Adafruit MQTT in CircuitPython Instruction Manual

MQTT in CircuitPython

Created by Brent Rubell

Last updated on 2021-02-09 02:53:46 PM EST

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Guide Contents

Guide Contents Overview Parts

All-in-One CircuitPython WiFi Boards Externally Connected CircuitPython Network Hardware

WiFi Ethernet

CircuitPython Setup

Install CircuitPython CircuitPython Library Installation

Connecting to the Adafruit IO MQTT Broker

Obtain Adafruit IO Username and Key Create Adafruit IO Feeds Create an Adafruit IO Dashboard Create a Gauge Block Create a Toggle Switch Block

CircuitPython WiFi Usage

Internet Connect! Secrets File Setup for Adafruit IO Code Usage

ESP32-S2 Code ESP32 AirLift Code

(Optional) Change ESP32 AirLift Pinouts

Feed Publishing Example Feed Subscription Example Going Further - the Adafruit IO CircuitPython Module

CircuitPython Ethernet Usage

Ethernet Setup Connect Ethernet Cable Code Usage Feed Publishing Example Feed Subscription Example Going Further - the Adafruit IO CircuitPython Module

CircuitPython Cellular Usage

Cellular Data Setup Connect FONA Code Usage Feed Publishing Example Feed Subscription Example Going Further - the Adafruit IO CircuitPython Module

Connecting to a MQTT Broker

Commercial Brokers Self-Hosted Brokers Secrets File Setup Code MiniMQTT Port Configuration Code Usage

Code Walkthrough

MiniMQTT Callback Methods

Advanced MiniMQTT Usage MiniMQTT Loop

loop

42 42 42

MiniMQTT Client Identifier MiniMQTT Logging MiniMQTT Last Will and Testament

Overview

So, you have a CircuitPython project and want to connect it to the internet? You may want to consider

adding MQTT to your project. MQTT is an extremely popular and lightweight protocol which can connect

your project to the internet and quickly process network events.

MQTT (https://adafru.it/pYc) is a small, lightweight protocol which is incredibly easy to use in scenarios

where bandwidth is at a premium, your project is sending a small amount of data every so often, or if you'd like to process network events incredibly quickly (clicking a button would cause your project to do something).

If you'd like to learn more about MQTT - check out its section in the All The Internet of Things:

Protocols guide (https://adafru.it/Fmp).

We've built a robust MQTT module for CircuitPython called CircuitPython

MiniMQTT (https://adafru.it/Fmq) to quickly get you started connecting your projects to the internet and

sending data around.

In this guide, you will set up your CircuitPython board with the necessary libraries, connect to the

internet and connect your CircuitPython board to either a MQTT broker of your choice or the free

Adafruit IO MQTT broker. We've included code-walkthrough and advanced usage sections to this guide

so you can roll your own MiniMQTT project!

Parts

You'll need a CircuitPython board which either has network connectivity built-in or external network hardware .

All-in-One CircuitPython WiFi Boards

Don't want to add extra hardware to your project?

Consider grabbing a board which has an ESP32 WiFi

co-processor built-in!

Adafruit Metro M4 Express AirLift (WiFi) - Lite

Give your next project a lift with AirLift - our witty name for the ESP32 co-processor that graces this Metro M4. You already know about the Adafruit Metro... $34.95 In Stock

Add to Cart

Adafruit PyPortal - CircuitPython Powered Internet Display

PyPortal, our easy-to-use IoT device that allows you to create all the things for the “Internet of Things” in minutes. Make custom touch screen interface... $54.95 In Stock

Externally Connected CircuitPython Network Hardware

If you already have a project which uses a CircuitPython board without internet connectivity, you can easily add WiFi connectivity with an externally connected AirLift module.

WiFi

If you're using an Adafruit Feather , adding WiFi connectivity to your project is as easily as snapping the

the AirLift FeatherWing on top.

Adafruit AirLift FeatherWing – ESP32 WiFi Co-Processor

Give your Feather project a lift with the Adafruit AirLift FeatherWing - a FeatherWing that lets you use the powerful ESP32 as a WiFi co-processor. You probably have your... $12.95 In Stock

If you're using a CircuitPython board with an Arduino form-factor , you'll want to pick up an AirLift Shield.

Add to Cart

Adafruit AirLift Shield - ESP32 WiFi Co-Processor

Give your Arduino project a lift with the Adafruit AirLift Shield - a shield that lets you use the powerful ESP32 as a WiFi co-processor. You probably have your favorite... $14.95 In Stock

If none of the form factors above work for your project - we also have a breakout board which can connect to any microcontroller over SPI.

Add to Cart

Adafruit AirLift – ESP32 WiFi Co-Processor Breakout Board

Give your plain ol' microcontroller project a lift with the Adafruit AirLift - a breakout board that lets you use the powerful ESP32 as a WiFi co-processor. You probably... $9.95 In Stock

Ethernet

Wireless is wonderful, but sometimes you want the strong reliability of a wired connection. If your project is going to be part of a permanent installation, you'll want to add ethernet networking to your project.

For more information about using Ethernet for CircuitPython with Wiznet5k, please see our guide

here... (https://adafru.it/JEp)

Add to Cart

Adafruit Ethernet FeatherWing

Wireless is wonderful, but sometimes you want the strong reliability of a wire. If your Feather board is going to be part of a permanent installation, this Ethernet... $19.95 In Stock

Add to Cart

Ethernet Shield for Arduino - W5500 Chipset

The W5500 Ethernet Shield for Arduino from Seeed Studio is a great way to set up your projects with internet connectivity with just a single chip. Similar to the $32.50 In Stock

Particle Ethernet FeatherWing

This three-in-one Particle Ethernet Feather is a mix of our Ethernet 'wing and the $20.00 In Stock

Add to Cart

CircuitPython Setup

MQTT devices, like your CircuitPython board, connect to a broker with a client library.

