Your First Mesh Network

This tutorial builds on the Quick Start Guide to create a more comprehensive mesh network with multiple types of nodes and practical functionality.

Overview

We'll build a mesh network with three types of nodes:

Sensor Node - Collects and broadcasts environmental data
Controller Node - Receives sensor data and controls devices
Bridge Node - Connects mesh to external networks (WiFi/Internet)

Node 1: Sensor Node

This node simulates environmental sensors and broadcasts data to the mesh.

#include "painlessMesh.h"

#define MESH_PREFIX     "MyMeshNetwork"
#define MESH_PASSWORD   "somethingSneaky"
#define MESH_PORT       5555

Scheduler userScheduler;
painlessMesh mesh;

// Sensor simulation
float temperature = 22.5;
float humidity = 65.0;
uint32_t sensorId = 1001;

// Task to send sensor data every 30 seconds
Task taskSendSensor(30000, TASK_FOREVER, [](){
    // Simulate sensor readings with some variation
    temperature += random(-10, 10) / 10.0;
    humidity += random(-50, 50) / 10.0;
    
    // Keep values in reasonable ranges
    temperature = constrain(temperature, 15.0, 35.0);
    humidity = constrain(humidity, 30.0, 90.0);
    
    // Create JSON message
    String msg = "{";
    msg += "\"type\":\"sensor\",";
    msg += "\"nodeId\":" + String(mesh.getNodeId()) + ",";
    msg += "\"sensorId\":" + String(sensorId) + ",";
    msg += "\"temperature\":" + String(temperature, 1) + ",";
    msg += "\"humidity\":" + String(humidity, 1) + ",";
    msg += "\"timestamp\":" + String(mesh.getNodeTime());
    msg += "}";
    
    mesh.sendBroadcast(msg);
    Serial.printf("Sent sensor data: T=%.1f°C, H=%.1f%%\n", temperature, humidity);
});

void receivedCallback(uint32_t from, String &msg) {
    Serial.printf("Sensor Node: Received from %u: %s\n", from, msg.c_str());
    
    // Sensor nodes can respond to commands
    if (msg.indexOf("\"command\":\"read_sensor\"") > 0) {
        // Force immediate sensor reading
        taskSendSensor.forceNextIteration();
        Serial.println("Forced sensor reading requested");
    }
}

void newConnectionCallback(uint32_t nodeId) {
    Serial.printf("Sensor Node: New connection to %u\n", nodeId);
}

void changedConnectionCallback() {
    Serial.printf("Sensor Node: Changed connections. Nodes: %s\n", 
                  mesh.subConnectionJson().c_str());
}

void setup() {
    Serial.begin(115200);
    Serial.println("=== Sensor Node Starting ===");
    
    mesh.setDebugMsgTypes(ERROR | STARTUP | CONNECTION);
    mesh.init(MESH_PREFIX, MESH_PASSWORD, &userScheduler, MESH_PORT);
    mesh.onReceive(&receivedCallback);
    mesh.onNewConnection(&newConnectionCallback);
    mesh.onChangedConnections(&changedConnectionCallback);
    
    userScheduler.addTask(taskSendSensor);
    taskSendSensor.enable();
    
    Serial.printf("Sensor Node initialized. Node ID: %u\n", mesh.getNodeId());
}

void loop() {
    mesh.update();
}

Node 2: Controller Node

This node receives sensor data and can send commands to other nodes.

#include "painlessMesh.h"

#define MESH_PREFIX     "MyMeshNetwork"
#define MESH_PASSWORD   "somethingSneaky"
#define MESH_PORT       5555

Scheduler userScheduler;
painlessMesh mesh;

// Storage for sensor data
struct SensorData {
    uint32_t nodeId;
    uint32_t sensorId;
    float temperature;
    float humidity;
    uint32_t timestamp;
    bool valid;
};

SensorData sensors[10]; // Store data from up to 10 sensors
int sensorCount = 0;

// Task to request sensor data every 60 seconds
Task taskRequestData(60000, TASK_FOREVER, [](){
    String cmd = "{";
    cmd += "\"type\":\"command\",";
    cmd += "\"command\":\"read_sensor\",";
    cmd += "\"from\":" + String(mesh.getNodeId());
    cmd += "}";
    
    mesh.sendBroadcast(cmd);
    Serial.println("Requested sensor data from all nodes");
});

