Heres the crash course I give ALL my techs on how to terminate rs232, but we always do custom solder ends on boths sides
-Terminate one side
-On other side connect grounds
-check the pins on the wire you just terminated for voltage, one will have between -4 and -11 volts checking from gnd to the other 2 pins, lets call this Line A, we will call the other line B
-check the unterminated side from gnd(p5) to the other 2 pins (2)(3), one will have voltage between -4 and -11 volts, call this pin B, other other pin we will call pin A
-terminate line A to pin a
-terminate line b to pin b
Perfect connections every time, no need to check pinouts**

very rarely neither line will have voltage, check settings to make sure serial is enabled, if it is, you need to check specs on that device, it will say a line is TX, just assume that pin has voltage, and continue as above.