You probably don't really want documentation on the RS-232 standard. It's just a definition of what voltages represent which logic state, and how quickly those voltages change. You also probably don't want to design a circuit to process it; the voltage level circuitry is available in chip form (MAX232, for example) and the timing circuitry is built in to just about every microcontroller sold (it's called a UAR/T).
What you probably
really want is documentation on the Dashboard data format. That can be found here:
http://www.ifirobotics.com/dashboard_viewer.shtml