Networking and Communication¶

In Week11 project I work on to demonstrates direct node-to-node wireless communication using two ESP32 microcontrollers. The system uses the ESP-NOW protocol, allowing communication without internet or external servers.

SSTM¶

SSTM

Assignments

Group Assignment¶

Send a message between two projects

In the group assignment, two independent projects will communicate by exchanging messages using a selected communication protocol (such as ESP-NOW, I2C, or UART). Each project will act as a node and demonstrate successful data transmission between systems. We are work on MQTTs things.

Individual Assignment¶

I am using ESP WROOM 32D to design, build, and connect wireless node(s) with network MAC addresses.

Two nodes were developed:

Node A (Sender) → Reads input from sensors
Node B (Receiver) → Controls output devices

System Architecture¶

System Architecture

Software¶

On Arduino IDE install the ESP library from the espressif (critical)
Arduino IDE will be used to generate the MAC address of the Node B and write in the code by save it somewhere for code t be write to Node A

ESP-NOW Project — Initial IDE Setup¶

1. Install Arduino IDE.¶

not installed befor/ if required

Download and install Arduino IDE
Open the software after installation

2. Install ESP32 Board Package¶

Go to File → Preferences
In “Additional Board Manager URLs”, paste:

[ESP-32 espressif download](https://dl.espressif.com/dl/package_esp32_index.json) 3. Go to Tools → Board → Boards Manager 4. Search for:

esp32 5. Install ESP32 by Espressif Systems

3. Select ESP32 Board¶

Go to Tools → Board → ESP32 Arduino → ESP32 Dev Module

4. Select Port¶

Go to Tools → Port
Select the port connected to your ESP32

5. Required Libraries¶

These are included automatically with ESP32:

WiFi.h
esp_now.h

No manual installation is required.

ESP espressif setup

6. Find MAC Address¶

Upload the following code to each ESP32:

#include <WiFi.h>

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

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

MAC ADDRESS

void loop() {}

Open Serial Monitor and note the MAC address:

Example: 7C:9E:BD:F6:5F:D4

Convert it to ESP-NOW format:

uint8_t address[] = {0x7C, 0x9E, 0xBD, 0xF6, 0x5F, 0xD4};

7. Define Node Roles¶

Node	Role
Node A	Sender
Node B	Receiver

8. Set WiFi Mode (Both Nodes)¶

WiFi.mode(WIFI_STA);

9. Initialize ESP-NOW¶

esp_now_init();

10. Add Peer (Sender Only)¶

esp_now_peer_info_t peerInfo = {};
memcpy(peerInfo.peer_addr, receiverAddress, 6);
esp_now_add_peer(&peerInfo);

11. Register Receive Callback (Receiver Only)¶

esp_now_register_recv_cb(onReceive);

12. System Overview¶

Node A sends data using ESP-NOW
Node B receives data and controls output devices
Communication is direct (no internet or router required)

13. Common Errors and Fixes¶

Problem	Cause	Solution
WiFi.h not found	Wrong board selected	Select ESP32 board
No communication	Incorrect MAC address	Verify MAC
Send failed	Peer not added	Add peer correctly
No data received	Callback missing	Register receive callback

14. Ready for Implementation¶

After completing setup:

Upload sender code to Node A
Upload receiver code to Node B
Power both boards
Test communication using Serial Monitor

Succesfull ESP Communication¶

succesfull_esp_communication

This completes the initial setup for ESP-NOW communication. When ever I face Error … I copied and debug with AI… with prompt like ” could you correct the error in the following code”

error debug

Hardware Components¶

Node A (Sender)¶

MCU: ESP32 WROOM 32D
Input device: Flame Sensor KY-026
Input device: Rotary Encoder KY-040

Node B (Receiver)¶

MCU: ESP32 WROOM 32D
Out put device: RGB LED KY-016 (with resistors)

Connection Details¶

Node A (Sender)¶

Flame Sensor¶

Pin	Connection
VCC	3.3V
GND	GND
DO	GPIO 34

Rotary Encoder¶

Pin	Connection
CLK	GPIO 25
DT	GPIO 26
SW	GPIO 27 (optional)
VCC	3.3V
GND	GND

Setup and correction

Node B (Receiver)¶

RGB LED (Common Cathode)¶

Pin	Connection
Red	GPIO 14
Green	GPIO 12
Blue	GPIO 13
GND	GND

Note: Each color pin uses a 220Ω resistor but my module have already installed resistor.

Network Addressing¶

Node	MAC Address
Node B (Receiver)	7C:9E:BD:F6:5F:D4

Node A sends data directly to this address using ESP-NOW.

Communication Method¶

Feature	Description
Protocol	ESP-NOW
Type	Wireless
Internet Required	No
Communication	Direct device-to-device

System Operation¶

Flame sensor detects fire and sends a signal
Rotary encoder changes value and sends control data
Node A transmits data via ESP-NOW
Node B receives data and reacts:
Flame detected → Red LED ON
Rotary changes → LED color changes

Flowchart¶

Node A (Sender)¶

ESP-NOW Flame Detection and Rotary encoder Workflow general description¶

ESP-NOW

This is described below as workflow illustrates the logical sequence for an ESP-NOW based flame detection system. The system continuously listens at Node A for data, evaluates flame detection, and responds with LED control at Node B.

Node A (Sender)¶

A. Workflow Steps for Flame sensor¶

1. Start¶

System initialization begins.

2. Initialize ESP-NOW¶

Configure ESP-NOW communication protocol
Set up MAC Address

3. Wait for Data¶

Device enters listening mode
Await incoming sensor data packets

4. Receive Data¶

Capture transmitted data from flame sensor
Parse and validate data integrity

5. Decision: Flame Detected?¶

YES → Turn RED LED ON
Immediate visual alert for flame presence
NO → Change RGB Color
Cycle or update RGB LED to indicate normal status

B. Workflow Steps for Rotary Encoder¶

ESP-NOW Rotary Encoder to RGB LED Workflow¶

Node A (Sender – Rotary Encoder)¶

1. Start¶

Begin system operation.

2. Initialize ESP32 + ESP-NOW¶

Configure ESP32 microcontroller
Set up ESP-NOW communication protocol

3. Read CLK and DT Pins¶

Monitor rotary encoder signals

4. Detect Rotation Direction¶

Determine clockwise or counterclockwise movement

5. Increase or Decrease Counter¶

Adjust counter value based on rotation

6. Limit Counter (0–255)¶

Ensure counter stays within valid range

7. Send Value via ESP-NOW¶

Transmit counter value to receiver node

8. Repeat Loop¶

Continue monitoring and sending values

Node B (Receiver – RGB LED)¶

1. Start¶

Begin system operation.

2. Initialize ESP32 + ESP-NOW¶

Configure ESP32 microcontroller
Set up ESP-NOW communication protocol

3. Wait for Data¶

Enter listening mode

4. Receive Rotary Value¶

Capture transmitted counter value

5. Calculate Mode = Value % 3¶

Compute mode based on modulo operation

6. Decision: LED Color¶

Mode == 0 → RED
Mode == 1 → GREEN
Mode == 2 → BLUE

7. Update LED Color¶

Change RGB LED to corresponding color

8. Wait for Next Data¶

Return to listening mode

rotary encoder

6. Repeat¶

Loop back to Wait for Data
Continuous monitoring cycle

Node B (Receiver)¶

Workflow Steps¶

1. Start¶

System initialization begins.

2. Initialize ESP-NOW¶

Configure ESP-NOW communication protocol
Set up peer-to-peer communication

3. Wait for Data¶

Device enters listening mode
Await incoming sensor data packets

4. Receive Data¶

Capture transmitted data from flame sensor
Parse and validate data integrity

5. Decision: Flame Detected?¶

YES → Turn RED LED ON
Immediate visual alert for flame presence
NO → Change RGB Color
Cycle or update RGB LED to indicate normal status

6. Repeat¶

Loop back to Wait for Data
Continuous monitoring cycle

Testing Results¶

Successful wireless communication between two ESP32 nodes
Real-time sensor data transmission
Immediate response on output device