// Task to display collected data every 45 seconds
Task taskDisplayData(45000, TASK_FOREVER, [](){
    Serial.println("=== Collected Sensor Data ===");
    for (int i = 0; i < sensorCount; i++) {
        if (sensors[i].valid) {
            Serial.printf("Node %u (Sensor %u): T=%.1f°C, H=%.1f%%, Age=%u seconds\n",
                         sensors[i].nodeId, sensors[i].sensorId,
                         sensors[i].temperature, sensors[i].humidity,
                         (mesh.getNodeTime() - sensors[i].timestamp) / 1000000);
        }
    }
    Serial.println("============================");
});

void storeSensorData(uint32_t nodeId, uint32_t sensorId, float temp, float hum, uint32_t timestamp) {
    // Find existing entry or create new one
    int index = -1;
    for (int i = 0; i < sensorCount; i++) {
        if (sensors[i].nodeId == nodeId && sensors[i].sensorId == sensorId) {
            index = i;
            break;
        }
    }
    
    if (index == -1 && sensorCount < 10) {
        index = sensorCount++;
    }
    
    if (index != -1) {
        sensors[index].nodeId = nodeId;
        sensors[index].sensorId = sensorId;
        sensors[index].temperature = temp;
        sensors[index].humidity = hum;
        sensors[index].timestamp = timestamp;
        sensors[index].valid = true;
    }
}

void receivedCallback(uint32_t from, String &msg) {
    Serial.printf("Controller: Received from %u: %s\n", from, msg.c_str());
    
    // Parse sensor data
    if (msg.indexOf("\"type\":\"sensor\"") > 0) {
        // Simple JSON parsing (in production, use ArduinoJson library)
        int tempStart = msg.indexOf("\"temperature\":") + 14;
        int tempEnd = msg.indexOf(",", tempStart);
        float temperature = msg.substring(tempStart, tempEnd).toFloat();
        
        int humStart = msg.indexOf("\"humidity\":") + 11;
        int humEnd = msg.indexOf(",", humStart);
        float humidity = msg.substring(humStart, humEnd).toFloat();
        
        int sensorStart = msg.indexOf("\"sensorId\":") + 11;
        int sensorEnd = msg.indexOf(",", sensorStart);
        uint32_t sensorId = msg.substring(sensorStart, sensorEnd).toInt();
        
        int timeStart = msg.indexOf("\"timestamp\":") + 12;
        int timeEnd = msg.indexOf("}", timeStart);
        uint32_t timestamp = msg.substring(timeStart, timeEnd).toInt();
        
        storeSensorData(from, sensorId, temperature, humidity, timestamp);
        
        // Trigger actions based on sensor data
        if (temperature > 30.0) {
            Serial.println("WARNING: High temperature detected!");
            // Could send cooling command here
        }
        if (humidity > 80.0) {
            Serial.println("WARNING: High humidity detected!");
            // Could trigger ventilation here
        }
    }
}

void newConnectionCallback(uint32_t nodeId) {
    Serial.printf("Controller: New connection to %u\n", nodeId);
}

void changedConnectionCallback() {
    Serial.printf("Controller: Changed connections. Nodes: %s\n", 
                  mesh.subConnectionJson().c_str());
}

void setup() {
    Serial.begin(115200);
    Serial.println("=== Controller Node Starting ===");
    
    // Initialize sensor storage
    for (int i = 0; i < 10; i++) {
        sensors[i].valid = false;
    }
    
    mesh.setDebugMsgTypes(ERROR | STARTUP | CONNECTION);
    mesh.init(MESH_PREFIX, MESH_PASSWORD, &userScheduler, MESH_PORT);
    mesh.onReceive(&receivedCallback);
    mesh.onNewConnection(&newConnectionCallback);
    mesh.onChangedConnections(&changedConnectionCallback);
    
    userScheduler.addTask(taskRequestData);
    userScheduler.addTask(taskDisplayData);
    taskRequestData.enable();
    taskDisplayData.enable();
    
    Serial.printf("Controller Node initialized. Node ID: %u\n", mesh.getNodeId());
}

void loop() {
    mesh.update();
}

Node 3: Bridge Node

This node connects the mesh to WiFi/Internet for external connectivity.

#include "painlessMesh.h"
#include <WiFi.h>  // Use <ESP8266WiFi.h> for ESP8266

#define MESH_PREFIX     "MyMeshNetwork"
#define MESH_PASSWORD   "somethingSneaky"
#define MESH_PORT       5555

// External WiFi credentials
#define STATION_SSID     "YourHomeWiFi"
#define STATION_PASSWORD "YourWiFiPassword"

Scheduler userScheduler;
painlessMesh mesh;

// Task to report bridge status
Task taskBridgeStatus(30000, TASK_FOREVER, [](){
    String status = "{";
    status += "\"type\":\"bridge_status\",";
    status += "\"nodeId\":" + String(mesh.getNodeId()) + ",";
    status += "\"wifi_connected\":" + String(WiFi.status() == WL_CONNECTED ? "true" : "false") + ",";
    status += "\"wifi_rssi\":" + String(WiFi.RSSI()) + ",";
    status += "\"mesh_connections\":" + String(mesh.getNodeList().size()) + ",";
    status += "\"timestamp\":" + String(mesh.getNodeTime());
    status += "}";
    
    mesh.sendBroadcast(status);
    Serial.printf("Bridge Status: WiFi=%s, RSSI=%d, Mesh Nodes=%d\n",
                  WiFi.status() == WL_CONNECTED ? "Connected" : "Disconnected",
                  WiFi.RSSI(), mesh.getNodeList().size());
});

void receivedCallback(uint32_t from, String &msg) {
    Serial.printf("Bridge: Received from %u: %s\n", from, msg.c_str());
    
