I bought myself a Serial 13.56MHZ RFID Reader/Writer Module Kit on ebay that came with a RFID tag and card.

I was playing with it and the following code worked like a charm:

#include <SoftwareSerial.h>

SoftwareSerial mySerial(2,3);

unsigned char command, devnull;
unsigned int returnLength;

void setup()  
{
  Serial.begin(9600);

  Serial.println("Waiting for Card\n");
  mySerial.begin(9600);

   mySerial.write(0x02); //Send the command to RFID, please refer to RFID manual
}

void loop()
{
  if (mySerial.available()) {
    Serial.print("\n\rCARD SERIAL: ");
    for (unsigned int i=0; i<4 ;i=i){
      if (mySerial.available()) {
        Serial.print(mySerial.read(),HEX); //Display the Serial Number in HEX
        i++;
      }
    }
    mySerial.write(0x02); //Send the command to RFID, please refer to RFID manual
  }
}       

void Get_Reply() {
  while (!mySerial.available());
  devnull = mySerial.read();
  while (!mySerial.available());
  returnLength = mySerial.read() - 1;

  for (unsigned int i=0;i< returnLength;i=i){
    //Serial.print("2"); 
    if (mySerial.available()) {
      //Serial.print("\n\ri is: ");Serial.print(i);Serial.print(" ");
      Serial.print(mySerial.read(),HEX); //Display the Serial Number in HEX
      Serial.print(" ");
      i++;
    }
  }
}

When I passed a tag over the reader the output was:

Waiting for Card

CARD SERIAL: E298ABB9

I played around more with some more commands I found here:
– Manual
– Test document

I was especially interested in the “wallet functions”. IE how to initialize the wallet, how to deduct from it etc.

And then somehow I messed up… Whatever message I sent to the reader it immediately sent back 0xFF which means a general error. The state led was on but the mode led was always off… weird. Fortunately I got help in the Arduino forum.

The idea was to send the “factory defaults” command to the reader in different baud rates using the Uno’s serial interface. After I did that the mode led was still off and I was disappointed. I thought the module was dead.

But I just uploaded the RFID tag reader sketch up to the UNO and it worked again!

Here’s the code that sends the factory defaults command to the RFID module:

void setup() {
  // put your setup code here, to run once:
 pinMode(13, OUTPUT); 
  delay(1000);
  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);
}

void loop() {
  // put your main code here, to run repeatedly: 

  Serial.begin(2400);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

  Serial.begin(4800);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

   Serial.begin(9600);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

   Serial.begin(14400);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

   Serial.begin(19200);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

   Serial.begin(28800);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

    Serial.begin(38400);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

    Serial.begin(57600);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

    Serial.begin(115200);
  delay(1000);

  Serial.write(0xAB);
  Serial.write(0x02);
  Serial.write(0x0F);

  digitalWrite(13, HIGH);
  delay(1000);  
  digitalWrite(13, LOW);

}