We've written an awesome CircuitPython MQTT client library called Adafruit

MiniMQTT (https://adafru.it/Fm2).

This library is based off previous work by pfalcon on uMQTT (https://adafru.it/Fm3) (and the umqtt port to

ESP32SPI by beachbc (https://adafru.it/Fm4)). MiniMQTT's primary difference from MicroPython's uMQTT

library is its use of calling conventions and method names

similar

to The Eclipse

Foundation's Paho.Mqtt.Python (https://adafru.it/Fm5).

Install CircuitPython

Some CircuitPython compatible boards come with CircuitPython installed. Others are

CircuitPython-ready

, but need to have it installed. As well, you may want to update the version of CircuitPython already installed on your board. The steps are the same for installing and updating.

To install (or update) your CircuitPython board, follow this page and come back here when you've

successfully installed (or updated) CircuitPython. (https://adafru.it/Amd)

CircuitPython Library Installation

To interface your AirLift breakout/board with and the internet - you'll need to install a few CircuitPython libraries on your board.

First make sure you are running the latest version of Adafruit CircuitPython (https://adafru.it/tBa) for your board.

Next you'll need to install the necessary libraries to use the hardware--carefully follow the steps to find and install these libraries from Adafruit's CircuitPython library bundle (https://adafru.it/zdx) matching your version of CircuitPython.

CircuitPython hardware shows up on your computer operating system as a flash drive when connected via usb. The flash drive is called CIRCUITPY and contains a number of files. You will need to add additional files to enable the features of this project.

First, create a folder on the drive named lib if it is not already there.

Ensure your board's lib folder has the following files and folders copied over. The version of the files must be the same major version as your version of CircuitPython (i.e. 4.x for 4.x, 5.x for 5.x, etc.)

adafruit_minimqtt

Connecting to the Adafruit IO MQTT Broker

If you do not want to host your own MQTT broker, using Adafruit IO (https://adafru.it/eZ8)'s MQTT broker is a great way to get started connecting your CircuitPython project to the internet. Best of all -

it's free to use!

You're going to build an Adafruit IO Dashboard which can visualize incoming data from your CircuitPython board, and send data to it.

Obtain Adafruit IO Username and Key

If you have not already, sign up for an Adafruit IO account by clicking this link (https://adafru.it/Fm6).

Next, you're going to need your Adafruit IO username and secret API key.

Navigate to your profile (https://adafru.it/fsU) and click the View AIO Key button to retrieve them. Write

them down in a safe place, you'll need them later.

Create Adafruit IO Feeds

Adafruit IO uses a special type of MQTT Topic named a Feed to store data along with metadata (information about the data). You'll be publishing data to one feed, and subscribing to another.

Create two new Adafruit IO Feeds named

onoff

and

photocell

.

photocell

- This feed will store light data

published

from

your device to Adafruit IO onoff - This feed will act as an on/off switch, publishing data to your device from Adafruit IO

If you have not created an Adafruit IO Feed before, follow

this page and come back once you've the created two feeds above (https://adafru.it/f5k).

Create an Adafruit IO Dashboard

Adafruit IO Dashboards (https://adafru.it/f5m) are a way to interact with feeds. You can link

blocks

on dashboards to your feeds. The blocks can either display information about the feed (such as the current temperature) or allow you to interact with a feed by setting it to different values.

Start by creating a new dashboard . Name it whatever you'd like!

If you do not know how to create a dashboard , head over to this page and come back here when

you've successfully created a dashboard. (https://adafru.it/Fm7)

Create a Gauge Block

After creating a dashboard, create a Gauge Block to display the value of the Photocell feed.

Choose the

photocell

feed

Change the block title to

Photocell

Set the Gauge Minimum Value to

0

Set the Gauge Maximum Value to

1024

If you do not know how to add blocks to a dashboard, head

to over this page and come back when you've added a gauge block to your dashboard. (https://adafru.it/DZe)

Create a Toggle Switch Block

To send values to the

onoff

feed you created - create a toggle

switch block.

Choose the

onoff

feed

Set the block title to

On/Off

Set the Button On Text to

ON

Set the Button Off Text to

OFF

Your dashboard should look like the following:

CircuitPython WiFi Usage

Internet Connect!

Once you have CircuitPython setup and libraries installed, you can get your project connected to the Internet over WiFi.

To do this, you'll be editing CircuitPython code and will need an editor. We suggest using Mu, a lightweight text editor with support for CircuitPython built-in.

Click the button below to get instructions on how to install the Mu Editor.

https://adafru.it/ANO

If you have not yet connected your CircuitPython WiFi board to the Internet, follow one of the guides below and come back when you've successfully connected to the internet:

If you have an ESP32-S2 board (such as the MagTag), follow this page to connect to the

internet (https://adafru.it/Qgb).

If you have an AirLift All-in-One board (such as the PyPortal), follow this page to connect to the

internet (https://adafru.it/Eao).

If you have an externally connected AirLift (such as the AirLift FeatherWing or AirLift breakout) ,

follow this page to connect to the internet (https://adafru.it/EF-).

 Before continuing, make sure you've connected your CircuitPython board to the internet by following the steps above

Secrets File Setup for Adafruit IO

While you created a secrets.py file and connected to the internet in the previous step, you'll need to edit the secrets.py file to include your Adafruit IO Username and Secret Key.

Add the following code to your secrets.py file, replacing _your_adafruit_io_username with your Adafruit IO

username.

Then, replace _your_big_huge_super_long_aio_key_ with your Adafruit IO Active Key.

secrets = { 'ssid' : '_your_wifi_ssid_', 'password' : '_your_wifi_password_', 'aio_username' : '_your_adafruit_io_username_', 'aio_key' : '_your_big_huge_super_long_aio_key_' }

Make sure you save this file before proceeding as secrets.py in the root directory of your board CIRCUITPY drive.

