I have posted on my other blogs about using the ID12 RFID reader (125 kHz) with the Sparkfun USB Reader Breakout to provide an easy way to connect the RFID reader by a serial (UART) connection to a Raspberry Pi  or an Arduino Uno. While the name of the breakout board makes it clear that it is primarily intended for USB connections, the board breaks out the pins for connecting to the serial pins (digital 0 & digital 1) on the pcDuino.  The simple Python code in this example is the same as the code used with the Raspberry Pi.

For more details, please refer to http://bradsmc.blogspot.com/2013/05/rfid-for-pcduino-using-innovations-id12.html