IoT with Raspberry PI Pico W (C++)

The goals for this section:

• Raspberry PI Pico Setup

• SDK and Code Deployment

• MQTT Broker Service

• First Pico-W Thing

Setting up the Pico-W with header pins and the SDK.

A reminder of the two approaches available to copy binary code onto the Pico-W.

The course code repository is on GitHub. Its structure and how to download it.

We will require an MQTT Broker to get IoT devices to connect. Introducing the concept of a broker.

How to install a local MQTT Broker on a Raspberry PI 4.

How to use the Flespi as a cloud-hosted MQTT BRoker.

A first example IoT Thing built out to run against the broker and control an LED.

Section Summary and Resources.

Goals of this section are to explain the features of MQTT and the Software Stack this course will build.

MQTT originated in 1999 and is now a common IoT device protocol. This lecture looks at the features of MQTT.

To operate MQTT on the Pico-W we require a software stack that will handle the messaging. Ontop of this stack can sit our application. This lecture outlines the stack we will spend the rest of the course building.

Section summary and resources.

This section is all about establishing a connection:

• Wifi Connection

• Socket Transport

• MQTT Connection or Session

Connecting Raspberry PI Pico to a WIFI SSID.

Establishing an MQTT session using coreMQTT-Agent

Section Summary and Resources.

The goals of this section are to be able to publish.

• MQTT Topic Space that we will publish into

• Listen in Python to the Pico-W publish a message

• Publish using coreMQTT-Agent:

• Lifecycle Message when Pico-W connects

• LED Status

MQTT publishes messages to topics. Topics form a hierarchical space.

To show we have published we need a listener. For this section, we will listen from a Python test script.

MQTT does not produce any message on a device first connecting to the broker.  In this lecture we add to the framework to publish a message each time we connect.

We attach a switch and LED to the Pico-W so that pushing the switch changes the state of the LED (on to off). Then publish the state of the LED over MQTT.

Section Summary and Resources.

This section is all about subscribing and receiving messages on the Pico-W.

• Publish and control from Python

• Look at coreMQTT-Agent Subscribe Feature

• Explore group of Pico-W devices communicating

We need to be able to send messages to our Pico-W IoT device. We will once again use Python to provide these test scripts.

To enable subscription we will need to extend our framework by:

• Wrapping the  Subscribe Function

• Handle Subscription Call-back

• Handle Incoming Data Call-back

This lecture explores the design for extending our framework before we get into an example in the next lecture.

This example extends are latched LED device to be remotely controllable over MQTT.

In this example, we will use two Pico-W both operating as latched LED lights. We will make the switch on either device to control both devices at once.

Section summary and resources.

This section will look at the concepts of security for MQTT.

• Transport

• Authentication

• MQTT Topic Space Authorization

• Audit Logging

Securing the transport layer.

Building a TLS transport layer using WolfSSL and testing with HTTP GET.

Updating the IoT framework to secure the MQTT session over a TLS socket.

Importance of authentication to identify the client device.

Authorising access to the topic space for the clients.

Audit log to identify unusual behaviour for debugging and security assessment.

Section Summary

This section explores how the state of our device is actually a generalised problem and can have a general interface.

• State Problem

• Digital Twin Concept

• State for Pico-W

This lecture generalises the concept of state for our sensor or controller devices. How a digital twin service might help us manage these devices.

This section explores one way of extending our framework to manage the state in a general way. You could do this in lots of other ways.

Section Summary and Resources.

Congratulations on completing the course. Please leave a positive review on Udemy and get in touch to tell me how you are putting the knowledge to use.