Code Usage

ESP32-S2 Code

CircuitPython boards using the ESP32- S2 such as the MagTag (https://adafru.it/OMb) or Metro ESP32-

S2 (https://adafru.it/Qgc) have internet connectivity built into the CircuitPython firmware.

https://adafru.it/ANO

Copy the following code to your code.py file on your microcontroller:

 You will need MiniMQTT version 5.0.0 or later AND CircuitPython 6.2.0-beta.1 to work with the ESP32-S2.

Temporarily unable to load content:

ESP32 AirLift Code

CircuitPython boards using an ESP32 "AirLift" Co-Processor such as the PyPortal (https://adafru.it/pyportal) require a helper library to connect to the internet.

Copy the following code to your code.py file on your microcontroller:

Temporarily unable to load content:

(Optional) Change ESP32 AirLift Pinouts

If you are using a board with a built-in ESP32 (like the PyPortal), you do not need to make changes to the code. It's already setup for usage with those boards. However, if you are using an externally connected ESP32 (like the AirLift Breakout), you'll need to define the ESP32's pinouts.

Make sure to change the ESP32 pin definitions in the code to match your wiring . You can do this by uncommenting and editing the following lines in your code to match your wiring.

esp32_cs = DigitalInOut(board.D9) esp32_ready = DigitalInOut(board.D10) esp32_reset = DigitalInOut(board.D5)

Feed Publishing Example

Directly after saving the code.py file, open a serial monitor/REPL to see the output. It should look something like the following:

code.py output: Connecting to Adafruit IO... Connected to Adafruit IO! Listening for topic changes on brubell/feeds/onoff Sending photocell value: 0... Sent! Sending photocell value: 1... Sent! Sending photocell value: 2... Sent! Sending photocell value: 3... Sent!

Navigate to the dashboard you created earlier. You should see the photocell gauge increasing its value as your CircuitPython device publishes the increasing photocell value to Adafruit IO.

If you navigate to the page for the photocell feed , you'll see the values increasing there along with metadata about when the data was received by the Adafruit IO broker.

Feed Subscription Example

While we're publishing the increasing

photocell

value to Adafruit IO - our code also

subscribes

to changes

on the

onoff

feed.

The example

code.py

subscribes to the

onoff

feed when the client successfully connects to Adafruit IO.

You don't need to make any changes to your code!

With the code still running on your CircuitPython device - click the toggle switch to send a value to the

onoff

feed. You should see the value appear on your serial monitor/REPL.

If you

really

want to see the speed of MQTT - remove the one second delay in the while True loop.

Change the following code (within while True ) from:

print('Sent!') photocell_val += 1

time.sleep(1)

to

print('Sent!') photocell_val += 1

time.sleep(0.5)

Be warned - if you do this you will not be able to run the code for very long. This is because Adafruit IO's MQTT server imposes a rate limit to prevent excessive load on the service.

The current Adafruit IO Data Rate is at most 1 request per second (or 60 requests within 60 seconds), without an Adafruit IO+ Boost applied to your account.

Going Further - the Adafruit IO CircuitPython Module

While you

can

use this code to communicate with Adafruit IO, the recommend method of using

CircuitPython with Adafruit IO is with the Adafruit IO CircuitPython module (https://adafru.it/EFZ).

This module has methods to simplify using the Adafruit IO MQTT API. It also includes helper features to make your experience using Adafruit IO better.

If you want to use Adafruit IO and CircuitPython, check out Adafruit IO CircuitPython (https://adafru.it/Fm8) and its code examples (https://adafru.it/Fm9) on GitHub!

CircuitPython Ethernet Usage

Ethernet Setup

This page assumes you've set up and connected your CircuitPython board to an Ethernet connection.

If you have not connected to the internet using Ethernet yet, please follow this guide and come back

to this page when you've successfully connected to the internet (https://adafru.it/JE-)

Connect Ethernet Cable

Make sure you have your Ethernet FeatherWing or Ethernet Shield firmly plugged into your hardware, and an Ethernet cable connected to your router or switch.

Code Usage

Copy the following code to a file on your computer. Name the file code.py. With your operating system file explorer/finder, copy this file to the CIRCUITPY drive which appears when your microcontroller board is plugged in via USB.

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT

import time import board import busio from digitalio import DigitalInOut

from adafruit_wiznet5k.adafruit_wiznet5k import WIZNET5K import adafruit_wiznet5k.adafruit_wiznet5k_socket as socket

import adafruit_minimqtt.adafruit_minimqtt as MQTT

# Get Adafruit IO details and more from a secrets.py file try: from secrets import secrets

except ImportError: print("Adafruit IO secrets are kept in secrets.py, please add them there!") raise

cs = DigitalInOut(board.D10) spi_bus = busio.SPI(board.SCK, MOSI=board.MOSI, MISO=board.MISO)

# Initialize ethernet interface with DHCP eth = WIZNET5K(spi_bus, cs)

### Feeds ###

# Setup a feed named 'photocell' for publishing to a feed photocell_feed = secrets["aio_username"] + "/feeds/photocell"

# Setup a feed named 'onoff' for subscribing to changes onoff_feed = secrets["aio_username"] + "/feeds/onoff"

### Code ###

# Define callback methods which are called when events occur # pylint: disable=unused-argument, redefined-outer-name def connected(client, userdata, flags, rc): # This function will be called when the client is connected # successfully to the broker. print("Connected to Adafruit IO! Listening for topic changes on %s" % onoff_feed) # Subscribe to all changes on the onoff_feed. client.subscribe(onoff_feed)

def disconnected(client, userdata, rc): # This method is called when the client is disconnected print("Disconnected from Adafruit IO!")

def message(client, topic, message): # This method is called when a topic the client is subscribed to # has a new message. print("New message on topic {0}: {1}".format(topic, message))

