Hello,
Here is a code for reading an RFID chip that i got from the Internet
#include <SPI.h>
#include <MFRC522.h>
#define SS_PIN 10
#define RST_PIN 9
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance.
void setup()
{
Serial.begin(9600); // Initiate a serial communication
SPI.begin(); // Initiate SPI bus
mfrc522.PCD_Init(); // Initiate MFRC522
Serial.println("Approximate your card to the reader...");
Serial.println();
}
void loop()
{
// Look for new cards
if ( ! mfrc522.PICC_IsNewCardPresent())
{
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial())
{
return;
}
//Show UID on serial monitor
Serial.print("UID tag :");
String content= "";
byte letter;
for (byte i = 0; i < mfrc522.uid.size; i++)
{
Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(mfrc522.uid.uidByte[i], HEX);
content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
content.concat(String(mfrc522.uid.uidByte[i], HEX));
}
Serial.println();
Serial.print("Message : ");
content.toUpperCase();
if (content.substring(1) == "BD 31 15 2B") //change here the UID of the card/cards that you want to give access
{
Serial.println("Authorized access");
Serial.println();
delay(3000);
}
else {
Serial.println(" Access denied");
delay(3000);
}
}
And i want the code to show me the cards Number only once when i go over it and keep it on the Sensor so i dont recieve the Cards UID every 1 second on my Serial Monitor.
I want the Code to be built the way that it compares the old value and if it gets a Positive result ( identical Number) i want it to say "remove card" only once and wait for an another Card.
I have tried to campare content.substring(1)) with content.substring(1)) but thats nonsense or is it? i dont know. Im confused. I have tried the infinite While loop and the If Loop but didnt work.
So plz help me