Arduino Nano 33 BLE Sense

Warning

This board is no longer supported. The last OpenMV firmware release for the Arduino Nano 33 BLE Sense is 4.7.0. No further firmware updates, bug fixes, or new features will be issued for this target. The information below is preserved for users running 4.7.0 or earlier.

The Arduino Nano 33 BLE Sense is a 45 × 18 mm Arduino‑Nano‑form‑factor sensor board built around the Nordic Semiconductor nRF52840 — a single ARM Cortex‑M4 with FPU running at 64 MHz with 256 KB of internal SRAM and 1 MB of internal flash. Bluetooth LE 5.0 (and 802.15.4) come from the SoftDevice running on the same SoC, and the board carries an integrated environmental and motion sensor cluster: 9‑axis IMU, barometer, temperature / humidity, ambient light / colour / proximity / gesture, and a PDM microphone.

The Nano 33 BLE Sense has no on‑board image sensor — the OpenMV firmware here is a sensors‑and‑audio build focused on the integrated peripherals plus support for external thermal cameras over I²C.

Arduino Nano 33 BLE Sense

For full datasheet, photos, and dimensions see the Arduino Nano 33 BLE Rev2 product page.

Highlights

  • Nordic nRF52840 Cortex‑M4 at 64 MHz with 256 KB internal SRAM and 1 MB internal flash (Softdevice s140 + OpenMV firmware + filesystem all share this 1 MB).

  • Bluetooth LE 5.0 plus IEEE 802.15.4 (Thread / Zigbee) via the on‑die radio and Nordic SoftDevice s140.

  • 9‑axis IMU — accelerometer + gyroscope + magnetometer. Rev 1 boards have an STMicro LSM9DS1; Rev 2 boards have a Bosch BMI270 plus a BMM150 magnetometer. The frozen imu module probes both at boot.

  • Pressure sensor — STMicro LPS22HB barometer (260–1260 hPa).

  • Temperature / humidity — HTS221 on Rev 1, HS3003 on Rev 2.

  • Light / colour / proximity / gesture — Broadcom APDS9960.

  • MEMS microphone — STMicro MP34DT05, captured through audio — Audio Module.

  • 20 user I/O pins on the standard Nano headers — D2–D13 (digital) plus A0–A7 (analog). Twelve PWM outputs.

  • Micro USB connector for power, programming, and a CDC REPL.

Note

The OpenMV firmware on the Nano 33 BLE Sense is a stripped‑down build compared with the OpenMV camera boards: there is no on‑board image sensor, no JPEG codec, no GPU, no Wi‑Fi, no networking stack, and no ML / TFLite inference. Bluetooth LE is available through the legacy ubluepy module (the modern bluetooth / aioble — Async BLE APIs are not enabled). Use the integrated sensors together with ulab.numpy for on‑device DSP and feature extraction.

Pinout

Arduino Nano 33 BLE Sense Pinout

Pin reference

Pin name

Reference

Function

RX (D0)

3.3 V

UART1 RX (Serial1) / P1.10

TX (D1)

3.3 V

UART1 TX (Serial1) / P1.03

D2

3.3 V

P1.11

D3

3.3 V

P1.12 (PWM‑capable)

D4

3.3 V

P1.15 (PWM‑capable)

D5

3.3 V

P1.13 (PWM‑capable)

D6

3.3 V

P1.14 (PWM‑capable)

D7

3.3 V

P0.23 (PWM‑capable)

D8

3.3 V

P0.21 (PWM‑capable)

D9

3.3 V

P0.27 (PWM‑capable)

D10

3.3 V

P1.02 (PWM‑capable)

D11

3.3 V

P1.01 / SPI0 COPI (PWM‑capable)

