If you need to receive data from the Speedway Revolution reader via a serial connection (RS-232), then you have two options to do so. The reader's serial port is accessed through the GPIO port on the reader as illustrated here:
Option 1: create a serial cable that connects the GPIO port on the reader to a serial device (DB-9):
NOTE: If you don't want to make your own cable, you can order it from this third-party source.
Option 2: create a serial cable that connects to the serial portion of the Impinj SpeedwayR GPIO Box: