Step 1: The Hardware Build (Point-to-Point Wiring)
Since no breadboard is used, female-to-female jumper wires are connected directly between the pins of the ESP32 and the LoRa Ra-02 module.
- Data Lines (SPI Bus): * LoRa MOSI connects to ESP32 Pin GPIO 23
- LoRa MISO connects to ESP32 Pin GPIO 19
- LoRa SCK connects to ESP32 Pin GPIO 18
- LoRa NSS connects to ESP32 Pin GPIO 5
System Controls: * LoRa RST connects to ESP32 Pin GPIO 14
- LoRa DIO0 connects to ESP32 Pin GPIO 2
- Power Supply: * LoRa 3.3V connects to ESP32 Pin 3V3 (Main system power)
- LoRa GND connects to ESP32 Pin GND (Common ground)
- The SOS Trigger Button: * Button Terminal 1 connects to ESP32 Pin GPIO 4
Button Terminal 2 connects to ESP32 Pin GND
Step 2: The Software Setup
- Environment: Open the Arduino IDE software on your computer.
- Board Link: Install the ESP32 board library so the software recognizes your microcontrollers.
- Radio Drivers: Open the Library Manager, search for "LoRa" by Sandeep Mistry, and click install. This library allows the ESP32 to talk to the SX1278 radio chip.
Step 3: Coding the Two Nodes
You program the two identical hardware sets to play two different roles:
The Sender Node (The Beacon): You upload code to the first ESP32 that tells it to sit and wait for a button press or an offline web form submission. When triggered, it packages the location data and blasts it out instantly using ESP-NOW wireless protocol.
\\sender code #include <WiFi.h> #include <DNSServer.h> #include <WebServer.h> #include <esp_now.h> #include <esp_wifi.h> // --- Configuration --- // Your confirmed Receiver MAC Address uint8_t broadcastAddress[] = {0x3C, 0x8A, 0x1F, 0x5B, 0x02, 0x4C}; // Locked channel configuration alignment to match home router const int WIFI_CHANNEL = 12; const byte DNS_PORT = 53; const int BUTTON_PIN = 4; const int FLOOR_NUMBER = 2; DNSServer dnsServer; WebServer server(80); typedef struct struct_message { char msg[64]; int floor_num; } struct_message; struct_message myData; esp_now_peer_info_t peerInfo; const char HTML_CONTENT[] PROGMEM = R"rawliteral( <!DOCTYPE html> <html> <head> <meta name='viewport' content='width=device-width, initial-scale=1.0'> <title>EMERGENCY SOS SYSTEM</title> <style> body { font-family: Arial, sans-serif; text-align: center; background-color: #1a1a1a; color: white; padding: 20px; } .btn { background-color: #ff3333; color: white; border: none; padding: 20px 40px; font-size: 24px; font-weight: bold; border-radius: 10px; cursor: pointer; box-shadow: 0px 5px 15px rgba(255,51,51,0.4); width: 100%; max-width: 300px; } .btn:active { background-color: #cc0000; } input[type=text] { width: 100%; max-width: 280px; padding: 12px; margin: 20px 0; border-radius: 5px; border: none; font-size: 16px; color: black; } h1 { color: #ff3333; } </style> </head> <body> <h1>DISASTER RELIEF BEACON</h1> <p>Connected to Floor 2 Local Emergency Node. No network or internet required.</p> <form action='/submit' method='POST'> <input type='text' name='message' placeholder='Describe your emergency (e.g., Trapped, Injured)...' required><br><br> <input type='submit' class='btn' value='SEND SOS ALERT'> </form> </body> </html> )rawliteral"; void sendEmergencyPacket(const char* textAlert) { strncpy(myData.msg, textAlert, sizeof(myData.msg)); myData.floor_num = FLOOR_NUMBER; esp_err_t result = esp_now_send(broadcastAddress, (uint8_t *) &myData, sizeof(myData)); if (result == ESP_OK) { Serial.println("ESP-NOW