ESP32 Programming for the Internet of Things
ESP32 Programming for the Internet of Things
HTML, JavaScript, AJAX, MQTT and Websockets Solutions
About the Book
This book is not intended to comprehensively teach you the theory, but to give you practical and fully functional solutions, in the form of complete programs. Much of the theory is already known by some of you, or may be found in many other textbooks. But the programs presented here include a great effort and have many original solutions, following one of the basic paradigms of programming: "Keep i(o)t simple". And - the most important thing for such a book - all the programs have already been verified by third parties, in this case students from Hyperion University, who have provided a very valuable feedback.
About the Author
Table of Contents
Part I. IoT Communications using classic HTML / JavaScript technologies 8
1. General presentation of the book and hardware modules 9
1.1. General Objectives of the Work 9
1.2. Structure and method of using the paper 16
1.3. Hardware implementation. Coupling the inputs and outputs of the ESP32 module 17
1.4. Examples of boards with ESP microcontrollers 19
2. Developping ESP32 / ESP8266 IoT applications by using HTML / JavaScript 26
2.1. Arduino environment installation for ESP microcontrollers 26
2.2. Simple server using the ESP32 board 27
2.3. Assigning a static address for external access 30
2.4. Android Application using MIT App Inventor 37
3. The command of a GPIO port via WiFi 41
3.1. Creating a web page for submitting commands from a browser 41
3.2. Developing a Mobile Application for ESP32 Command Using MIT App Inventor 45
3.3. The use of a port different from 80 49
4. Analog and digital commands transmission to an ESP32 server from a MIT App Inventor application 54
4.1. General principles of analogue and digital transmissions 54
4.2. Performing digital-analog conversion via PWM in Arduino IDE 55
4.3. Analog command in MIT App Inventor 60
5. Bidirectional communication between client and server using MIT App Inventor 63
5.1. Requirements of bidirectional client-server communications 63
5.2. Periodically refreshing the web page through MIT App Inventor 65
5.3. Complete application for bidirectional communication in MIT App Inventor 68
5.4. The full ESP32 program for bidirectional communication with a MIT App Inventor client 71
6. Bidirectional transfer via web page. AJAX Technologies 73
6.1. Methods and Objects of AJAX Technology 73
6.2. Example of program for controlling a digital output with AJAX transmission 79
6.3. Example of program for controlling two digital outputs with AJAX transmission 84
7. Automatic refresh of the web page via AJAX 88
7.1. Principles of the automatic refresh 89
7.2. Example of program with automatic refresh via AJAX 90
7.3. Controlling of digital state and reading of digital and analog value via AJAX, with refresh 94
7.4. Program for controlling for two logic states and reading two logical values and one analog value, using AJAX, with refresh 100
8. Monitoring and command HTML/JS/CSS of analog values 108
8.1. Progressbar type elements designed through CSS 108
8.2. Example of program for monitoring four digital inputs and an analog one and control of two digital outputs. 111
9. Client-sever commands with receipt confirmation 115
9.1. Ensuring coherence in disrupted networks 115
9.2. Program with confirmation/retransmission of commands for two digital outputs and monitoring of four digital inputs and an analogue input 117
9.3. Slider-type analog control elements 125
10. ESP8266/32 programming using the ESP-IDF development environment and ECLIPSE 137
10.1. Installing the ESP-IDF development environment and setting the toolchain 138
10.2. Testing an example project 139
10.3. Installing and configuring Eclipse 142
Part II. IoT communications using MQTT technology 147
11. Using MQTT - Message Queuing Telemetry Transport technology 147
11.1. General presentation of MQTT technology 147
11.2. Installing and testing the PubSubClient library 154
12. Examples of applications dedicated to MQTT technology 158
12.1. Installing and using the HelloIoT application 158
12.2. Commands of some digital outputs of the ESP32 module 160
12.3. Analog command via PWM 165
12.4. Reading of digital and analog inputs 171
13. Programming MQTT communications using Node-Red development environment 182
13.1. Installing the Node-Red in Windows 183
13.2. Installing mosquitto in windows 186
13.3. Making MQTT communications via Node-Red 186
13.4. Programming in Node-Red 187
14. Controlling some outputs using Node-Red and Mosquitto on a Windows computer 188
14.1. Controlling digital outputs 188
14.2. Controlling an analog output using Node-Red 203
15. Monitoring some entries using Node-Red and Mosquitto on a Windows computer 207
15.1. Monitoring of analog inputs 207
15.2. Monitoring digital inputs 213
16. Using Node-Red and Mosquitto broker on Raspberry Pi 226
16.1. Installing Raspbian on Raspberry Pi 226
16.2. Install Mosquitto broker 227
16.4. Installing Node-Red Dashboard on Raspberry Pi 232
Part III. Internet communications using WebSockets technology 240
17. Using WebSockets technology on ESP32 240
17.1. General features of WebSockets technology 241
17.2. Transmission of a command to a digital output 244
17.3. Controlling three digital outputs 253
17.4. Analogic controlling of outputs, using the PWM technique 258
18. Monitoring of inputs through WebSockets 267
18.1. Monitoring of digital inputs through WebSockets 267
18.2. Monitoring an analog input via Websockets 275
18.3. Displaying an analog value through text and progress bar 279
18.4. Displaying of an analog value through text, progress bar and gauge 285
18.5. Displaying an analog value through text, progress bar, Gauge, and Line Chart 291
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