# Initialize MQTT interface with the ethernet interface MQTT.set_socket(socket, eth)

# Set up a MiniMQTT Client # NOTE: We'll need to connect insecurely for ethernet configurations. mqtt_client = MQTT.MQTT( broker="io.adafruit.com", username=secrets["aio_username"], password=secrets["aio_key"], is_ssl=False, )

# Setup the callback methods above mqtt_client.on_connect = connected mqtt_client.on_disconnect = disconnected mqtt_client.on_message = message

# Connect the client to the MQTT broker. print("Connecting to Adafruit IO...") mqtt_client.connect()

photocell_val = 0

while True: # Poll the message queue mqtt_client.loop()

# Send a new message print("Sending photocell value: %d..." % photocell_val) mqtt_client.publish(photocell_feed, photocell_val) print("Sent!") photocell_val += 1 time.sleep(5)

Feed Publishing Example

Directly after saving the code.py file, open a serial monitor/REPL to see the output. It should look something like the following:

code.py output: Connecting to Adafruit IO... Connected to Adafruit IO! Listening for topic changes on brubell/feeds/onoff Sending photocell value: 0... Sent! Sending photocell value: 1... Sent! Sending photocell value: 2... Sent! Sending photocell value: 3... Sent!

Navigate to the dashboard you created earlier. You should see the photocell gauge increasing its value as your CircuitPython device publishes the increasing photocell value to Adafruit IO.

If you navigate to the page for the photocell feed , you'll see the values increasing there along with metadata about when the data was received by the Adafruit IO broker.

Feed Subscription Example

While we're publishing the increasing

photocell

value to Adafruit IO - our code also

subscribes

to changes

on the

onoff

feed.

The example code.py subscribes to the

onoff

feed when the client successfully connects to Adafruit IO.

You don't need to make any changes to your code!

With the code still running on your CircuitPython device - click the toggle switch to send a value to the

onoff

feed. You should see the value appear on your serial monitor/REPL.

If you

really

want to see the speed of MQTT - remove the one second delay in the while True loop.

Change the following code (within while True ) from:

print('Sent!') photocell_val += 1

time.sleep(1)

to

print('Sent!') photocell_val += 1

time.sleep(0.5)

Be warned - if you do this you will not be able to run the code for very long. This is because Adafruit IO's MQTT server imposes a rate limit to prevent excessive load on the service.

The current Adafruit IO Data Rate is at most 1 request per second (or 60 requests within 60 seconds), without an Adafruit IO+ Boost applied to your account.

Going Further - the Adafruit IO CircuitPython Module

While you

can

use this code to communicate with Adafruit IO, the recommended method of using

CircuitPython with Adafruit IO is with the Adafruit IO CircuitPython module (https://adafru.it/EFZ).

This module has methods to simplify using the Adafruit IO MQTT API. It also includes helper features to make your experience using Adafruit IO better.

If you want to use Adafruit IO and CircuitPython, check out Adafruit IO CircuitPython (https://adafru.it/Fm8) and the code example for Ethernet (https://adafru.it/KVc)on GitHub!

CircuitPython Cellular Usage

Cellular Data Setup

This page assumes you've set up and connected your CircuitPython board to a cellular data connection.

If you have not connected to the internet using cellular data yet, please follow this guide and come

back when you've successfully connected. (https://adafru.it/La-)

Connect FONA

Make sure you have attached a LiPoly battery, GSM antenna, GPS antenna to your FONA.

You must also have a SIM card inserted in the FONA to use the module with cellular data.

If you haven't done this yet, navigate to this page and come back when you've set up the

FONA (https://adafru.it/KVF).

Code Usage

Copy the following code to a file on your computer. Name the file code.py. With your operating system file explorer/finder, copy this file to the CIRCUITPY drive which appears when your microcontroller board is plugged in via USB.

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT

import time import board import busio import digitalio from adafruit_fona.adafruit_fona import FONA import adafruit_fona.adafruit_fona_network as network import adafruit_fona.adafruit_fona_socket as socket

import adafruit_minimqtt.adafruit_minimqtt as MQTT

# Get Adafruit IO details and more from a secrets.py file try: from secrets import secrets except ImportError: print("GPRS secrets are kept in secrets.py, please add them there!") raise

### Cellular ###

# Create a serial connection for the FONA connection uart = busio.UART(board.TX, board.RX) rst = digitalio.DigitalInOut(board.D4) # Initialize FONA fona = FONA(uart, rst)

### Feeds ###

# Setup a feed named 'photocell' for publishing to a feed photocell_feed = secrets["aio_username"] + "/feeds/photocell"

# Setup a feed named 'onoff' for subscribing to changes onoff_feed = secrets["aio_username"] + "/feeds/onoff"

### Code ###

# Define callback methods which are called when events occur # pylint: disable=unused-argument, redefined-outer-name def connected(client, userdata, flags, rc): # This function will be called when the client is connected # successfully to the broker. print("Connected to Adafruit IO! Listening for topic changes on %s" % onoff_feed) # Subscribe to all changes on the onoff_feed. client.subscribe(onoff_feed)

def disconnected(client, userdata, rc): # This method is called when the client is disconnected print("Disconnected from Adafruit IO!")

def message(client, topic, message): # This method is called when a topic the client is subscribed to # has a new message. print("New message on topic {0}: {1}".format(topic, message))

# Initialize cellular data network network = network.CELLULAR( fona, (secrets["apn"], secrets["apn_username"], secrets["apn_password"]) )

while not network.is_attached: print("Attaching to network...") time.sleep(0.5) print("Attached!")

while not network.is_connected: print("Connecting to network...") network.connect() time.sleep(0.5) print("Network Connected!")