D12

3.3 V

P1.08 / SPI0 CIPO

D13

3.3 V

P0.13 / SPI0 SCK / LED_BUILTIN

A0

3.3 V

P0.04 / ADC IN2

A1

3.3 V

P0.05 / ADC IN3

A2

3.3 V

P0.30 / ADC IN6

A3

3.3 V

P0.29 / ADC IN5

A4

3.3 V

P0.31 / ADC IN7 / I2C0 SDA

A5

3.3 V

P0.02 / ADC IN0 / I2C0 SCL

A6

3.3 V

P0.28 / ADC IN4

A7

3.3 V

P0.03 / ADC IN1

RESET

3.3 V

press the on‑board RESET button or pull to GND to reset

LED_BUILTIN

3.3 V

Yellow LED on D13 (P0.13)

LED_RED

3.3 V

RGB LED red channel (active low) / P0.24

LED_GREEN

3.3 V

RGB LED green channel (active low) / P0.16

LED_BLUE

3.3 V

RGB LED blue channel (active low) / P0.06

LED_PWR

3.3 V

Green power LED / P1.09

Warning

The Nano 33 BLE Sense’s I/O pins are 3.3 V only — they are not 5 V tolerant. Driving 5 V into them will damage the nRF52840.

Power pins

  • VIN — 4.5 – 21 V input. Powers the board through the on‑board regulator.

  • +5V — switched 5 V from USB / VIN, available to power external shields. Disabled by default; cut the small VUSB jumper on the back to enable it.

  • +3V3 — 3.3 V regulator output (~50 mA available for shields).

  • AREF — analog reference input.

  • GND — common ground.

The Nano 33 BLE Sense can be powered through either path:

  • Micro USB — supplies 5 V to the on‑board regulator.

  • VIN pin — drive a regulated 4.5 – 21 V supply.

Recovery and debug pins

  • RESET — both an exposed pad and a momentary RESET button on the top of the board, tied to the nRF52840’s reset line.

The Nano 33 BLE Sense uses Arduino’s standard double‑tap reset to enter the on‑board mass‑storage bootloader. Quickly press the reset button twice — the board re‑enumerates over USB as a drive that accepts a .bin firmware image, and OpenMV IDE uses this mode to flash.

A running script can re‑enter the bootloader on demand by calling machine.bootloader():

import machine

machine.bootloader()

The nRF52840’s SWD signals are exposed on small pads on the back of the board (SWDIO, SWCLK, GND). They are 3.3 V referenced.

Onboard peripherals

LEDs

The Nano 33 BLE Sense has three indicator paths. The nrf port exposes them through a board‑specific LED class addressed by numeric ID:

LED id

Channel

LED(1)

Red (P0.24, active low)

LED(2)

Green (P0.16, active low)

LED(3)

Blue (P0.06, active low)

LED(4)

Yellow LED_BUILTIN (P0.13, active high)

 
from board import LED

LED(4).on()    # yellow user LED
LED(1).on()    # red

The green power LED on P1.09 is wired in hardware to the 3.3 V rail and is not addressable through LED — drive it directly via machine.Pin (alias "LED_PWR") if you want to use it as an extra status indicator.

IMU

The 9‑axis IMU is exposed through the frozen imu module, which auto‑detects whether the board has the original LSM9DS1 (Rev 1) or the BMI270 + BMM150 (Rev 2) and presents a unified IMU class. Pass it the internal I²C bus the sensors share (bus 1 on P0.14/P0.15):

import imu
import time
from machine import I2C, Pin

bus = I2C(1, scl=Pin(15), sda=Pin(14))
sensor = imu.IMU(bus)

while True:
    print(sensor.accel())   # (x, y, z) acceleration tuple
    print(sensor.gyro())    # (x, y, z) angular‑rate tuple
    print(sensor.magnet())  # (x, y, z) magnetometer tuple
    time.sleep_ms(100)

For direct access to a specific driver — useful when you need the IMU’s tap detection, FIFO, or lower‑level configuration — import the matching frozen driver (lsm9ds1, bmi270, bmm150) and instantiate it on the same internal I²C bus.

