Initial commit: project docs and ignore rules

.gitignore

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+.pio
+.vscode/.browse.c_cpp.db*
+.DS_Store

README.md

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+# listener_firmware
+
+**Listener / scanner module** for the dual-PN532 NFC setup: continuously polls NFC tags and forwards data to the emulator over **ESP-NOW**.
+
+## Build
+
+Use PlatformIO from the **parent directory** (see root `platformio.ini`):
+
+```bash
+cd ..
+pio run -e listener
+pio run -e listener -t upload
+```
+
+Includes headers from `../common/`.
+
+## Hardware
+
+Pinout and stack description: [parent README](../README.md).

src/main.cpp

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+#include <Arduino.h>
+#include <WiFi.h>
+#include <esp_now.h>
+#include <Wire.h>
+#include <Adafruit_PN532.h>
+#include "../../common/nfc_protocol.h"
+
+// Pin definitions for ESP32-C3
+#define PN532_SDA 8
+#define PN532_SCL 9
+#define LED_PIN 10
+
+// PN532 instance
+Adafruit_PN532 nfc(PN532_SDA, PN532_SCL);
+
+// Communication variables
+uint8_t emulator_mac[6] = {0};
+bool is_paired = false;
+uint8_t message_sequence = 0;
+unsigned long last_heartbeat = 0;
+unsigned long last_scan = 0;
+const unsigned long SCAN_INTERVAL = 100; // Scan every 100ms
+
+// Function prototypes
+void initializeNFC();
+void initializeESPNow();
+void scanForEmulator();
+void scanNFCTags();
+void sendNFCData(const NFCData& data);
+void sendHeartbeat();
+void onDataSent(const uint8_t *mac_addr, esp_now_send_status_t status);
+void onDataReceived(const uint8_t *mac, const uint8_t *incomingData, int len);
+void blinkLED(int times, int delay_ms = 200);
+
+void setup() {
+    Serial.begin(115200);
+    delay(1000);
+    
+    Serial.println("=== NFC Listener Module Starting ===");
+    
+    // Initialize LED
+    pinMode(LED_PIN, OUTPUT);
+    digitalWrite(LED_PIN, LOW);
+    
+    // Initialize NFC
+    initializeNFC();
+    
+    // Initialize ESP-NOW
+    initializeESPNow();
+    
+    // Start scanning for emulator
+    scanForEmulator();
+    
+    Serial.println("Listener module ready!");
+    blinkLED(3, 100);
+}
+
+void loop() {
+    unsigned long current_time = millis();
+    
+    // Send heartbeat every second if paired
+    if (is_paired && (current_time - last_heartbeat > HEARTBEAT_INTERVAL_MS)) {
+        sendHeartbeat();
+        last_heartbeat = current_time;
+    }
+    
+    // Scan for NFC tags
+    if (current_time - last_scan > SCAN_INTERVAL) {
+        scanNFCTags();
+        last_scan = current_time;
+    }
+    
+    // If not paired, try to find emulator again
+    if (!is_paired && (current_time % 5000 == 0)) {
+        scanForEmulator();
+    }
+    
+    delay(10);
+}
+
+void initializeNFC() {
+    Serial.println("Initializing PN532...");
+    
+    nfc.begin();
+    
+    uint32_t versiondata = nfc.getFirmwareVersion();
+    if (!versiondata) {
+        Serial.println("ERROR: PN532 not found!");
+        while (1) {
+            blinkLED(1, 100);
+            delay(500);
+        }
+    }
+    
+    Serial.print("Found chip PN5"); Serial.println((versiondata>>24) & 0xFF, HEX);
+    Serial.print("Firmware ver. "); Serial.print((versiondata>>16) & 0xFF, DEC);
+    Serial.print('.'); Serial.println((versiondata>>8) & 0xFF, DEC);
+    
+    // Configure board to read RFID tags
+    nfc.SAMConfig();
+    
+    Serial.println("PN532 initialized successfully!");
+}
+
+void initializeESPNow() {
+    Serial.println("Initializing ESP-NOW...");
+    
+    WiFi.mode(WIFI_STA);
+    WiFi.disconnect();
+    
+    if (esp_now_init() != ESP_OK) {
+        Serial.println("ERROR: ESP-NOW init failed!");
+        return;
+    }
+    
+    esp_now_register_send_cb(onDataSent);
+    esp_now_register_recv_cb(onDataReceived);
+    
+    Serial.println("ESP-NOW initialized successfully!");
+}
+
+void scanForEmulator() {
+    Serial.println("Scanning for emulator module...");
+    
+    // Broadcast pairing request
+    CommMessage msg;
+    msg.type = MSG_PAIRING_REQUEST;
+    msg.sequence = message_sequence++;
+    msg.payload_size = 0;
+    msg.checksum = calculateChecksum((uint8_t*)&msg, sizeof(msg) - sizeof(msg.checksum));
+    
+    // Broadcast to all devices
+    uint8_t broadcast_mac[6] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
+    
+    esp_now_peer_info_t peer_info = {};
+    memcpy(peer_info.peer_addr, broadcast_mac, 6);
+    peer_info.channel = ESPNOW_CHANNEL;
+    peer_info.encrypt = false;
+    
+    if (esp_now_add_peer(&peer_info) == ESP_OK || esp_err_t(ESP_ERR_ESPNOW_EXIST)) {
+        esp_now_send(broadcast_mac, (uint8_t*)&msg, sizeof(msg));
+    }
+}
+
+void scanNFCTags() {
+    uint8_t uid[] = { 0, 0, 0, 0, 0, 0, 0 };
+    uint8_t uidLength;
+    
+    if (nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, &uidLength, 50)) {
+        // Tag detected!
+        digitalWrite(LED_PIN, HIGH);
+        
+        NFCData nfc_data = {};
+        
+        // Copy UID
+        nfc_data.uid_length = min(uidLength, (uint8_t)10);
+        memcpy(nfc_data.uid, uid, nfc_data.uid_length);
+        
+        // Get additional tag information
+        uint8_t sak, atqa[2];
+        if (nfc.getTargetInfo(&sak, atqa)) {
+            nfc_data.sak = sak;
+            nfc_data.atqa[0] = atqa[0];
+            nfc_data.atqa[1] = atqa[1];
+        }
+        
+        // Determine tag type
+        if (uidLength == 4) {
+            nfc_data.tag_type = 1; // MIFARE Classic 1K
+        } else if (uidLength == 7) {
+            nfc_data.tag_type = 2; // MIFARE Ultralight
+        } else {
+            nfc_data.tag_type = 0; // Unknown
+        }
+        
+        // Try to read some data from the tag
+        uint8_t data[16];
+        if (nfc.mifareclassic_ReadDataBlock(1, data)) {
+            nfc_data.data_length = min(16, MAX_NFC_DATA_SIZE);
+            memcpy(nfc_data.raw_data, data, nfc_data.data_length);
+        }
+        
+        nfc_data.timestamp = millis();
+        
+        Serial.println("NFC Tag detected!");
+        printNFCData(&nfc_data);
+        
+        // Send data to emulator if paired
+        if (is_paired) {
+            sendNFCData(nfc_data);
+        }
+        
+        digitalWrite(LED_PIN, LOW);
+        
+        // Wait a bit to avoid multiple reads of the same tag
+        delay(500);
+    }
+}
+
+void sendNFCData(const NFCData& data) {
+    if (!is_paired) return;
+    
+    CommMessage msg;
+    msg.type = MSG_NFC_DATA;
+    msg.sequence = message_sequence++;
+    msg.payload_size = sizeof(NFCData);
+    msg.nfc_data = data;
+    msg.checksum = calculateChecksum((uint8_t*)&msg, sizeof(msg) - sizeof(msg.checksum));
+    
+    esp_now_send(emulator_mac, (uint8_t*)&msg, sizeof(msg));
+    
+    Serial.println("NFC data sent to emulator");
+}
+
+void sendHeartbeat() {
+    if (!is_paired) return;
+    
+    CommMessage msg;
+    msg.type = MSG_HEARTBEAT;
+    msg.sequence = message_sequence++;
+    msg.payload_size = 0;
+    msg.checksum = calculateChecksum((uint8_t*)&msg, sizeof(msg) - sizeof(msg.checksum));
+    
+    esp_now_send(emulator_mac, (uint8_t*)&msg, sizeof(msg));
+}
+
+void onDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
+    // Optional: Handle send status
+}
+
+void onDataReceived(const uint8_t *mac, const uint8_t *incomingData, int len) {
+    if (len != sizeof(CommMessage)) return;
+    
+    CommMessage* msg = (CommMessage*)incomingData;
+    
+    if (!validateMessage(msg)) {
+        Serial.println("Invalid message received");
+        return;
+    }
+    
+    switch (msg->type) {
+        case MSG_PAIRING_RESPONSE:
+            if (!is_paired) {
+                memcpy(emulator_mac, mac, 6);
+                is_paired = true;
+                
+                // Add emulator as peer
+                esp_now_peer_info_t peer_info = {};
+                memcpy(peer_info.peer_addr, emulator_mac, 6);
+                peer_info.channel = ESPNOW_CHANNEL;
+                peer_info.encrypt = false;
+                esp_now_add_peer(&peer_info);
+                
+                Serial.println("Paired with emulator!");
+                Serial.print("Emulator MAC: ");
+                for (int i = 0; i < 6; i++) {
+                    Serial.printf("%02X", emulator_mac[i]);
+                    if (i < 5) Serial.print(":");
+                }
+                Serial.println();
+                
+                blinkLED(5, 100);
+            }
+            break;
+            
+        case MSG_ACK:
+            // Handle acknowledgment
+            break;
+    }
+}
+
+void blinkLED(int times, int delay_ms) {
+    for (int i = 0; i < times; i++) {
+        digitalWrite(LED_PIN, HIGH);
+        delay(delay_ms);
+        digitalWrite(LED_PIN, LOW);
+        delay(delay_ms);
+    }
+}