# Initialize MQTT interface with the cellular interface MQTT.set_socket(socket, fona)

# Set up a MiniMQTT Client # NOTE: We'll need to connect insecurely for ethernet configurations. mqtt_client = MQTT.MQTT( broker="io.adafruit.com", username=secrets["aio_username"], password=secrets["aio_key"], is_ssl=False, )

# Setup the callback methods above mqtt_client.on_connect = connected mqtt_client.on_disconnect = disconnected mqtt_client.on_message = message

# Connect the client to the MQTT broker. print("Connecting to Adafruit IO...") mqtt_client.connect()

photocell_val = 0 while True: # Poll the message queue mqtt_client.loop()

# Send a new message print("Sending photocell value: %d..." % photocell_val) mqtt_client.publish(photocell_feed, photocell_val) print("Sent!") photocell_val += 1 time.sleep(5)

Feed Publishing Example

Directly after saving the code.py file, open a serial monitor/REPL to see the output. It should look something like the following:

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable. code.py output: Attaching to network... Attached to network! Connecting to network... Connected to network! Connecting to Adafruit IO... Connected to Adafruit IO! Listening for topic changes on brubell/feeds/onoff Sending photocell value: 0... Sent! Sending photocell value: 1... Sent! Sending photocell value: 2... Sent! Sending photocell value: 3... Sent!

Navigate to the dashboard you created earlier. You should see the photocell gauge increasing its value as your CircuitPython device publishes the increasing photocell value to Adafruit IO.

If you navigate to the page for the photocell feed , you'll see the values increasing there along with metadata about when the data was received by the Adafruit IO broker.

Feed Subscription Example

While we're publishing the increasing

photocell

value to Adafruit IO - our code also

subscribes

to changes

on the

onoff

feed.

The example code.py subscribes to the

onoff

feed when the client successfully connects to Adafruit IO.

You don't need to make any changes to your code!

With the code still running on your CircuitPython device - click the toggle switch to send a value to the

onoff

feed. You should see the value appear on your serial monitor/REPL.

If you

really

want to see the speed of MQTT - remove the one second delay in the while True loop.

Change the following code (within while True ) from:

print('Sent!') photocell_val += 1

time.sleep(1)

to

print('Sent!') photocell_val += 1

time.sleep(0.5)

Be warned - if you do this you will not be able to run the code for very long. This is because Adafruit IO's MQTT server imposes a rate limit to prevent excessive load on the service.

The current Adafruit IO Data Rate is at most 1 request per second (or 60 requests within 60 seconds), without an Adafruit IO+ Boost applied to your account.

Going Further - the Adafruit IO CircuitPython Module

While you

can

use this code to communicate with Adafruit IO, the recommended method of using

CircuitPython with Adafruit IO is with the Adafruit IO CircuitPython module (https://adafru.it/EFZ).

This module has methods to simplify using the Adafruit IO MQTT API. It also includes helper features to make your experience using Adafruit IO better.

If you want to use Adafruit IO and CircuitPython, check out Adafruit IO

CircuitPython (https://adafru.it/Fm8) and the code example for Ethernet (https://adafru.it/JF0) on GitHub!

Connecting to a MQTT Broker

You can connect your CircuitPython device to any MQTT broker of your choice. MQTT brokers generally fall in three categories: Commercial hosted (Paid), Free hosted (Adafruit IO's MQTT broker lives on servers owned by Adafruit - we have a free tier), or Free and self-hosted (bring your own server!).

Commercial Brokers

These large-scale commercial (paid) brokers come with a higher data-rate speed and usually include device management features.

These brokers can also connect to CircuitPython devices running MiniMQTT. The primary advantage of using one of these services over your own broker or Adafruit IO is integration with a larger

suite

of cloudhosted tools. For example, if you are sending data to an Azure IoT Hub via MQTT, you could visualize sensor data using PowerBI or run machine learning models on it from Azure.

Self-Hosted Brokers

There are plenty of tools out there to host your own MQTT broker. We like Eclipse's

Mosquitto (https://adafru.it/pey) - it's an open-source broker which implements the MQTT protocol. There

are images for Mac, Linux, Windows and Raspberry Pi.

Secrets File Setup

While you created a secrets file and connected to the Internet in the previous step, you'll need to edit the secrets.py file to include information about your MQTT broker.

Add the following code to your secrets.py file, replacing _your_broker_url_or_ip with the URL or IP

Address of the MQTT broker you'd like to connect to.

If your MQTT broker requires authentication, replace _your_mqtt_broker_username_ with the username you use to log into the broker.

Then, replace _your_mqtt_broker_password_ with the password you use to authenticate your username with the broker.

If your MQTT broker does not require authentication, you may remove these fields.

secrets = { 'ssid' : '_your_wifi_ssid_', 'password' : '_your_wifi_password_', 'broker' : '_your_mqtt_broker_url_or_ip', 'user' : '_your_mqtt_broker_username_', 'pass' : '_your_mqtt_broker_password_' }

Code

Copy the following code to your code.py file on your microcontroller:

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT

import ssl import socketpool import wifi import adafruit_minimqtt.adafruit_minimqtt as MQTT

# Add a secrets.py to your filesystem that has a dictionary called secrets with "ssid" and # "password" keys with your WiFi credentials. DO NOT share that file or commit it into Git or other # source control. # pylint: disable=no-name-in-module,wrong-import-order try: from secrets import secrets except ImportError: print("WiFi secrets are kept in secrets.py, please add them there!") raise

# Set your Adafruit IO Username and Key in secrets.py # (visit io.adafruit.com if you need to create an account, # or if you need your Adafruit IO key.) aio_username = secrets["aio_username"] aio_key = secrets["aio_key"]

print("Connecting to %s" % secrets["ssid"]) wifi.radio.connect(secrets["ssid"], secrets["password"]) print("Connected to %s!" % secrets["ssid"])

### Topic Setup ###

# MQTT Topic # Use this topic if you'd like to connect to a standard MQTT broker mqtt_topic = "test/topic"

# Adafruit IO-style Topic # Use this topic if you'd like to connect to io.adafruit.com # mqtt_topic = secrets["aio_username"] + '/feeds/temperature'