    // Forward sensor data to external server (example)
    if (msg.indexOf("\"type\":\"sensor\"") > 0 && WiFi.status() == WL_CONNECTED) {
        // Here you could forward to HTTP/MQTT/etc
        Serial.println("Would forward sensor data to external server");
    }
}

void newConnectionCallback(uint32_t nodeId) {
    Serial.printf("Bridge: New mesh connection to %u\n", nodeId);
}

void changedConnectionCallback() {
    Serial.printf("Bridge: Mesh topology changed. Nodes: %s\n", 
                  mesh.subConnectionJson().c_str());
}

void setup() {
    Serial.begin(115200);
    Serial.println("=== Bridge Node Starting ===");
    
    // Initialize mesh
    mesh.setDebugMsgTypes(ERROR | STARTUP | CONNECTION);
    mesh.init(MESH_PREFIX, MESH_PASSWORD, &userScheduler, MESH_PORT);
    mesh.onReceive(&receivedCallback);
    mesh.onNewConnection(&newConnectionCallback);
    mesh.onChangedConnections(&changedConnectionCallback);
    
    // Connect to external WiFi
    WiFi.begin(STATION_SSID, STATION_PASSWORD);
    Serial.printf("Connecting to WiFi: %s", STATION_SSID);
    
    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        Serial.print(".");
    }
    Serial.println();
    Serial.printf("WiFi connected! IP: %s\n", WiFi.localIP().toString().c_str());
    
    userScheduler.addTask(taskBridgeStatus);
    taskBridgeStatus.enable();
    
    Serial.printf("Bridge Node initialized. Node ID: %u\n", mesh.getNodeId());
}

void loop() {
    mesh.update();
}

Deployment Steps

Upload Sensor Node code to your first ESP32/ESP8266
Upload Controller Node code to your second device
Upload Bridge Node code to your third device (update WiFi credentials first!)
Power up all devices and open Serial Monitors to watch them connect
Observe the mesh in action:
- Sensor nodes broadcast environmental data
- Controller receives and processes sensor data
- Bridge provides external connectivity and status updates

What You'll See

Sensor Node Output

=== Sensor Node Starting ===
Sensor Node initialized. Node ID: 123456789
Sensor Node: New connection to 987654321
Sent sensor data: T=23.2°C, H=67.4%

Controller Node Output

=== Controller Node Starting ===
Controller Node initialized. Node ID: 987654321
Requested sensor data from all nodes
Controller: Received from 123456789: {"type":"sensor",...}
=== Collected Sensor Data ===
Node 123456789 (Sensor 1001): T=23.2°C, H=67.4%, Age=5 seconds

Bridge Node Output

=== Bridge Node Starting ===
Connecting to WiFi: YourHomeWiFi....
WiFi connected! IP: 192.168.1.100
Bridge Node initialized. Node ID: 555444333
Bridge Status: WiFi=Connected, RSSI=-45, Mesh Nodes=2

Key Features Demonstrated

Automatic Discovery: Nodes find each other automatically
Message Broadcasting: Sensor data reaches all interested nodes
JSON Communication: Structured data exchange
Command System: Controller can request data from sensors
External Connectivity: Bridge connects mesh to Internet
Self-Healing: Network continues working if nodes disconnect

Extending Your Mesh

Add More Sensors

Temperature/humidity sensors (DHT22)
Motion detectors (PIR)
Light sensors (photoresistor)
Soil moisture sensors

Add Actuators

LED strips for notifications
Servo motors for mechanical control
Relays for switching devices
Buzzers for alerts

External Integrations

MQTT broker connectivity
HTTP REST API calls
Home Assistant integration
Cloud database logging

Next Steps

Explore Custom Packages for type-safe messaging
Learn about Alteriom Extensions for pre-built sensor packages
Dive into Performance Configuration for optimization
Check out Troubleshooting if you encounter issues

Congratulations! You now have a working multi-node mesh network with real-world functionality.

getting started first mesh - Alteriom/painlessMesh GitHub Wiki

Your First Mesh Network

Overview

Node 1: Sensor Node

Node 2: Controller Node

Node 3: Bridge Node

Deployment Steps

What You'll See

Sensor Node Output

Controller Node Output

Bridge Node Output

Key Features Demonstrated

Extending Your Mesh

Add More Sensors

Add Actuators

External Integrations

Next Steps

⚠️ GitHub.com Fallback ⚠️

getting started first mesh - Alteriom/painlessMesh GitHub Wiki

Your First Mesh Network

Overview

Node 1: Sensor Node

Node 2: Controller Node

Node 3: Bridge Node

Deployment Steps

What You'll See

Sensor Node Output

Controller Node Output

Bridge Node Output

Key Features Demonstrated

Extending Your Mesh

Add More Sensors

Add Actuators

External Integrations

Next Steps

⚠️ **GitHub.com Fallback** ⚠️

⚠️ GitHub.com Fallback ⚠️