.Netwroking & communications.

Networking & Communication in Embedded Systems

Networking and communication allow embedded devices to share data with sensors, displays, and other microcontrollers. Instead of working alone, devices can communicate over protocols like I²C, SPI, UART, and CAN to build more complex systems.

I²C Communication: SDA & SCL Pins

I²C (Inter-Integrated Circuit) is a two-wire communication protocol widely used in embedded programming. It uses:

• SDA (Serial Data) – Transfers data between devices
• SCL (Serial Clock) – Synchronizes communication using a clock signal

Multiple devices can share the same SDA and SCL lines, each with a unique address. This makes I²C efficient for connecting many peripherals using only two pins.

Applications

• Connecting sensors (temperature, IMU, distance sensors)
• Display modules (OLED, LCD)
• Real-Time Clock (RTC) modules
• Communication between multiple microcontrollers
• IO expanders to increase GPIO pins

For this weeks exploration i tried a couple variations

Xiao RP2040 - ESP wroom 32 via I2C

Xiao rp2040 - Arduino uno r3 via I2C

ESP WROOM 32 - ESP WROOM 32 via WIFI

RP2040 - ESP WROOM 32

For I2C connection it is crucial to connect both the boards GND together

Never use adapters like these, they are horrible at data transfers and its impossible to tell if its faulty code, improper wiring or adapter issues

Remember debugging needs as little variables as you can possibly have adapters like these increase the variables.

Here is the code to be uploaded to master

  void setup() {
  Serial.begin(115200);
}

void loop() {
  int minVal = 4095, maxVal = 0;
  
  // Sample for 200ms
  unsigned long start = millis();
  while (millis() - start < 200) {
    int val = analogRead(A0);
    if (val < minVal) minVal = val;
    if (val > maxVal) maxVal = val;
  }

  Serial.print("Min: "); Serial.print(minVal);
  Serial.print("  Max: "); Serial.print(maxVal);
  Serial.print("  Range: "); Serial.println(maxVal - minVal);
  delay(100);
}
  

.ESP to Laptop.

Connecting esp to lapyop via wifi using espnow

For my final project I also needed an external device to send data, I decided to explore that here.

This is crucial to increase the range.

#include 
#include 
#include 

// Your WiFi credentials
const char* ssid = "Scarlett";
const char* password = "Scarlett$123";

#define LED_PIN D0
#define NUM_LEDS 42

Adafruit_NeoPixel strip(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);
WebSocketsServer webSocket = WebSocketsServer(81);

void onWebSocketEvent(uint8_t client, WStype_t type, uint8_t* payload, size_t length) {
  if (type == WStype_BIN && length == NUM_LEDS * 3) {
    // Received 126 bytes — one RGB value per LED
    for (int i = 0; i < NUM_LEDS; i++) {
      uint8_t r = payload[i * 3];
      uint8_t g = payload[i * 3 + 1];
      uint8_t b = payload[i * 3 + 2];
      strip.setPixelColor(i, strip.Color(r, g, b));
    }
    strip.show();
  }
}

Upload this code on the baord.

replace the wifi credentials IN CODE to your wifi ssid and password.

Networking redo

For the redo i decided to do a basic exploration to establish connections between 2 boards

ESP-32-S3 & ESP 8266

I am using the same board as my final project, the gerber files and more can be found in the download section here

I wired the POT meter again just as in Input devices

Basic steps to Network the two boards-

1. retrive mac address from slave board after flashing code to th eboard

2. print the retreived mac address to the master board code and flash with desired function.

3. prep receiver code.

4. flash both boards with respective codes wire components and power both boards.

1.

#include 

void setup() {
  Serial.begin(115200);
  delay(500);
  Serial.println();
  Serial.print("ESP8266 MAC Address: ");
  Serial.println(WiFi.macAddress());
}

void loop() {}

Flash this code to the ESP8266 to retrive mac address. Open terminal and sync bnaud lengths and youll recieve the mac address

#include 

void setup() {
  Serial.begin(115200);
  delay(500);
  WiFi.mode(WIFI_STA);
  Serial.println();
  Serial.print("ESP32-S3 MAC Address: ");
  Serial.println(WiFi.macAddress());
}

void loop() {}

Same fucntion code for the s3 in case you need bi-directinal networking.

wire the board as such if you are following along.

2.

#include 
#include 

// ← Replace with YOUR ESP8266's MAC address from Step 1
uint8_t receiverMac[] = {};

#define POT_PIN  1   // D0 on XIAO ESP32-S3 = GPIO1

typedef struct {
  int potValue;
} DataPacket;

DataPacket packet;

void onSent(const uint8_t *mac, esp_now_send_status_t status) {
  Serial.print("Send status: ");
  Serial.println(status == ESP_NOW_SEND_SUCCESS ? "OK" : "FAIL");
}

void setup() {
  Serial.begin(115200);
  WiFi.mode(WIFI_STA);

  if (esp_now_init() != ESP_OK) {
    Serial.println("ESP-NOW init failed");
    return;
  }

  esp_now_register_send_cb(onSent);

  esp_now_peer_info_t peer = {};
  memcpy(peer.peer_addr, receiverMac, 6);
  peer.channel = 0;
  peer.encrypt = false;

  if (esp_now_add_peer(&peer) != ESP_OK) {
    Serial.println("Failed to add peer");
    return;
  }

  Serial.println("Sender ready");
}

void loop() {
  packet.potValue = analogRead(POT_PIN);  // 0–4095 (12-bit ADC)
  Serial.print("Pot value: ");
  Serial.println(packet.potValue);

  esp_now_send(receiverMac, (uint8_t *)&packet, sizeof(packet));

  delay(50);  // send ~20 times per second
}

paste the retrived esp 8266 mac address in the recieverMac[ ] array

once pasted upload this code to the ESP32-S3 the master board.

#include 
#include 

#define LED_PIN  5   // D1 on ESP8266 = GPIO5

typedef struct {
  int potValue;
} DataPacket;

void onReceive(uint8_t *mac, uint8_t *data, uint8_t len) {
  DataPacket packet;
  memcpy(&packet, data, sizeof(packet));

  // Map 0–4095 (ESP32 12-bit ADC) to 0–255 (8-bit PWM)
  int brightness = map(packet.potValue, 0, 4095, 0, 255);
  analogWrite(LED_PIN, brightness);

  Serial.print("Received: ");
  Serial.print(packet.potValue);
  Serial.print("  →  Brightness: ");
  Serial.println(brightness);
}

void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  WiFi.mode(WIFI_STA);
  WiFi.disconnect();

  if (esp_now_init() != 0) {
    Serial.println("ESP-NOW init failed");
    return;
  }

  esp_now_set_self_role(ESP_NOW_ROLE_SLAVE);
  esp_now_register_recv_cb(onReceive);

  Serial.println("Receiver ready");
  Serial.print("MAC: ");
  Serial.println(WiFi.macAddress());
}

void loop() {}

This is the reciever code, here the recived pot values (0 - 4095) is mapped to led brightness values (0 - 255)

I wired the esp8266 with a breadboard.

POWER BOTH BOARDS

final result

You can do the same with I2C as well with tx rx pins.