Packet Dispatched Successfully."); } else { Serial.println("Error sending ESP-NOW packet."); } } void handleRoot() { server.send(200, "text/html", HTML_CONTENT); } void handleSubmit() { if (server.hasArg("message")) { String userMsg = server.arg("message"); Serial.print("Web SOS Triggered: "); Serial.println(userMsg); sendEmergencyPacket(userMsg.c_str()); server.send(200, "text/html", "<html><body style='background-color:#1a1a1a; color:white; font-family:Arial; text-align:center; padding-top:50px;'><h1>SOS SENT!</h1><p>Rescuers have been notified.</p></body></html>"); } } void setup() { Serial.begin(115200); pinMode(BUTTON_PIN, INPUT_PULLUP); WiFi.mode(WIFI_AP_STA); // Start local captive hotspot portal architecture on channel 12 WiFi.softAP("EMERGENCY_SOS_NODE", NULL, WIFI_CHANNEL); delay(500); // Force register overrides to hold channel frequency lock tight esp_wifi_set_channel(WIFI_CHANNEL, WIFI_SECOND_CHAN_NONE); dnsServer.start(DNS_PORT, "*", WiFi.softAPIP()); server.on("/", handleRoot); server.on("/submit", handleSubmit); server.on("/generate_204", handleRoot); server.onNotFound(handleRoot); server.begin(); Serial.println("Offline Portal Online."); if (esp_now_init() != ESP_OK) { Serial.println("Error initializing ESP-NOW"); return; } // Configure peer identification variables memset(&peerInfo, 0, sizeof(peerInfo)); memcpy(peerInfo.peer_addr, broadcastAddress, 6); peerInfo.channel = WIFI_CHANNEL; peerInfo.encrypt = false; if (esp_now_add_peer(&peerInfo) != ESP_OK){ Serial.println("Failed to add target receiver peer"); return; } Serial.print("Receiver link configuration complete. Hardware Locked Channel: "); Serial.println(WIFI_CHANNEL); } void loop() { dnsServer.processNextRequest(); server.handleClient(); if (digitalRead(BUTTON_PIN) == LOW) { Serial.println("Physical Backup Button Pressed!"); sendEmergencyPacket("CRITICAL: Manual Hardware Button Pressed!"); delay(2000); } }The Receiver Node (The Gateway Hub): You upload code to the second ESP32 that forces its radio to stay locked onto Radio Channel 12, listening for that fast ESP-NOW broadcast.
\\reciever code #include <WiFi.h> #include <esp_now.h> #include <esp_wifi.h> #include <SPI.h> #include <LoRa.h> #include <WebServer.h> // --- Hardware Pins --- #define SS 5 #define RST 14 #define DIO0 2 #define BUILTIN_LED 2 // --- Data Structure (Matches Sender perfectly) --- typedef struct struct_message { char msg[64]; int floor_num; } struct_message; struct_message incomingData; // --- System State Flags --- int activeFloor = 0; String activeMessage = "System Clear"; volatile bool alertReceivedFlag = false; WebServer server(80); // --- HTML Dashboard Page Layout Engine --- void handleRootPage() { String page = "<!DOCTYPE html><html><head>"; page += "<meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">"; page += "<meta http-equiv=\"refresh\" content=\"1\">"; page += "<style>body{font-family:sans-serif; text-align:center; padding:50px; margin:0; transition:0.3s;} "; page += ".box{background:white; padding:30px; border-radius:10px; display:inline-block; box-shadow:0 4px 8px rgba(0,0,0,0.1); margin-top:50px;} "; page += "</style></head>"; if(!alertReceivedFlag) { page += "<body style=\"background:#2ecc71;\">"; page += "<div class=\"box\">"; page += "<h1 style=\"color:#2ecc71;\">🟢 SYSTEM MONITOR ONLINE</h1>"; page += "<p>Status: Awaiting wireless node triggers...