Simple example of reading the 125Khz RFID module RDM630

rfid_simple.pde

#include <SoftwareSerial.h>

// Pin definitions
const int rfid_irq = 0;
const int rfid_tx_pin = 6;
const int rfid_rx_pin = 7;

// For communication with RFID module
SoftwareSerial rfid(rfid_tx_pin, rfid_rx_pin);

// Indicates that a reading is now ready for processing
volatile bool ready = false;

// Buffer to contain the reading from the module
uint8_t buffer[14];
uint8_t* buffer_at;
uint8_t* buffer_end = buffer + sizeof(buffer);

void rfid_read(void);

void setup(void)
{
  // Open serial connection to host PC to view output
  Serial.begin(57600);
  Serial.println("rfid_simple");

  // Open software serial connection to RFID module
  pinMode(rfid_tx_pin,INPUT);
  rfid.begin(9600);

  // Listen for interrupt from RFID module
  attachInterrupt(rfid_irq,rfid_read,FALLING);
}

void loop(void)
{
  if ( ready )
  {
    ready = false;

    // Print the buffer
    Serial.print("Reading: ");

    const uint8_t* bp = buffer;
    while ( bp < buffer_end )
      Serial.print(*bp++);

    Serial.println();
  }
}

void rfid_read(void)
{
  // Read characters into the buffer until it is full
  buffer_at = buffer;
  while ( buffer_at < buffer_end )
    *buffer_at++ = rfid.read();

  // Signal that the buffer has data ready
  ready = true;
}