RFID- reading block data

Projects Programming
1

Hello there,

I am trying to read block 6 on the RFID tag which has data stored as uint16_t in it.
The problem is that I am constantly seeing weird symbols such as "⸮TT⸮".
Anyone knows how to read data of that block as a String.

Thanks in advance.

2

Two things: this is not an installation and troubleshooting issue, and we can't see your code

3

Sorry for that, I changed it.
I am new at this so have that in mind when your eyes start hurting... :smile:


#include <SPI.h>
#include <MFRC522.h>
#define RST_PIN         7           
#define SS_PIN          10          
MFRC522 mfrc522(SS_PIN, RST_PIN);  
MFRC522::MIFARE_Key key;
MFRC522::StatusCode status;

void setup() {
Serial.begin(9600);                                         
SPI.begin();                                                  
mfrc522.PCD_Init();                                             
Serial.println(F("Read personal data on a MIFARE PICC:"));   
}

void loop() {

for (byte i = 0; i < 6; i++) key.keyByte[i] = 0xFF;
byte block;
byte len;
//-------------------------------------------

if ( ! mfrc522.PICC_IsNewCardPresent()) {
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial()) {
return;
}
Serial.println(F("**Card Detected:**"));
byte buffer1[18];
block = 6;
len = 18;
status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, 4, &key, &(mfrc522.uid));
if (status != MFRC522::STATUS_OK) {
Serial.print(F("Authentication failed: "));
Serial.println(mfrc522.GetStatusCodeName(status));
return;
}
status = mfrc522.MIFARE_Read(block, buffer1, &len);
if (status != MFRC522::STATUS_OK) {
Serial.print(F("Reading failed: "));
Serial.println(mfrc522.GetStatusCodeName(status));
return;
}
String value;
for (byte i = 0; i < 16; i++)
{
Serial.println(buffer1[i]);
value +=(char) buffer1[i];
}

Serial.println("hit me with a brick please");

Serial.println("try 3 GOD PLEASE");
for(int i=0;i<16;i++){
  
  Serial.print(value[i]);
}
Serial.println(F("\n**End Reading**\n"));
delay(1000);
mfrc522.PICC_HaltA();
mfrc522.PCD_StopCrypto1();
}
4 
    byte buffer1[18];
    block = 6;
    len = 18;
    ...
    status = mfrc522.MIFARE_Read(block, buffer1, &len);
    ...
    for (byte i = 0; i < 16; i++)
    }

likely there are other problems, but your code is making some assumptions. would be better to use the # of bytes read from the read function. also report the value returned in "len"

#define BUF_SIZE 18
    len = BUF_SIZE;
    byte buffer1[BUF_SIZE];
    block = 6;
    ...
    status = mfrc522.MIFARE_Read(block, buffer1, &len);
    ...
    for (byte i = 0; i < len; i++)
    }
5

So the problem remains
Output of this:

Serial.print(buffer1[i]);

Is : 2364841184112323000060919362144138

And the output of this

value +=(char) buffer1[i];
Serial.print(value[i]);

Is: ⸮TT⸮

As I know uint16_t is not readable so I need to convert it to String to read it. I tried tons of things and it isn't working...

The real output should be something like this: 1260290024340980<[]>

6

"buffer1 [i]" is a single char

don't you want

Serial.print(buffer1);

if it is a NUL terminated c-ctring?

7

Why not simply print the hex value?

8

I tried that also, but it isn't working, maybe I am wrong, can you describe how to do it?

Serial.print(value[i] , HEX);

Something like that?

As I said, I want to read block 6 of the RFID tag memory, and Block 6 contains 16 bytes:

  • 2 bytes, uint16_t var1 ( for example 1260)
  • 2 bytes, uint16_t var2 ( 2900)
  • 2 bytes, uint16_t var3 ( 2434)
  • 2 bytes, uint16_t var4 (0980)
  • 4 bytes, uint8_t dummy
  • 4 bytes, char

I just want to read the first 4 things. If anyone can help I would be very grateful.
Thanks in advance and sorry if my question is absolutely stupid.