Nano 33 BLE Python® Guide

The Nano 33 BLE board can be programmed using the popular Python® programming language. More specifically, it supports OpenMV's fork of MicroPython, where MicroPython is an implementation of the Python® language, designed to run on microcontrollers. In this article, you will find a lot of sample scripts that will work directly with your Nano 33 BLE, such as general GPIO control, reading data from the IMU module and testing Bluetooth® Low Energy connection.

• If you want to read more about Arduino & Python®, you can visit the Python® with Arduino article. Here you will find a lot of useful examples, such as how to use delays, interrupts, reading pins and more general functions.

If you are looking for information related to the similar Nano 33 BLE Sense board, you can refer to the Nano 33 BLE Sense Python® Guide.

Hardware & Software Needed

• Arduino Nano 33 BLE.
• OpenMV IDE

This guide does not cover the installation of OpenMV and MicroPython on your board. Please refer to Getting started with OpenMV and Nano 33 BLE for a detailed guide.

API

Below you will find a lot of useful examples that can be loaded to your Nano 33 BLE board. Many of these examples were extracted from the OpenMV repository, where you can find many useful examples for other boards as well.

In this article, you will only find examples for the Nano 33 BLE board. For more information on how to use delays, read and write to pins, please refer to the Python® with Arduino main article.

Pin Control

The pinout for the Nano 33 BLE and the NRF52840 microcontroller varies greatly. For example, if we are to use

D2

Copy
1# Defining "D2" on the Nano 33 BLE
2p0 = Pin(43, Pin.OUT)

In the MicroPython port of the Nano 33 BLE board, the pinout is the same as the Nordic NRF52840 (the microcontroller). You will find a GPIO Map below this section that explains how to address the different pins.

Pin Map

Before you start using the board's pins, it might be a good idea to check out the table below to understand the relationship between Arduino's pinout and the NRF52840's pinout.

Analog Pins

To read the analog pins on the Nano BLE , we can choose from the following pins:

• A0 -

  4

• A1 -

  5

• A2 -

  30

• A3 -

  29

• A4 -

  31

• A5 -

  2

• A6 -

  28

• A7 -

  3

To define them, we need to import the

machine

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1import machine
2
3adc_pin = machine.Pin(29)
4adc = machine.ADC(adc_pin)

To read the analog pin, simply use:

Copy
1reading = adc.read_u16() #16-bit resolution (0-65535)

The below script will read the

A3

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1import machine
2import time
3
4adc_pin = machine.Pin(29) # A3
5adc = machine.ADC(adc_pin)
6
7while True:
8    reading = adc.read_u16()     
9    print("ADC: ",reading)
10    time.sleep_ms(500)

LED Control

There are 3 different LEDs that can be accessed on the Nano BLE: RGB, the built-in LED and the power LED.

They can be accessed by importing the

LED

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1from board import LED
2
3led_red = LED(1) # red LED
4led_green = LED(2) # green LED
5led_blue = LED(3) # blue LED
6led_builtin = LED(4) # classic built-in LED (also accessible through pin 13)

To access the power LED we need to import the

Pin

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1from machine import Pin
2
3led_pwr = Pin(41, Pin.OUT)

RGB

Blink all RGB lights every 0.25 seconds.

Copy
1from board import LED
2import time 
3
4led_red = LED(1)
5led_green = LED(2)
6led_blue = LED(3)
7
8while (True):
9   
10    # Turn on LEDs
11    led_red.on()
12    led_green.on()
13    led_blue.on()
14
15    # Wait 0.25 seconds
16    time.sleep_ms(250)
17    
18    # Turn off LEDs
19    led_red.off()
20    led_green.off()
21    led_blue.off()
22
23    # Wait 0.25 seconds
24    time.sleep_ms(250)

Built-in LED

The classic blink example! Blink the built-in LED every 0.25 seconds.

Copy
1from board import LED
2import time 
3
4led_builtin = LED(4)
5
6while (True):
7   
8    # Turn on LED
9    led_builtin.on()
10
11    # Wait 0.25 seconds
12    time.sleep_ms(250)
13    
14    # Turn off LED
15    led_builtin.off()
16
17    # Wait 0.25 seconds
18    time.sleep_ms(250)

IMU (LSM9DS1)

Access the

accelerometer

magnetometer

gyroscope

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1import time
2import lsm9ds1
3from machine import Pin, I2C
4
5bus = I2C(1, scl=Pin(15), sda=Pin(14))
6lsm = lsm9ds1.LSM9DS1(bus)
7
8while (True):
9    #for g,a in lsm.iter_accel_gyro(): print(g,a)    # using fifo
10    print('Accelerometer: x:{:>8.3f} y:{:>8.3f} z:{:>8.3f}'.format(*lsm.read_accel()))
11    print('Magnetometer:  x:{:>8.3f} y:{:>8.3f} z:{:>8.3f}'.format(*lsm.read_magnet()))
12    print('Gyroscope:     x:{:>8.3f} y:{:>8.3f} z:{:>8.3f}'.format(*lsm.read_gyro()))
13    print("")
14    time.sleep_ms(500)

Bluetooth® Low Energy

This example allows us to connect to our board via our phone, and control the built-in LED. We recommend using the nRF Connect applications.

• nRF desktop
• nRF mobile

After loading the script below, your board should be listed as "Nano 33 BLE" in the list of available devices. You need to pair in order to control the built-in LED.

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1# Use nRF Connect from App store, connect to the Nano and write 1/0 to control the LED.
2
3import time
4from board import LED
5from ubluepy import Service, Characteristic, UUID, Peripheral, constants
6
7def event_handler(id, handle, data):
8    global periph
9    global service
10    if id == constants.EVT_GAP_CONNECTED:
11        pass
12    elif id == constants.EVT_GAP_DISCONNECTED:
13        # restart advertisement
14        periph.advertise(device_name="Nano 33 BLE", services=[service])
15    elif id == constants.EVT_GATTS_WRITE:
16        LED(1).on() if int(data[0]) else LED(1).off()
17
18# start off with LED(1) off
19LED(1).off()
20
21notif_enabled = False
22uuid_service = UUID("0x1523")
23uuid_led     = UUID("0x1525")
24
25service = Service(uuid_service)
26char_led = Characteristic(uuid_led, props=Characteristic.PROP_WRITE)
27service.addCharacteristic(char_led)
28
29periph = Peripheral()
30periph.addService(service)
31periph.setConnectionHandler(event_handler)
32periph.advertise(device_name="Nano 33 BLE", services=[service])
33
34while (True):
35    time.sleep_ms(500)

Summary

In this article we have gone through a selection of scripts that will help you control your Nano BLE board, via the OpenMV IDE. Feel free to check out our Python® with Arduino boards article, where you can find guides to other boards, useful links to learn Python® and more.