Creating IoT Applications Using Python 

Intro CEO @ AgileVision Software Engineer Studied at CNTU some time ago ;) 

Why Python? • Easy to learn • Easy to use • Lots of useful libraries • Go-to option for the ML/BigData • Loved by engineers and scientists (proven by Stackoverflow and TIOBE index) 

IoT Basics 

What is IoT? • A network of interconnected devices(things) • Each thing has its own compute module running a software and can be connected with multiple sensors or other devices • Things can be controlled or monitored remotely, not necessarily from the same physical network or location • Approach when the data is being preprocessed by a thing and then sent to the cloud/hub/control software is called edge computing. 

Typical IoT Setup Temperature Sensor Humidity Sensor Pump Controller Thing with three sensors, compute module and LTE/Wi-Fi module IoT Hub/Broker Client 

MQTT Protocol • Pub/sub based • Designed to be energy-efficient • Authentication and authorisation are required by the standard, but are implementation-specific • Transport level security is recommended by the standard. TLS is suggested 

TLS • Communication security protocol • Assumes there is a third-party authority which can be trusted to issue certificates (CA, certificate authority) • Can be used as a secure transport protocol for the MQTT 

IoT Broker • Server software used to connect MQTT clients • Provides authentication, authorization and secure encryption • Provides QoS and other features 

Meet ESP32 The queen of low-power devices 

ESP32 at a glance • Ultra Low-Power • Wi-Fi and Bluetooth Chip • Many supported interfaces and integrations • A ton of developer kits and tutorials! 

It’s coding time! Let’s get our hands dirty! 

We’ll need • Mosquitto MQTT broker • Python 3.7 • paho-mqtt client • ESP32-based devkit, we are using M5Stack 

Getting Mosquitto 1. Download a distribution from https://mosquitto.org/ 2. Launch as a service or as an application 

Checking everything up and running In one terminal window, execute the following command: mosquitto_sub -h localhost -t "testme" -v In another one, execute the following command mosquitto_pub -h localhost -t "testme" -m Hello This will send a “Hello” message to the “testme” topic. If everything was configured correctly, the window running the mosquitto_sub command will show the “Hello” message. 

Setting up M5Stack • Download Arduino IDE • Download and install UART driver • Check the connection 

Establishing Wi-Fi and MQTT connection void setup() { M5.begin(); WiFi.begin(ssid, pass); waitForWifi(); if (!mqttClient.connect( broker, port)) { // Infinite loop on failure while (1); } mqttClient.subscribe(topic); } 

Receiving messages if (messageSize) { M5.…setTextColor(0x51D); M5.…print( “Received a message with topic ‘"); M5.…print( mqttClient.messageTopic()); M5.…print("', length "); M5.…print(messageSize); M5.…print(" bytes:\n”); while( mqttClient.available()) { M5.…print( (char)mqttClient.read()); } } 

We’ve just seen some really awesome stuff! •Easy Wi-Fi configuration •MQTT connection using several lines of code •Device is not running any OS, by the way! 

Reading sensor data and sending it via MQTT float temperature = TH02.ReadTemperature(); mqttClient.beginMessage( tempTopic ); mqttClient.print( "Temperature is: “ ); mqttClient.print(temperature); mqttClient.endMessage(); 

More awesomeness! •Temperature sensor data readings •Publishing to another MQTT topic 

How it works ESP32 mosquitto_sub 

It’s Python time! We could use any other language, BTW 

Subscribing to a topic import paho.mqtt.client as mqtt from matplotlib import pyplot from matplotlib.animation import FuncAnimation client.on_message = on_message client.connect("test.mosquitto.org") client.subscribe("agilevision.io/ demo/temp0") def update(frame): global temperature client.loop() client.publish("agilevision.io/ demo", “GET"); x.append(datetime.now()) y.append(temperature) line.set_data(x, y) figure.gca().relim() figure.gca().autoscale_view() return line, 

Summary • IoT device and application are very broad terms. It can be whatever • MQTT is a really simple protocol • Arduino IDE can be a great tool for extremely fast prototyping, even for non-Arduino devices • Pick a right tool, not the “only true” tool for the task. No need to reinvent the wheel, especially for prototyping 

Questions?