have u tried using serout2 and serin2. i had the same problem b4 i need one to control a hf modem and another to communicate with a gps module. the modem connected with a max232 via pin c6 and c7 the standard rx tx pins while i just used porta.0 and a.1 for serin2 and serout3 with the gps module and everything is ok.. yes u can also use a specific baudrate. no need a level converter. read the manual for more info on serout and serin command.