hello yogi,
Max 232 is the simplest ckt… i dont knw why you getting such problem… any ways check out these steps…
1) just short the pin 2 and 3 of the serial port then open terminal and see weather you geeting echo….
if the above step goes perfect then you are able to open the serial porst of you PC check with step two…
2) Now make Max232 connections short pin 11 and 12 instead of sending it to controller and see weather you getting echo…