The audio-serial PSP port is only 3.3V output level and can not be used directly to a RS232 device.
This adaptor acts as a RS232 level translator and provides a 5V voltage to connect some small devices.
All the needed files are included in the attached file:
PSP2Serial.sch : Schematics (Eagle 5.0.0)
PSP2Serial.brd : PCB (Eagle 5.0.0)
PSP2Serial-Pcb-lower.png : 600dpi 'Solder layer' (lower side)
PSP2Serial-Pcb.png : 600dpi full board
PSP2Serial-Pcb-Sch.png : 150dpi schematics
Usage
Just connect the board to the audio PSP port and the sub-9 connector to a RS232 device.
Enjoy !
Buzz