I can not find my schematic but...

Using the Nano Socket IWifi.

Header J8 iWifi pin 8 connect to pin 12 max232
Header J8 iWifi pin 9 connect to pin 11 max 232

Max232 pin 13 connect to PC DB9 pin 3
Max232 pin 14 connect to PC DB9 pin 2

And the grounds (zero rail) are all common.