</p>"; page += "</div>"; } else { page += "<body style=\"background:#e74c3c;\">"; page += "<div class=\"box\">"; page += "<h1 style=\"color:#e74c3c;\">🚨 CRITICAL EMERGENCY</h1>"; page += "<h2>LOCATION: FLOOR " + String(activeFloor) + "</h2>"; page += "<p>MESSAGE: <strong>" + activeMessage + "</strong></p>"; page += "</div>"; } page += "</body></html>"; server.send(200, "text/html", page); } // --- ESP-NOW Safe Callback --- void OnDataRecv(const uint8_t * mac, const uint8_t *incomingDataRaw, int len) { if (len >= sizeof(struct_message)) { memcpy(&incomingData, incomingDataRaw, sizeof(struct_message)); activeFloor = incomingData.floor_num; activeMessage = String(incomingData.msg); alertReceivedFlag = true; } } void setup() { Serial.begin(115200); delay(500); pinMode(BUILTIN_LED, OUTPUT); digitalWrite(BUILTIN_LED, LOW); Serial.println("\n--- RUNNING HARDWARE CONFIGURATION MATRIX ---"); WiFi.disconnect(true); WiFi.mode(WIFI_AP_STA); delay(100); // MATCH FIXED: Setting third argument to 12 locks the Receiver Access Point to Channel 12! if(WiFi.softAP("FlareX_Emergency_Net", "12345678", 12, 0)) { Serial.print("✅ Access Point Active. Link: http://"); Serial.println(WiFi.softAPIP()); } // Lock internal hardware radio lanes to Channel 12 permanently esp_wifi_set_channel(12, WIFI_SECOND_CHAN_NONE); Serial.println("✅ Hardware Radio Lane locked to Channel 12."); // Initialize Web Server Routes server.on("/", handleRootPage); server.begin(); Serial.println("✅ Local Dashboard Server Online."); // Initialize Physical LoRa Radio LoRa.setPins(SS, RST, DIO0); if (!LoRa.begin(433E6)) { Serial.println("❌ Hardware Error: LoRa Shield Disconnected!"); while(1); } Serial.println("...LoRa Transceiver Hardware Ready."); // Initialize ESP-NOW Protocol Link if (esp_now_init() != ESP_OK) { Serial.println("❌ Protocol Error: ESP-NOW Core Failed!"); return; } esp_now_register_recv_cb(esp_now_recv_cb_t(OnDataRecv)); Serial.println("🏁 SYSTEM ACTIVE: Awaiting wireless node triggers...\n"); } void loop() { server.handleClient(); if (alertReceivedFlag) { digitalWrite(BUILTIN_LED, HIGH); Serial.println("\n=============================================="); Serial.println("🚨 PACKET CAPTURED: BROADCASTING REAL-TIME UI"); Serial.print("🏢 LOCATION : Floor "); Serial.println(activeFloor); Serial.print("⚠️ SIGNAL : "); Serial.println(activeMessage); Serial.println("=============================================="); // Deploy outbound LoRa relay broadcast LoRa.beginPacket(); LoRa.print("ALERT|Floor:"); LoRa.print(activeFloor); LoRa.print("|Msg:"); LoRa.print(activeMessage); LoRa.endPacket(); delay(100); digitalWrite(BUILTIN_LED, LOW); } delay(1); }
Step 4: The Live Demonstration Sequence
- Power Up: Turn on both completed hardware setups using USB cables or batteries.
- Connect to Hub: Take a smartphone or laptop, open the Wi-Fi settings, and connect directly to the offline network named
FlareX_Emergency_Net. - Open Dashboard: Open any web browser and type in
http://192.168.4.1. The screen will load a clean, calm emerald-green background showing the system is safely monitoring. - Press the Button: Press the physical push button on the Sender Node.
- The Instant Result: The Receiver catches the signal using a fast memory interrupt, triggers its physical on-board LED, relays the distress data over long-distance 433MHz LoRa waves to outside rescue camps, and instantly forces the browser web dashboard to flip to a flashing emergency red alert screen displaying the exact floor location.