Environmental sensors

The pressure, temperature, and humidity sensors live on the same internal I²C bus as the IMU (bus 1, on P0.14/P0.15). The nrf port’s machine.I2C doesn’t auto‑bind to those pins, so pass them explicitly:

import time
from machine import I2C, Pin
from lps22h import LPS22H
from hts221 import HTS221             # Rev 1 (try first)
# from hs3003 import HS3003           # Rev 2

bus = I2C(1, scl=Pin(15), sda=Pin(14))
lps = LPS22H(bus)
try:
    hts = HTS221(bus)
except OSError:
    from hs3003 import HS3003
    hts = HS3003(bus)

while True:
    print("pressure: %.2f hPa" % lps.pressure())
    print("temperature: %.2f C" % lps.temperature())
    print("humidity: %.2f %%" % hts.humidity())
    time.sleep_ms(500)

Light / colour / proximity / gesture

The Broadcom APDS9960 supports ambient light, RGB colour, proximity, and gesture sensing on the same I²C bus. The frozen apds9960 package wraps it:

from time import sleep_ms
from machine import I2C, Pin
from apds9960 import uAPDS9960 as APDS9960

bus = I2C(1, scl=Pin(15), sda=Pin(14))
apds = APDS9960(bus)

apds.enableLightSensor()
while True:
    sleep_ms(250)
    print("ambient light:", apds.readAmbientLight())

Microphone

The on‑board MP34DT05 PDM microphone is captured through audio — Audio Module:

import audio
from ulab import numpy as np

def loudness(pcmbuf):
    samples = np.array(np.frombuffer(pcmbuf, dtype=np.int16), dtype=np.float)
    rms = np.sqrt(np.mean(samples ** 2))
    if rms > 10000:
        print("Loud!", int(rms))

audio.init(channels=1, frequency=16000, gain_db=24)
audio.start_streaming(loudness)

Bluetooth LE

The nRF52840’s Bluetooth LE radio (running on the Nordic SoftDevice s140) is exposed through the legacy ubluepy module. Advertise as a peripheral with a single Service / Characteristic:

from ubluepy import Service, Characteristic, UUID, Peripheral, constants
from board import LED

def event_handler(id, handle, data):
    if id == constants.EVT_GAP_CONNECTED:
        LED(2).on()                    # green LED on connect
    elif id == constants.EVT_GAP_DISCONNECTED:
        LED(2).off()
        periph.advertise(device_name="Nano 33", services=[svc])

svc = Service(UUID("181A"))            # Environmental Sensing
svc.addCharacteristic(Characteristic(UUID("2A6E"), props=0x12))   # read + notify
periph = Peripheral()
periph.addService(svc)
periph.setConnectionHandler(event_handler)
periph.advertise(device_name="Nano 33", services=[svc])

The aioble — Async BLE and bluetooth modules used by the OpenMV camera boards are not enabled in this firmware build.

External thermal cameras

The Nano 33 BLE Sense build wires fir — thermal sensor driver (fir == far infrared) to the internal I²C 0 bus on A4/A5. Plug an MLX90621, MLX90640, MLX90641, or AMG8833 thermal sensor onto those pins and read frames with:

import fir

fir.init(fir.FIR_MLX90640)
while True:
    ta, ir, fmin, fmax = fir.read_ir()
    print("scene min/max:", fmin, "/", fmax)

Bus reference

GPIO

Use machine.Pin to read or drive any of the silkscreened pins. Outputs are 3.3 V CMOS. Maximum 15 mA per pin; maximum 25 mA total across all GPIOs.

from machine import Pin

out = Pin("D2", Pin.OUT)
out.on()
out.off()
out.value(1)

inp = Pin("D3", Pin.IN, Pin.PULL_UP)
print(inp.value())

UART

Bus

TX

RX

UART1

TX

RX

The TX and RX pads on the silkscreen are also labelled D1 and D0 respectively. Inside MicroPython use the names TX/RX (the names D0/D1 are not exported):

from machine import UART

uart = UART(1, baudrate=115200)
uart.write("hello")
uart.read(5)

