Week 11 - Networking and Communications

Group Assignment

• Send a message between two projects

Group work

Communication between two XIAO-ESP32C3 with wire UART connection

Assignment: Send a message between two projects. This section I and Xu have tried to send a message between two ESP32-C3 broad with UART connection. One board (Master) sends a message "ON" to the other board (Slave), which turns on an LED upon receiving the command.

Materials Needed

• 2× ESP32-C3 boards
• 1× LED
• 1× Resistor (220Ω recommended)
• Breadboard and jumper wires
• USB cables (for both boards)
• Arduino IDE

Circuit Setup

Slave Board (Receiving Side):

• Connect LED anode (longer leg) to GPIO 2 through a resistor
• Connect LED cathode to GND
  Wiring Between Xiao-ESP32 Boards:
• Master TX → Slave RX
• Master RX → Slave TX
• Master GND → Slave GND

Master Code (Sender - Board 1)

void setup() {
  Serial1.begin(9600, SERIAL_8N1, 20, 21); // RX=20, TX=21（D7, D6）
}

void loop() {
  Serial1.write('a'); // led on
  delay(4000);
  Serial1.write('b'); // led off
  delay(4000);
}

Slave Code (Receiver - Board 2)

#define led1 D2
// #define led2 9
// #define led3 10

void setup() {
  Serial.begin(115200);  
  Serial1.begin(9600, SERIAL_8N1, 20, 21);  // RX=20, TX=21（D7, D6）
  pinMode(led1, OUTPUT);
  digitalWrite(led1, LOW);
}

void loop() {
  while (Serial1.available()) {
    char c = Serial1.read();
    Serial.print("Received: ");
    Serial.println(c);

    if (c == 'a') {
      digitalWrite(led1, HIGH);
      Serial.println(c);
      delay(1000);
    } else {
      digitalWrite(led1, LOW);
      delay(1000);
    }

  }
}

Steps to Execute

• Connect the Boards: Use jumper wires to connect TX of Master to RX of Slave, and GND to GND.
• Upload Master Code: Connect Master board to PC and upload the master sketch.
• Upload Slave Code: Connect Slave board to PC and upload the slave sketch.
• Power the Boards: You can power both via USB or an external power source.
• Observe the Result: The LED on the Slave board will blink once every 2 seconds upon receiving the "ON" command from the Master.

Video 2025

The result is shown as video below.