maybe u can try this design, let me know out-come result.http://rapidshare.com/files/323503276/RS232_RS485_ISOLATE.pdf
RS232 iso--> RS485/RS422Posted on: December 20, 2009, 11:47:25 23:47 - Automerged
here is another one isolation conccept designhttp://rapidshare.com/files/323511550/RS485_repeater.rar
2 similar design given, cheer
you'll have idea make your own iso.RS485/RS422 now, don't forget to share your design.