I²C

Bus

SCL

SDA

I2C0

A5

A4 (header pins)

I2C1

—

— (internal — IMU, baro, env, APDS9960)

 
from machine import I2C

i2c = I2C(0, freq=400_000)
i2c.scan()
i2c.writeto(0x76, b"hi")

Bus 1 is the internal sensor bus — it serves the IMU, barometer, environmental sensor, and APDS9960. machine.I2C(1) is what the frozen sensor drivers use; you can scan or talk to it from your own code, but be aware the addresses are already taken by the on‑board sensors.

SPI

Bus

MOSI

MISO

SCK

CS

SPI0

D11

D12

D13

—

Note

The SCK line shares D13 with the yellow LED_BUILTIN — running SPI will blink the LED in time with the bus clock.

The CS line is not driven by the SPI peripheral — configure any free GPIO as an output and toggle it manually around the transfer:

from machine import SPI
from machine import Pin

spi = SPI(0, baudrate=10_000_000)
cs = Pin("D9", Pin.OUT, value=1)   # CS is not driven by the SPI peripheral

cs.value(0)
spi.write(b"hello")
cs.value(1)

ADC

The nRF52840 has eight 12‑bit ADC channels (SAADC) exposed on A0–A7. read_u16 returns 0–65535 across 0–3.3 V at the pin:

from machine import ADC
import time

adc = ADC("A0")
while True:
    voltage = adc.read_u16() * 3.3 / 65535
    print(voltage)
    time.sleep_ms(100)

PWM

The nRF52840’s PWM peripheral can drive most user GPIOs. Drive any of the digital pins via machine.PWM:

from machine import Pin, PWM

pwm = PWM(Pin("D3"), freq=1_000, duty_u16=32768)

Software bit‑banged buses

machine.SoftI2C and machine.SoftSPI work on any GPIO if you need an extra bus.

Timing

time

The time module covers blocking delays, monotonic ticks, and elapsed‑time measurement:

import time

time.sleep(1)              # seconds
time.sleep_ms(500)
time.sleep_us(10)

start = time.ticks_ms()
# ...do work...
elapsed = time.ticks_diff(time.ticks_ms(), start)

Real‑time clock

machine.RTC keeps wall‑clock time across resets. The nRF52840’s RTC is tied to the on‑chip oscillator and does not survive full power loss — set the time on every cold boot if it matters to your application:

from machine import RTC

rtc = RTC()
rtc.datetime((2026, 4, 30, 4, 12, 0, 0, 0))   # Y, M, D, weekday, h, m, s, subsec
print(rtc.datetime())

Boot and runtime info

Firmware update (DFU)

The Nano 33 BLE Sense uses Arduino’s standard double‑tap reset to enter the on‑board mass‑storage bootloader (a single contiguous 128 KB at the top of flash, baked into the board at the factory). Quickly press the reset button twice — the board re‑enumerates over USB as a small drive named ARDUINO and OpenMV IDE flashes the firmware over that.

Filesystem and boot order

The Nano 33 BLE Sense firmware mounts a single filesystem on boot:

  • Internal flash — 64 KB partition mounted at /flash and used as the working directory. Holds main.py and README.txt by default; created on the very first boot.

After mounting, the interpreter then runs scripts from /flash:

  • boot.py is executed on every soft reset.

  • main.py is executed only on cold boot, immediately after boot.py.

The default main.py shipped on a freshly flashed board just blinks the yellow LED_BUILTIN as a heartbeat (two short pulses, short gap), so you can tell the firmware booted cleanly without any host attached.

When connected over USB, /flash enumerates as a USB mass‑storage drive on the host, letting you edit boot.py, main.py, and any other files directly. Eject the drive before resetting the board so the host flushes its cached writes.

Software libraries

See the library index for the full list of modules — including which ones are unique to the Nano 33 BLE Sense build.