SARA-R410M-02B for LTE Cat M1/NB1 bands:

Actual operation still depends on:

• operator support;
• module firmware;
• regional certification;
• SIM provisioning;
• network coverage.

LTE-M vs NB-IoT

Both are cellular LPWAN technologies, but they target somewhat different use cases.

LTE-M

Typically offers:

• higher data rate;
• lower latency;
• better mobility support;
• more conventional TCP/IP applications.

NB-IoT

Typically emphasises:

• very low data rates;
• deep indoor coverage;
• low-power stationary sensors;
• small periodic telemetry.

Important: Do Not Rely on 2G EGPRS Fallback

Arduino’s current MKR NB 1500 overview contains a reference to:

but the fitted:

is documented by u-blox as:

only.

The closely related:

family is the variant that adds 2G EGPRS.

For a real deployment, plan MKR NB 1500 connectivity around:

rather than assuming 2G fallback.

SIM Card Required

The modem requires a compatible cellular SIM with service enabled for:

• LTE-M;
• NB-IoT;
• the operator APN and data plan you intend to use.

A normal consumer SIM may not necessarily have NB-IoT enabled.

Operator Support Matters More Than the Board

Before deploying the hardware, verify:

Antenna Is Essential

Fit a suitable cellular antenna to the board’s RF connector before normal modem use.

The antenna must support the LTE bands used by your operator.

Do not substitute a random:

and expect correct cellular performance.

MKRNB Library

Arduino provides the:

library for controlling the modem.

A minimal modem test starts with:

Connecting to the Cellular Network

A normal network application creates:

and starts the modem with the SIM PIN if required.

The APN and account settings depend on your carrier.

HTTPS and TCP/IP

The MKRNB library provides high-level client classes for network applications such as:

• HTTP;
• HTTPS;
• TCP;
• UDP;
• NTP;
• cloud telemetry.

Arduino’s official examples include:

Cellular Power Peaks Matter

Cellular radios draw current in short bursts when transmitting.

u-blox specifies peaks of around:

for the SARA-R410M during LTE transmission under worst-case conditions.

This is very different from the current draw of a sleeping SAMD21.

Why Weak Power Supplies Cause Modem Problems

An inadequate supply can cause:

• network registration failures;
• random resets;
• failed transmissions;
• modem brown-outs;
• intermittent operation under poor signal conditions.

The worse the radio link, the more important a stable supply becomes because the network may command higher transmitter power.

Li-Po Battery Support

The board includes onboard charging support for a:

This is especially useful because a battery can help supply short modem current peaks more effectively than a weak USB source.

Battery Size

Use a rechargeable cell that is compatible with the board’s charging system.

For cellular projects, practical battery sizing should consider:

• network registration time;
• transmit interval;
• signal strength;
• LTE-M vs NB-IoT mode;
• sleep current;
• sensor load.

ATECC508 Secure Element

The MKR NB 1500 includes an:

crypto device for:

• secure key storage;
• device identity;
• certificate operations;
• secure cloud authentication.

This is useful when the board sends data over public cellular networks.

Native USB

The SAMD21 provides native:

so the board can support:

• USB CDC serial;
• USB HID;
• other native USB classes supported by the Arduino core.

LED_BUILTIN

The main user LED is:

so normal Arduino Blink examples can use:

External Interrupts

Interrupt-capable pins include the usual MKR/SAMD21 group such as:

Use:

for portable Arduino code.

Common Mistake 1: Applying 5 V to GPIO

The board is a:

Use level shifting for incompatible peripherals.

Common Mistake 2: Assuming Any SIM Will Work

The SIM must be provisioned for:

on the network you intend to use.

Common Mistake 3: Assuming 2G Fallback

The fitted R410M-02B is an LTE Cat M1/NB1 modem.

Do not design around EGPRS fallback unless your exact hardware is a different modem variant.

Common Mistake 4: Ignoring Modem Current Peaks

A board that appears stable while idle can reset when the modem transmits.

Design the supply for:

not only the average current.

Common Mistake 5: Forgetting the Antenna

Do not repeatedly operate the cellular transmitter without the correct antenna attached.

Common Mistake 6: Confusing Serial1 with the Modem UART

Your external:

is separate from the modem’s internal communication link.

Quick Digital Reference

Quick Analog Reference

Quick Communications Reference

Final Thoughts

The MKR NB 1500 is essentially a SAMD21 Arduino combined with a purpose-built low-power cellular modem.

Its key hardware is:

The most important design rules are:

For remote IoT work, the hardest part is usually not the Arduino code. It is ensuring that the selected operator actually provides LTE-M or NB-IoT coverage at the deployment location and that the power system remains stable during modem transmission.

For the LoRa alternative in the same MKR form factor, see our MKR WAN 1310 pinout guide. For Wi-Fi/Bluetooth connectivity, see the MKR WiFi 1010 pinout guide. For the storage/audio-focused version, see our MKR Zero pinout guide.