11. Networking and Communications

For this week’s assignment we have worked as follows. Group assignment: - Send a message between two projects. - Document your work to the group work page and reflect on your individual page what you learned. Individual assignment: - Design, build and connect wired or wireless node(s) with network or bus addresses and a local interface.

Assignment Cheklist.

item	Activity	Status
task 1	Linked to the group assignment page and reflected on your individual page	IN PROGRESS
task 2	Documented your project and what you have learned from implementing networking and/or communication protocols.	IN PROGRESS
task 3	Explained the programming process(es) you used.	IN PROGRESS
task 4	Outlined problems and how you fixed them	IN PROGRESS
task 5	Included design files (or linked to where they are located if you are using a board you have designed and fabricated earlier) and original source code.	IN PROGRESS
task 6	Included a ‘hero shot’ of your network and/or communications setup	IN PROGRESS

Individual Assignment

The project presented below seeks to integrate the connection between an ESP32 DEV MODULE board and the well-known SEED XIAO RP2040 electronic board, using the data sending and receiving switches. We retrieve the data through a DHT11 humidity sensor, which will be reflected on an OLED display on the SEEED XIAO RP2040 board.

At first, the idea seems super simple; there have been some difficulties that I can describe as learning.

System design

For this task, we will use two different boards: - ESP32 DEV MODULE - SEEED XIAO RP2040

We will also use an input and output device to display the data. - Humidity Sensor - DHT11 - OLED Display

Assembly and samples

We base the connection issue on the specifications of our components and experience in this area.

Useful links

• Arduino IDE
• FEEDXIAO

Code Example

Code in ESP32

#include "DHT.h"

#define DHTPIN 4      
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);   
  // UART2: RX=16, TX=17
  Serial2.begin(9600, SERIAL_8N1, 16, 17);  
  dht.begin();
}

void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  if (isnan(h) || isnan(t)) {
    Serial.println("Error leyendo DHT11");
    delay(2000);
    return;
  }

  // Mostrar en monitor serial
  Serial.printf("Temperatura: %.1f °C, Humedad: %.1f %%\n", t, h);

  // Enviar al XIAO RP2040 por UART2
  Serial2.printf("%.1f,%.1f\n", t, h);

  delay(5000); 
}

Code on board seeed XIAO RP2040

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

String inputString = "";

void setup() {
  Serial1.begin(9600); 
  Serial.begin(115200); // Debug por USB

  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println("Error al iniciar OLED");
    while (true);
  }

  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println("Esperando datos...");
  display.display();
}

void loop() {
  while (Serial1.available()) {
    char c = Serial1.read();
    if (c == '\n') {
      processData(inputString);
      inputString = "";
    } else {
      inputString += c;
    }
  }
}

void processData(String data) {
  Serial.print("Recibido: ");
  Serial.println(data);

  int commaIndex = data.indexOf(',');
  if (commaIndex > 0) {
    String tempStr = data.substring(0, commaIndex);
    String humStr = data.substring(commaIndex + 1);

    float t = tempStr.toFloat();
    float h = humStr.toFloat();

    // Mostrar en OLED
    display.clearDisplay();
    display.setTextSize(2);
    display.setCursor(0, 0);
    display.print("T: ");
    display.print(t, 1);
    display.println("C");

    display.setCursor(0, 30);
    display.print("H: ");
    display.print(h, 0);
    display.println("%");

    display.display();
  }
}

Video

From Youtube

IN PROGRESS

## LEARNING, FINDING AND LESSONS

It is important to select the appropriate plates with the correct operating voltages so that we do not have connection or reading problems.

---

Last update: September 24, 2025