Add PN532 self recovery to door firmware

firmware/esp32-pn532-door/src/main.cpp

@@ -13,8 +13,18 @@
 Adafruit_PN532 nfc(PN532_IRQ_PIN, PN532_RESET_PIN, &Wire);
 
 static unsigned long lastReadAt = 0;
+static unsigned long lastWifiAttemptAt = 0;
+static unsigned long lastPn532InitAt = 0;
+static unsigned long lastPn532HealthAt = 0;
 static String lastCredential = "";
 static bool wifiScanPrinted = false;
+static bool pn532Ready = false;
+static uint16_t emptyReadCount = 0;
+
+const unsigned long WIFI_RETRY_MS = 15000;
+const unsigned long PN532_INIT_RETRY_MS = 5000;
+const unsigned long PN532_HEALTH_CHECK_MS = 120000;
+const uint16_t PN532_EMPTY_READ_REINIT_COUNT = 300;
 
 String bytesToHex(const uint8_t *data, uint8_t length) {
   String out;
@@ -114,6 +124,10 @@ void printWifiScan() {
 void connectWifi() {
   if (WiFi.status() == WL_CONNECTED) return;
 
+  unsigned long now = millis();
+  if (lastWifiAttemptAt && now - lastWifiAttemptAt < WIFI_RETRY_MS) return;
+  lastWifiAttemptAt = now;
+
   WiFi.persistent(false);
   WiFi.mode(WIFI_STA);
   WiFi.setSleep(false);
@@ -140,7 +154,59 @@ void connectWifi() {
   }
 }
 
+bool initializePn532(bool force = false) {
+  unsigned long now = millis();
+  if (!force && lastPn532InitAt && now - lastPn532InitAt < PN532_INIT_RETRY_MS) return pn532Ready;
+  lastPn532InitAt = now;
+  pn532Ready = false;
+
+  Serial.println("Initializing PN532...");
+  pinMode(PN532_RESET_PIN, OUTPUT);
+  digitalWrite(PN532_RESET_PIN, LOW);
+  delay(25);
+  digitalWrite(PN532_RESET_PIN, HIGH);
+  delay(120);
+
+  Wire.end();
+  delay(25);
+  Wire.begin(PN532_SDA_PIN, PN532_SCL_PIN);
+  Wire.setClock(100000);
+  Wire.setTimeOut(60);
+
+  nfc.begin();
+  uint32_t version = nfc.getFirmwareVersion();
+  if (!version) {
+    Serial.println("PN532 not found. Will retry without stopping controller.");
+    return false;
+  }
+
+  nfc.SAMConfig();
+  emptyReadCount = 0;
+  lastPn532HealthAt = now;
+  pn532Ready = true;
+  Serial.println("PN532 ready.");
+  return true;
+}
+
+void maintainPn532() {
+  unsigned long now = millis();
+  if (!pn532Ready) {
+    initializePn532();
+    return;
+  }
+
+  if (now - lastPn532HealthAt < PN532_HEALTH_CHECK_MS) return;
+  lastPn532HealthAt = now;
+
+  uint32_t version = nfc.getFirmwareVersion();
+  if (!version) {
+    Serial.println("PN532 health check failed; reinitializing.");
+    initializePn532(true);
+  }
+}
+
 bool readCardUid(uint8_t *uid, uint8_t *uidLength) {
+  if (!pn532Ready && !initializePn532()) return false;
   return nfc.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid, uidLength, 350);
 }
 
@@ -173,7 +239,16 @@ String readMifareSecret(uint8_t *uid, uint8_t uidLength) {
 String readCredential() {
   uint8_t uid[7] = { 0 };
   uint8_t uidLength = 0;
-  if (!readCardUid(uid, &uidLength)) return "";
+  if (!readCardUid(uid, &uidLength)) {
+    emptyReadCount++;
+    if (emptyReadCount >= PN532_EMPTY_READ_REINIT_COUNT) {
+      Serial.println("PN532 idle/read timeout threshold reached; reinitializing.");
+      initializePn532(true);
+    }
+    return "";
+  }
+
+  emptyReadCount = 0;
 
 #if CARD_MODE == CARD_MODE_MIFARE_CLASSIC_BLOCK
   String secret = readMifareSecret(uid, uidLength);
@@ -215,20 +290,12 @@ void setup() {
 
   connectWifi();
 
-  Wire.begin(PN532_SDA_PIN, PN532_SCL_PIN);
+  initializePn532(true);
-  nfc.begin();
-  uint32_t version = nfc.getFirmwareVersion();
-  if (!version) {
-    Serial.println("PN532 not found. Check wiring and mode switches.");
-    while (true) delay(1000);
-  }
-
-  nfc.SAMConfig();
-  Serial.println("PN532 ready.");
 }
 
 void loop() {
   connectWifi();
+  maintainPn532();
 
   String credential = readCredential();
   if (!credential.length()) {