Challenges and Solutions¶

Problem	Solution
ESP-NOW callback error	Updated to correct function format
No communication	Fixed MAC address and power
Unstable input	Used INPUT_PULLUP
Limited 3.3V pin	Shared using breadboard

Breadboard used for 3V3 pin extension

Learning Outcome¶

This project successfully demonstrates a direct wireless communication system between two embedded nodes using ESP32 and ESP-NOW using MAC address. I lean how to

Communication protocols (ESP-NOW)
Implementation of node-to-node communication
Integration of sensors and to remote outputs

Final work ESP-NOW-Video

Sources Code¶

Chat GPT used for Library and code generation

RECEIVER CODE¶

#include <WiFi.h>              //v WiFi library
#include <esp_now.h>           //v ESP-NOW library

int redPin = 14;               //v RED LED pin
int greenPin = 12;             //v GREEN LED pin
int bluePin = 13;              //v BLUE LED pin

typedef struct {               //v structure for received data
  int flame;
  int rotary;
} Data;

Data incoming;                 //v variable to store received data

//v NEW CALLBACK FORMAT (REQUIRED for ESP32 v3.x)
void onReceive(const esp_now_recv_info *info, const uint8_t *incomingData, int len) {

  memcpy(&incoming, incomingData, sizeof(incoming)); //v copy received data

  if (incoming.flame == 1) {        //v flame detected
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, LOW);
    digitalWrite(bluePin, LOW);
  } 
  else {                            //v no flame
    if (incoming.rotary % 3 == 0) {
      digitalWrite(redPin, HIGH);
      digitalWrite(greenPin, LOW);
      digitalWrite(bluePin, LOW);
    } 
    else if (incoming.rotary % 3 == 1) {
      digitalWrite(redPin, LOW);
      digitalWrite(greenPin, HIGH);
      digitalWrite(bluePin, LOW);
    } 
    else {
      digitalWrite(redPin, LOW);
      digitalWrite(greenPin, LOW);
      digitalWrite(bluePin, HIGH);
    }
  }
}

void setup() {
  Serial.begin(115200);         //v start serial

  pinMode(redPin, OUTPUT);      //v set RGB pins
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);

  WiFi.mode(WIFI_STA);          //v required mode

  if (esp_now_init() != ESP_OK) {   //v init ESP-NOW
    Serial.println("Error initializing ESP-NOW");
    return;
  }

  esp_now_register_recv_cb(onReceive); //v register callback
}

void loop() {
  //v nothing here
}

SENDER CODE¶

#include <WiFi.h>
#include <esp_now.h>

//v YOUR MAC ADDRESS USED CORRECTLY
uint8_t receiverAddress[] = {0x7C, 0x9E, 0xBD, 0xF6, 0x5F, 0xD4};

int flamePin = 34;
int clk = 25;
int dt = 26;

int lastStateCLK;
int counter = 0;

typedef struct {
  int flame;
  int rotary;
} Data;

Data data;

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

  pinMode(flamePin, INPUT);
  pinMode(clk, INPUT);
  pinMode(dt, INPUT);

  lastStateCLK = digitalRead(clk);

  WiFi.mode(WIFI_STA);

  if (esp_now_init() != ESP_OK) {
    Serial.println("Error");
    return;
  }

  esp_now_peer_info_t peerInfo = {}; //v IMPORTANT: initialize properly
  memcpy(peerInfo.peer_addr, receiverAddress, 6);
  peerInfo.channel = 0;
  peerInfo.encrypt = false;

  esp_now_add_peer(&peerInfo);
}

void loop() {
  int flameState = digitalRead(flamePin);

  int currentStateCLK = digitalRead(clk);

  if (currentStateCLK != lastStateCLK) {
    if (digitalRead(dt) != currentStateCLK) {
      counter++;
    } else {
      counter--;
    }
  }

  lastStateCLK = currentStateCLK;

  data.flame = flameState;
  data.rotary = counter;

  esp_now_send(receiverAddress, (uint8_t *) &data, sizeof(data));

  delay(200);
}