I recently completed an RFID project using an Arduino and the Parallax RFID Serial Card Reader - here are the hardware and software notes on making it all work.
1 - Arduino ( I am using an UNO R3 for this demo)
2 - Parallax RFID Serial Card Reader
3 - Solderless Breadboard
Step 1: Wiring the RFID Reader
Insert the RFID board into the solderless breadboard.
Jumper 5V to VCC on the RFID Board
Jumper GND to GND on the RFID Board
Jumper Digital IO pin 2 on the Arduino to /Enable on the RFID Board
Jumper Digital IO pin 5 on the Ardunio to SOUT on the RFID Board
If you power up the Arduino the LED on the RFID Reader should light green. In the next steps we will load the library and code to make the reader work.
Step 2: Loading the SoftwareSerial Library
The SoftwareSerial Library is a core library for Arduino - there should be no need to install it. If you need to install it for some reason, visit the Arduino site.
Step 3: RFID Sketch
Load the RFID Sketch below. The Sketch uses the Serial Monitor on the Arduino IDE to output the reader data at 9600 baud.
The Sketch also uses the SoftwareSerial library to make a connection to the SOUT pin on the reader at 2400 baud using Pin 2 on the Arduino.
The /Enable pin must be held low for the reader to work. The LED turns RED when the Reader is enabled.
Each tag read will be stored in the RFIDTAG variable. Note that the reader will continually read a tag that is within range, so the code "remembers" the last tag and ignores duplicate reads.