11. Networking and communications¶

Group assignment:¶

• Send a message between two projects

To see our group assignment click here

Individual assignment:¶

• Design, build, and connect wired or wireless node(s) with network or bus addresses

MEGA 2560 ↔ ESP32¶

Interactive Training Project¶

Introduction¶

Welcome to this embedded systems communication project using:

• an Arduino Mega 2560;
• a custom ESP32 PCB;
• LEDs;
• and a push button.

In this training exercise, you will learn how to:

• establish UART communication between two microcontrollers;
• control LEDs remotely;
• create different lighting sequences;
• manage push button interactions;
• and understand serial communication basics.

1. Project Overview¶

The Arduino Mega acts as the master controller.

The ESP32 acts as the LED control module.

When the push button is pressed:

• the Mega sends a serial command;
• the ESP32 receives the command;
• and executes the corresponding LED animation.

2. Hardware Presentation¶

Arduino Mega 2560¶

The Mega is responsible for:

• reading the push button state;
• changing operating modes;
• sending UART commands to the ESP32.

ESP32 Custom PCB¶

The ESP32 board is responsible for:

• receiving UART data;
• controlling the LEDs;
• executing lighting sequences.

Your custom PCB includes:

• ESP32-WROOM module;
• integrated LEDs;
• power switch;
• UART connector;
• reset / control button.

3. Wiring the Push Button¶

Connection Table¶

How It Works¶

The button uses the internal pull-up resistor:

INPUT_PULLUP

This means:

4. UART Communication¶

Serial Link Between Boards¶

¶

Important UART Rule¶

The serial lines must always be crossed:

TX → RX
RX → TX

Why Use UART?¶

UART communication allows:

• microcontroller-to-microcontroller communication;
• sensor sharing;
• remote LED control;
• data exchange;
• wireless gateway creation.

5. ESP32 LED Configuration¶

LED Assignment¶

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6. Sequence Logic¶

Mode 1 — Chained Sequence¶

Visual Effect¶

LED1 → LED2 → LED3

• sequential timing;
• digital output control;
• delay management.

Mode 2 — Synchronized Blink¶

Visual Effect¶

LED1 + LED2 + LED3
ON / OFF / ON / OFF

This allowed us to do:

• simultaneous GPIO control;
• repetitive loops;
• synchronized timing.

7. Operating Principle¶

8. Arduino Mega Program¶

Role of the Program¶

The Mega program:

• detects button presses;
• changes operating modes;
• sends UART commands to the ESP32.

Arduino Mega Code¶

const int bouton = 2;

bool mode = false;

unsigned long lastPress = 0;

void setup() {

  pinMode(bouton, INPUT_PULLUP);

  Serial1.begin(9600);
}

void loop() {

  if(digitalRead(bouton) == LOW &&
     millis() - lastPress > 300) {

    mode = !mode;

    if(mode) {

      Serial1.write('B');
    }
    else {

      Serial1.write('A');
    }

    lastPress = millis();
  }
}

9. Understanding the Mega Code¶

Anti-Bounce Protection¶

millis() - lastPress > 300

This prevents:

• multiple unwanted detections;
• noisy button transitions.

Mode Switching¶

mode = !mode;

This instruction toggles between:

• mode 1;
• and mode 2.

10. ESP32 Program¶

Role of the ESP32¶

The ESP32:

• waits for UART commands;
• decodes received characters;
• executes LED sequences.

ESP32 Code¶

const int led1 = 16;
const int led2 = 17;
const int led3 = 26;

void setup() {

  Serial.begin(9600);

  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
}

void sequenceChaine() {

  digitalWrite(led1, HIGH);
  delay(200);
  digitalWrite(led1, LOW);

  digitalWrite(led2, HIGH);
  delay(200);
  digitalWrite(led2, LOW);

  digitalWrite(led3, HIGH);
  delay(200);
  digitalWrite(led3, LOW);
}

void sequenceBlink() {

  for(int i = 0; i < 5; i++) {

    digitalWrite(led1, HIGH);
    digitalWrite(led2, HIGH);
    digitalWrite(led3, HIGH);

    delay(300);

    digitalWrite(led1, LOW);
    digitalWrite(led2, LOW);
    digitalWrite(led3, LOW);

    delay(300);
  }
}

void loop() {

  if(Serial.available()) {

    char cmd = Serial.read();

    if(cmd == 'A') {

      sequenceChaine();
    }

    if(cmd == 'B') {

      sequenceBlink();
    }
  }
}

11. Upload Procedure¶

Before Uploading¶

Disconnect:

• TX;
• RX.

This prevents UART conflicts during programming.

Upload Sequence¶

1. Disconnect TX/RX
2. Upload the code
3. Reconnect TX/RX
4. Reset the ESP32 if necessary

12. Power Supply¶

Arduino Mega¶

ESP32¶

13. Important Electrical Rule¶

The GND must always be shared between both boards.

Without a common ground:

• UART communication becomes unstable;
• data corruption may occur.

14. Training Objectives¶

After completing this project, you should understand:

• UART serial communication;
• GPIO control;
• push button handling;
• timing and delays;
• multi-board architecture;
• master/slave communication systems.

15. Possible Improvements¶

You can later add:

• OLED display;
• DHT11 sensor;
• Wi-Fi communication;
• Home Assistant integration;
• Bluetooth control;
• relay modules;
• joystick navigation;
• MQTT communication.

16. Final System Architecture¶

Push Button
     ↓
Arduino Mega 2560
     ↓ UART
Custom ESP32 PCB
     ↓
LED Sequences

Individual assignment:¶

• Design, build, and connect wired or wireless node(s) with network or bus addresses