### Code ### # Define callback methods which are called when events occur # pylint: disable=unused-argument, redefined-outer-name def connect(mqtt_client, userdata, flags, rc): # This function will be called when the mqtt_client is connected # successfully to the broker. print("Connected to MQTT Broker!") print("Flags: {0}\n RC: {1}".format(flags, rc))

def disconnect(mqtt_client, userdata, rc): # This method is called when the mqtt_client disconnects # from the broker. print("Disconnected from MQTT Broker!")

def subscribe(mqtt_client, userdata, topic, granted_qos): # This method is called when the mqtt_client subscribes to a new feed. print("Subscribed to {0} with QOS level {1}".format(topic, granted_qos))

def unsubscribe(mqtt_client, userdata, topic, pid): # This method is called when the mqtt_client unsubscribes from a feed. print("Unsubscribed from {0} with PID {1}".format(topic, pid))

def publish(mqtt_client, userdata, topic, pid): # This method is called when the mqtt_client publishes data to a feed. print("Published to {0} with PID {1}".format(topic, pid))

def message(client, topic, message):

# Method callled when a client's subscribed feed has a new value. print("New message on topic {0}: {1}".format(topic, message))

# Create a socket pool pool = socketpool.SocketPool(wifi.radio)

# Set up a MiniMQTT Client mqtt_client = MQTT.MQTT( broker=secrets["broker"], port=secrets["port"], username=secrets["aio_username"], password=secrets["aio_key"], socket_pool=pool, ssl_context=ssl.create_default_context(), )

# Connect callback handlers to mqtt_client mqtt_client.on_connect = connect mqtt_client.on_disconnect = disconnect mqtt_client.on_subscribe = subscribe mqtt_client.on_unsubscribe = unsubscribe mqtt_client.on_publish = publish mqtt_client.on_message = message

print("Attempting to connect to %s" % mqtt_client.broker) mqtt_client.connect()

print("Subscribing to %s" % mqtt_topic) mqtt_client.subscribe(mqtt_topic)

print("Publishing to %s" % mqtt_topic) mqtt_client.publish(mqtt_topic, "Hello Broker!")

print("Unsubscribing from %s" % mqtt_topic) mqtt_client.unsubscribe(mqtt_topic)

print("Disconnecting from %s" % mqtt_client.broker) mqtt_client.disconnect()

Before running your code, you'll need to make a few small changes for your configuration.

First, replace mqtt_topic with the mqtt topic you'd like to subscribe to . For example, if you are building a weather station and want to subscribe to its temperature.

Change the mqtt_topic from

mqtt_topic = 'test/topic'

to

mqtt_topic= 'weatherstation/temperature'

For more information about MQTT topic naming, check out this page here (https://adafru.it/Fmb).

MiniMQTT Port Configuration

By default, MiniMQTT connects to port 8883 (Secure/SSL). If you'd like to connect to a different port on the broker, use the following code to initialize the client.

# Set up a MiniMQTT Client client = MQTT.MQTT(broker = secrets['broker'], username = secrets['user'], password = secrets['pass'], port = 1883)

Code Usage

After setting up your topic and broker configuration, it's time to connect. Save the code.py file and open the serial monitor.

The client attempts to connect to the MQTT broker you specified.

Attempting to connect to io.adafruit.com Connected to MQTT Broker! Flags: 0 RC: 0

The client subscribes to the mqtt_topic you specified.

Subscribed to user/topic with QOS level 1

And notifies you that it subscribed to mqtt_topic with a quality of service level of 1. You can set the quality of service level by modifying the call to subscribe (read the docs about this method

here (https://adafru.it/Fmc)).

For more about the MQTT quality of service level - check out this page (https://adafru.it/Fmd)

The client publishes the string

Hello Broker

to the mqtt_topic .

Published to user/topic with PID 11

The client unsubscribes from the mqtt_topic .

Unsubscribed from user/topic with PID 22

Finally, the client disconnects from the MQTT broker

Disconnected from MQTT Broker!

The code tests all the primary methods of the MiniMQTT client. We'll walk through the code to understand how this example works.

Code Walkthrough

The code first connects the ESP32 to the wireless network you specified in the secrets.py file on your CIRCUITPY drive.

# Connect to WiFi wifi.connect()

Then, it initializes a MQTT object using the network interface (esp, ethernet) you are using:

# Initialize MQTT interface with the esp interface MQTT.set_socket(socket, esp)

Once a WiFi network connection has been established, the code sets up a new MiniMQTT client instance

client = MQTT(broker = secrets['broker'], username = secrets['user'], password = secrets['pass'])

Then, the code attaches callback handler methods to the client.

# Connect callback handlers to client client.on_connect = connect client.on_disconnect = disconnect client.on_subscribe = subscribe client.on_unsubscribe = unsubscribe client.on_publish = publish

MiniMQTT Callback Methods

We're going to stop here to explain the utility and operation of the callback methods which are an important part of building programs with MiniMQTT.

Further up in the code, there are methods named connect() , publish() , subscribe() , unsubscribe() and

disconnect() .

def connect(client, userdata, flags, rc): # This function will be called when the client is connected # successfully to the broker. print('Connected to MQTT Broker!') print('Flags: {0}\n RC: {1}'.format(flags, rc))

def disconnect(client, userdata, rc): # This method is called when the client disconnects # from the broker. print('Disconnected from MQTT Broker!')

def subscribe(client, userdata, topic, granted_qos): # This method is called when the client subscribes to a new feed. print('Subscribed to {0} with QOS level {1}'.format(topic, granted_qos))

def unsubscribe(client, userdata, topic, pid): # This method is called when the client unsubscribes from a feed. print('Unsubscribed from {0} with PID {1}'.format(topic, pid))

def publish(client, userdata, topic, pid): # This method is called when the client publishes data to a feed. print('Published to {0} with PID {1}'.format(topic, pid))

Each of these methods is executed when a callback is successfully read back from a MQTT control packet sent by the client.

