Rescan tokens that can have unstable identifiers to make sure that the ID of the token presented is stable

AfRApay.MateCard/include/cardReader.h

@@ -5,8 +5,10 @@
 
 class CardReader {
 public:
+	virtual bool canHaveUnstableIdentifier() = 0;
 	virtual bool isNewCardPresent() = 0;
 	virtual String getCardUid() = 0;
+	virtual void reset() = 0;
 };
 
 class MFRC522CardReader : public CardReader {
@@ -14,8 +16,10 @@ private:
 	MFRC522* iReader;
 public:
 	explicit MFRC522CardReader(MFRC522* reader);
+	bool canHaveUnstableIdentifier() override;
 	bool isNewCardPresent() override;
 	String getCardUid() override;
+	void reset() override;
 };
 
 class RDM6300CardReader : public CardReader {
@@ -23,6 +27,8 @@ private:
 	Rdm6300* iReader;
 public:
 	explicit RDM6300CardReader(Rdm6300* reader);
+	bool canHaveUnstableIdentifier() override;
 	bool isNewCardPresent() override;
 	String getCardUid() override;
+	void reset() override;
 };

AfRApay.MateCard/include/utils.h

@@ -13,7 +13,8 @@ enum e_state {
 	STATE_IDLE,
 	STATE_TRANSACT_CARDSCAN,
 	STATE_TRANSACT_VERIFY,
-	STATE_LINK_CARDSCAN,
+	STATE_LINK_CARD_SCAN,
+	STATE_LINK_CARD_RESCAN,
 	STATE_LINK_VERIFY,
 	STATE_BALANCE_CARDSCAN,
 	STATE_BALANCE_VERIFY,

AfRApay.MateCard/src/cardReader.cpp

@@ -16,6 +16,16 @@ String MFRC522CardReader::getCardUid() {
 	return byteArrayAsHexString(iReader->uid.uidByte, iReader->uid.size);
 }
 
+void MFRC522CardReader::reset() {
+	iReader->PCD_AntennaOff();
+	iReader->PCD_Init();
+	iReader->PCD_AntennaOn();
+}
+
+inline bool MFRC522CardReader::canHaveUnstableIdentifier() {
+	return true;
+}
+
 RDM6300CardReader::RDM6300CardReader(Rdm6300* reader) {
 	iReader = reader;
 }
@@ -30,3 +40,15 @@ String RDM6300CardReader::getCardUid() {
 	sprintf(buf, "%010u", uid);
 	return {buf};
 }
+
+void RDM6300CardReader::reset() {
+	/*
+	 * We don't need to do anything here
+	 * RDM6300 readers don't report a new card as present til the old card is removed and re-presented
+	 */
+}
+
+inline bool RDM6300CardReader::canHaveUnstableIdentifier() {
+	// As far as I am aware, there are no 125khz tags with unstable identifiers
+	return false;
+}

AfRApay.MateCard/src/main.cpp

@@ -33,6 +33,7 @@ String apiUrl = "";
 const int gTimeout = 5000;
 const int scanTimeout = 15000;
 
+CardReader* scannedCardReader;
 String scannedCardId = "";
 String lastStatusText = "";
 
@@ -52,7 +53,7 @@ void IRAM_ATTR LinkInterruptHandler() {
 		return;
 	}
 	interruptFired = true;
-	state = STATE_LINK_CARDSCAN;
+	state = STATE_LINK_CARD_SCAN;
 }
 
 void IRAM_ATTR BalanceInterruptHandler() {
@@ -139,6 +140,7 @@ void loop() {
 			if (reader->isNewCardPresent()) {
 				scannedCardId = reader->getCardUid();
 				lastStatusText = "Card #" + scannedCardId;
+				scannedCardReader = reader;
 				state = STATE_TRANSACT_VERIFY;
 				return;
 			}
@@ -164,19 +166,46 @@ void loop() {
 		lastStatusText = lastStatusText.substring(2);
 		timer = millis();
 		return;
-	case STATE_LINK_CARDSCAN:
+	case STATE_LINK_CARD_SCAN:
 		for (CardReader* reader : readers) {
 			if (reader->isNewCardPresent()) {
+				scannedCardReader = reader;
 				scannedCardId = reader->getCardUid();
-				lastStatusText = "Card #" + scannedCardId;
-				state = STATE_LINK_VERIFY;
-				return;
+				if (reader->canHaveUnstableIdentifier()) {
+					lastStatusText = "Link - rescan";
+					reader->reset();
+					timer = millis();
+					state = STATE_LINK_CARD_RESCAN;
+					return;
+				}
+				else {
+					lastStatusText = "Card #" + scannedCardId;
+					state = STATE_LINK_VERIFY;
+					return;
+				}
 			}
 		}
 		if (!cooldownCheck(scanTimeout)) {
 			updateOLED(u8g2, state, "Link", String(cooldownSecondsRemaining(scanTimeout, timer)));
 		}
 		break;
+	case STATE_LINK_CARD_RESCAN:
+		if (scannedCardReader->isNewCardPresent()) {
+			if (scannedCardId == scannedCardReader->getCardUid()) {
+				lastStatusText = "Card #" + scannedCardId;
+				state = STATE_LINK_VERIFY;
+				return;
+			}
+			else {
+				lastStatusText = "Unstable identifier";
+				state = STATE_RESULT_FAILURE;
+				return;
+			}
+		}
+		if (!cooldownCheck(scanTimeout)) {
+			updateOLED(u8g2, state, "Link - rescan", String(cooldownSecondsRemaining(scanTimeout, timer)));
+		}
+		break;
 	case STATE_LINK_VERIFY:
 		updateOLED(u8g2, state, lastStatusText);
 		tone(PIN_BUZZER, NOTE_A5, 25);

AfRApay.MateCard/src/oled.cpp

@@ -100,7 +100,8 @@ void updateOLED(U8G2 u8g2, e_state state, const String& statusText, const String
 		break;
 	case STATE_TRANSACT_CARDSCAN:
 	case STATE_BALANCE_CARDSCAN:
-	case STATE_LINK_CARDSCAN:
+	case STATE_LINK_CARD_SCAN:
+	case STATE_LINK_CARD_RESCAN:
 		drawLogo(u8g2, LOGO_CONTACTLESS);
 		break;
 	case STATE_RESULT_SUCCESS: