When compiling the code with the MFRC522 library, I encountered an error in `MFRC522Extended.cpp`. The error involves an ordered comparison of a pointer with an integer.

[vidura2]

OS version: Windows 11 Arduino IDE version: 2.3.3 MFRC522 Library version: 1.4.11 Arduino device: ESP32 MFRC522 device: RC522 RFID Module

Affected file(s) or example(s):

MFRC522Extended.cpp

Steps to reproduce:

Add the MFRC522 library to the Arduino project.
Compile a program using the ESP32 and RC522 RFID Module.
Encounter the compilation error.

ERROR: e:\Arduino IDE\libraries\MFRC522\src\MFRC522Extended.cpp: In member function 'MFRC522::StatusCode MFRC522Extended::TCL_Transceive(TagInfo, byte, byte, byte, byte)': e:\Arduino IDE\libraries\MFRC522\src\MFRC522Extended.cpp:824:34: error: ordered comparison of pointer with integer zero ('byte' {aka 'unsigned char'} and 'int') 824 | if (backData && (backLen > 0)) { | ~~^ e:\Arduino IDE\libraries\MFRC522\src\MFRC522Extended.cpp:847:42: error: ordered comparison of pointer with integer zero ('byte' {aka 'unsigned char'} and 'int') 847 | if (backData && (backLen > 0)) { | ~~^

The code :

include

include

include

include

include // Library for AES encryption

// WiFi credentials (if needed, currently commented out) // const char ssid = "ESP32_Access_Point"; // const char password = "123456789";

// RFID setup

define SS_PIN 5 // CS/SDA pin for RFID

define RST_PIN 22 // RST pin for RFID

define RELAY_PIN 25 // Relay control pin

MFRC522 rfid(SS_PIN, RST_PIN);

// Authorized RFID UIDs (replace these with your own values) byte managerKeyUID[4] = {0x3A, 0xC9, 0x6A, 0xCB}; byte secretaryKeyUID[4] = {0x30, 0x01, 0x8B, 0x15};

// Rolling code setup byte rollingCode[4] = {0x00, 0x00, 0x00, 0x01}; // Initial rolling code byte validRollingCode[16]; // Encrypted rolling code

// AES encryption key and initialization vector (IV) byte aesKey[16] = {0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F}; byte aesIV[16] = {0x00};

// WebServer for access log

include

WebServer server(80);

// Log for RFID access attempts String loggedEntries = ""; String systemStatus = "";

// Time synchronization void setupTime() { configTime(0, 0, "pool.ntp.org"); setenv("TZ", "UTC-5", 1); // Adjust timezone to your location tzset();

struct tm timeinfo;
int retryCount = 0;
while (!getLocalTime(&timeinfo) && retryCount < 5) {
    Serial.println("Failed to sync time, retrying...");
    delay(1000);
    retryCount++;
}

if (retryCount == 5) {
    systemStatus = "Failed to sync time, using default time.";
} else {
    systemStatus = "Time synchronized.";
}

}

// Get the current time as a string String getTime() { struct tm timeinfo; if (!getLocalTime(&timeinfo)) { return "Failed to obtain time"; } char timeStr[50]; strftime(timeStr, sizeof(timeStr), "%Y-%m-%d %H:%M:%S", &timeinfo); return String(timeStr); }

// Serve login page void handleLoginPage() { String html = ""; html += "

RFID Door Lock System

"; html += "

System Status: " + systemStatus + "

"; html += ""; html += ""; html += loggedEntries; html += "

UID	Date	Time

";

server.send(200, "text/html", html);

}

// Log RFID entry with UID and timestamp void logEntry(byte uid[]) { String uidStr = ""; for (int i = 0; i < 4; i++) { uidStr += String(uid[i], HEX); if (i < 3) uidStr += ":"; }

String dateTime = getTime();
String date = dateTime.substring(0, 10); // Extract date (YYYY-MM-DD)
String time = dateTime.substring(11);    // Extract time (HH:MM:SS)

String log = "<tr><td>" + uidStr + "</td><td>" + date + "</td><td>" + time + "</td></tr>";
loggedEntries += log;

}

// Check if RFID UID is authorized bool isAuthorizedUID(byte uid[], byte authorizedUID[]) { for (int i = 0; i < 4; i++) { if (uid[i] != authorizedUID[i]) { return false; } } return true; }

// Encrypt rolling code using AES void encryptRollingCode(byte code[], byte encryptedCode[]) { AESLib aes; aes.encrypt(code, 16, encryptedCode, aesKey, 128, aesIV); }

// Decrypt rolling code using AES void decryptRollingCode(byte encryptedCode[], byte decryptedCode[]) { AESLib aes; aes.decrypt(encryptedCode, 16, decryptedCode, aesKey, 128, aesIV); }

// Generate new rolling code void generateNewRollingCode() { for (int i = 0; i < 4; i++) { rollingCode[i] = (rollingCode[i] + random(1, 255)) % 255; } encryptRollingCode(rollingCode, validRollingCode); }

// Check if rolling code is valid bool isValidRollingCode(byte currentCode[]) { byte decryptedCode[16]; decryptRollingCode(validRollingCode, decryptedCode);

for (int i = 0; i < 4; i++) {
    if (currentCode[i] != decryptedCode[i]) {
        return false;
    }
}
return true;

}

void setup() { Serial.begin(115200);

// Start WiFi access point (optional)
// WiFi.softAP(ssid, password);
// systemStatus = "Access Point started. IP Address: " + WiFi.softAPIP().toString();

// Initialize RFID
SPI.begin();
rfid.PCD_Init();
pinMode(RELAY_PIN, OUTPUT);
digitalWrite(RELAY_PIN, HIGH); // Lock the door by default

// Start web server for log display
server.on("/", handleLoginPage);
server.begin();

// Setup time synchronization
setupTime();

// Initialize rolling code encryption
encryptRollingCode(rollingCode, validRollingCode);

}

void loop() { server.handleClient(); // Handle web server requests

// Check for RFID card/tag
if (rfid.PICC_IsNewCardPresent() && rfid.PICC_ReadCardSerial()) {
    if (isAuthorizedUID(rfid.uid.uidByte, managerKeyUID) || isAuthorizedUID(rfid.uid.uidByte, secretaryKeyUID)) {

        // Validate the rolling code
        if (isValidRollingCode(rfid.uid.uidByte)) {
            logEntry(rfid.uid.uidByte); // Log the access
            digitalWrite(RELAY_PIN, LOW); // Unlock door
            delay(2000); // Keep door unlocked for 2 seconds
            digitalWrite(RELAY_PIN, HIGH); // Lock door

            // Generate new rolling code
            generateNewRollingCode();
            systemStatus = "Access granted and rolling code updated.";
        } else {
            systemStatus = "Invalid rolling code!";
        }
    } else {
        systemStatus = "Unauthorized access attempt.";
    }

    // Halt RFID reader
    rfid.PICC_HaltA();
    rfid.PCD_StopCrypto1();
}

}

[gcandrade10]

Same error here

[vidura2]

added a pull request

[syn-arch]

same

[frivera26]

El problema se resuelve de la siguiente manera:

if (backData && (*backLen > 0)) {

y ya puedo usar el RFID-RC522