If you do not know what a MQTT Client or a MQTT Broker is , check out this

page (https://adafru.it/Fme).

This means that whenever MiniMQTT sends a CONNECT command to the MQTT broker , the broker should respond that it received it and send another packet back to MiniMQTT (called a

CONNACK

packet).

If MiniMQTT receives this CONNACK packet, it will execute the client's on_connect method . It'll raise an error if it did not connect successfully.

As an example, we'll set up a connect callback method named connect . This method will print the string,

Connected to MQTT Broker

, if it successfully connects to your MQTT broker.

def connect(client, userdata, flags, rc): print('Connected to MQTT Broker!')

Then, we'll

set

the client's on_connect property to the connect method.

client.on_connect = connect

To connect the MiniMQTT client to the broker, we'll run the following line:

client.connect()

When the client's connect() method runs, it sends a CONNECT command to the MQTT broker with information including the broker's address and waits for the CONNACK.

Once the CONNACK is received, MiniMQTT calls on_connect from "behind the scenes". Since connect is attached to on_connect , connect will execute and print out the following message:

Connected to MQTT Broker!

Ok - we now understand how the

connect

method callback works. The rest of the example calls more

functions which also execute similar callback methods.

First, the code attempts to connect to the MQTT broker you specified.

print('Attempting to connect to %s'%client.broker) client.connect()

If the CircuitPython board connects successfully, it'll run the connect method.

The code will next attempt to subscribe to a mqtt_topic you defined earlier in the code.

print('Subscribing to %s'%mqtt_topic) client.subscribe(mqtt_topic)

If the client successfully subscribes to the mqtt_topic , the subscribe method will execute.

Once the client successfully subscribes - it'll publish to the mqtt_topic .

print('Publishing to %s'%mqtt_topic) client.publish(mqtt_topic, 'Hello Broker!')

After publishing, your broker should display that it received a value from the client. In addition, the publish method should run.

Next, the client unsubscribes from the mqtt_topic and disconnects from the broker.

print('Unsubscribing from %s'%mqtt_topic) client.unsubscribe(mqtt_topic)

print('Disconnecting from %s'%client.broker) client.disconnect()

These two methods should call the unsubscribe and disconnect methods.

That's it! The next page will go over some of the more advanced features of this library.

Advanced MiniMQTT Usage MiniMQTT Loop

You should always use a loop when writing CircuitPython code which uses the MiniMQTT module . The loop methods check incoming and process outgoing mqtt messages along with keeping the network connection between your board and the MQTT broker alive .

MiniMQTT supports two different types of loops: loop and loop_forever .

loop

Calling loop creates a non-blocking network loop. You can create new code below the call to loop , and it'll be executed. This type of loop should be run frequently to avoid disconnecting from the MQTT server.

The loop method also does not handle network hardware (WiFi) or MQTT broker disconnection . You'll need to handle that yourself.

Here's an example of using a non-blocking loop.

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT

import time import board import busio from digitalio import DigitalInOut import neopixel from adafruit_esp32spi import adafruit_esp32spi from adafruit_esp32spi import adafruit_esp32spi_wifimanager import adafruit_esp32spi.adafruit_esp32spi_socket as socket

import adafruit_minimqtt.adafruit_minimqtt as MQTT

### WiFi ###

# Get wifi details and more from a secrets.py file try: from secrets import secrets except ImportError: print("WiFi secrets are kept in secrets.py, please add them there!") raise

# If you are using a board with pre-defined ESP32 Pins: esp32_cs = DigitalInOut(board.ESP_CS) esp32_ready = DigitalInOut(board.ESP_BUSY) esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an externally connected ESP32: # esp32_cs = DigitalInOut(board.D9) # esp32_ready = DigitalInOut(board.D10) # esp32_reset = DigitalInOut(board.D5)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO) esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset) """Use below for Most Boards""" status_light = neopixel.NeoPixel( board.NEOPIXEL, 1, brightness=0.2 ) # Uncomment for Most Boards """Uncomment below for ItsyBitsy M4"""

# status_light = dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1, brightness=0.2) # Uncomment below for an externally defined RGB LED # import adafruit_rgbled # from adafruit_esp32spi import PWMOut # RED_LED = PWMOut.PWMOut(esp, 26) # GREEN_LED = PWMOut.PWMOut(esp, 27) # BLUE_LED = PWMOut.PWMOut(esp, 25) # status_light = adafruit_rgbled.RGBLED(RED_LED, BLUE_LED, GREEN_LED) wifi = adafruit_esp32spi_wifimanager.ESPSPI_WiFiManager(esp, secrets, status_light)

### Adafruit IO Setup ###

# Setup a feed named `testfeed` for publishing. default_topic = secrets["user"] + "/feeds/testfeed"

### Code ### # Define callback methods which are called when events occur # pylint: disable=unused-argument, redefined-outer-name def connected(client, userdata, flags, rc): # This function will be called when the client is connected # successfully to the broker. print("Connected to MQTT broker! Listening for topic changes on %s" % default_topic) # Subscribe to all changes on the default_topic feed. client.subscribe(default_topic)

def disconnected(client, userdata, rc): # This method is called when the client is disconnected print("Disconnected from MQTT Broker!")

def message(client, topic, message): """Method callled when a client's subscribed feed has a new value. :param str topic: The topic of the feed with a new value. :param str message: The new value """ print("New message on topic {0}: {1}".format(topic, message))

# Connect to WiFi print("Connecting to WiFi...") wifi.connect() print("Connected!")

# Initialize MQTT interface with the esp interface MQTT.set_socket(socket, esp)

# Set up a MiniMQTT Client mqtt_client = MQTT.MQTT( broker=secrets["broker"], username=secrets["user"], password=secrets["pass"] )

# Setup the callback methods above mqtt_client.on_connect = connected mqtt_client.on_disconnect = disconnected mqtt_client.on_message = message

# Connect the client to the MQTT broker. mqtt_client.connect()

photocell_val = 0 while True:

# Poll the message queue mqtt_client.loop()

# Send a new message print("Sending photocell value: %d" % photocell_val) mqtt_client.publish(default_topic, photocell_val) photocell_val += 1 time.sleep(0.5)

Here's an example of using a loop with a network interface. In this example, we use the loop to reset the network interface ( wifi.reset ) and reconnect the socket to the MQTT broker ( mqtt_client.reconnect )

# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries # SPDX-License-Identifier: MIT

import time import board import busio from digitalio import DigitalInOut import neopixel from adafruit_esp32spi import adafruit_esp32spi from adafruit_esp32spi import adafruit_esp32spi_wifimanager import adafruit_esp32spi.adafruit_esp32spi_socket as socket

import adafruit_minimqtt.adafruit_minimqtt as MQTT

### WiFi ###

# Get wifi details and more from a secrets.py file try: from secrets import secrets except ImportError: print("WiFi secrets are kept in secrets.py, please add them there!") raise

# If you are using a board with pre-defined ESP32 Pins: esp32_cs = DigitalInOut(board.ESP_CS) esp32_ready = DigitalInOut(board.ESP_BUSY) esp32_reset = DigitalInOut(board.ESP_RESET)

# If you have an externally connected ESP32: # esp32_cs = DigitalInOut(board.D9) # esp32_ready = DigitalInOut(board.D10) # esp32_reset = DigitalInOut(board.D5)

spi = busio.SPI(board.SCK, board.MOSI, board.MISO) esp = adafruit_esp32spi.ESP_SPIcontrol(spi, esp32_cs, esp32_ready, esp32_reset) """Use below for Most Boards""" status_light = neopixel.NeoPixel( board.NEOPIXEL, 1, brightness=0.2 ) # Uncomment for Most Boards """Uncomment below for ItsyBitsy M4""" # status_light = dotstar.DotStar(board.APA102_SCK, board.APA102_MOSI, 1, brightness=0.2) # Uncomment below for an externally defined RGB LED # import adafruit_rgbled # from adafruit_esp32spi import PWMOut # RED_LED = PWMOut.PWMOut(esp, 26) # GREEN_LED = PWMOut.PWMOut(esp, 27) # BLUE_LED = PWMOut.PWMOut(esp, 25) # status_light = adafruit_rgbled.RGBLED(RED_LED, BLUE_LED, GREEN_LED) wifi = adafruit_esp32spi_wifimanager.ESPSPI_WiFiManager(esp, secrets, status_light)

### Adafruit IO Setup ###

# Setup a feed named `testfeed` for publishing. default_topic = secrets["user"] + "/feeds/testfeed"

### Code ###

# Define callback methods which are called when events occur # pylint: disable=unused-argument, redefined-outer-name def connected(client, userdata, flags, rc): # This function will be called when the client is connected # successfully to the broker. print("Connected to MQTT broker! Listening for topic changes on %s" % default_topic) # Subscribe to all changes on the default_topic feed. client.subscribe(default_topic)

def disconnected(client, userdata, rc): # This method is called when the client is disconnected print("Disconnected from MQTT Broker!")

def message(client, topic, message): """Method callled when a client's subscribed feed has a new value. :param str topic: The topic of the feed with a new value. :param str message: The new value """ print("New message on topic {0}: {1}".format(topic, message))

# Connect to WiFi print("Connecting to WiFi...") wifi.connect() print("Connected!")

# Initialize MQTT interface with the esp interface MQTT.set_socket(socket, esp)

# Set up a MiniMQTT Client mqtt_client = MQTT.MQTT( broker=secrets["broker"], username=secrets["user"], password=secrets["pass"] )

# Setup the callback methods above mqtt_client.on_connect = connected mqtt_client.on_disconnect = disconnected mqtt_client.on_message = message

# Connect the client to the MQTT broker. print("Connecting to MQTT broker...") mqtt_client.connect()

# Start a blocking message loop... # NOTE: NO code below this loop will execute # NOTE: Network reconnection is handled within this loop while True: try: mqtt_client.loop() except (ValueError, RuntimeError) as e: print("Failed to get data, retrying\n", e) wifi.reset() mqtt_client.reconnect()

continue time.sleep(1)

MiniMQTT Client Identifier

By default, MiniMQTT will generate a unique, randomly generated client identifier based off the CircuitPython device's microcontroller's UUID and a random number. The broker will see a client named something like

cpy-3123

If you'd like to set a custom client_id (what the broker sees the CircuitPython device as), you can provide a string. Do make sure the client_id 's you create are unique, or your broker will disconnect them.

client = MQTT(broker = secrets['broker'],

username = secrets['user'],

password = secrets['pass'],

client_id = 'brentspyportal')

MiniMQTT Logging

MiniMQTT uses the CircuitPython logger module (https://adafru.it/Ehw) for printing different types of errors, depending on the priority the logger was set to.

To attach a logger to a MiniMQTT client, simply

client = MQTT.MQTT(broker = secrets['broker'],

username = secrets['user'],

password = secrets['pass'],

log = True)

Then, you will need to add another line setting the logger's level. While the logger is initialized to the INFO level by default, you may want to see more information about your current MQTT session.

To set the logger to a higher priority logging level , like DEBUG, add the following line

after

the MQTT

client has been initialized:

client.set_logger_level(DEBUG)

MiniMQTT Last Will and Testament

MiniMQTT supports setting publishing a message to a specific topic when your MQTT client disconnects.

For more information about MQTT's Last Will - check this guide (https://adafru.it/Fmf).

To use the last will - specify the topic you'd like to publish to and provide it with a message to publish when the client disconnects.

client.set_will(topic='device/status/', message='Goodbye!')

This method must be called before the connect method . The last will and testament also must be allowed by your MQTT Broker - Adafruit IO does

not

support this feature.

Adafruit MQTT in CircuitPython Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual