Originally posted on MAKE:
Starting the project I needed to figure out how to interface a RFID reader with the Pi. I wanted to interface it with the UART pins but due to time constraints I ended up using a sparkfun USB adapter with my Innovations ID-20 RFID reader. The only thing I has to do was monitor the USB in /dev and receive the RFID tag ID when someone scanned their card. To do this I used python script that monitored serial connection on /dev/ttyUSB0 the base of the script which I have posted to my github account and used a sqlite3 database to verify if the card scanned was a valid member, if so it would trigger the door. Also used a RGB LED to notify if the card was good or not.