RFID Arduino

gistfile1.ino

// Ebay RFID decoder by Aaron Christiansen
// Original article: http://thetransistor.com/2011/10/hacking-cheap-rfid-readers/
// Optimizations by Leandro Pereira

// NOTE: this uses the NewSoftwareSerial beta 11
// by Mikal Hart, available here:
// http://arduiniana.org/2011/01/newsoftserial-11-beta/

#include <SoftwareSerial.h>

SoftwareSerial rfid(7, 4);

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

void loop(){
  if (rfid.available()) {
    int len;
    char *in;
    
    in = readRFID(&len);
    if (!len) return;
    Serial.print("Read RFID; len=");
    Serial.print(len);
    Serial.print("; code=");
    Serial.println(in);
  }
}

char* readRFID(int *length)
{
  static char output[10];
  unsigned long timer = millis() + 250;
  int index = 0;

  while (index < sizeof(output) && timer > millis()) {
    if (!rfid.available()) continue;
    const int temp = rfid.read();
    if (temp >= 29 && temp <= 39)
       output[index++] = (temp - 29) % 10 + '0';
  }

  rfid.flush();

  *length = index;
  return output;
}