Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
If you make some assumptions and use some tricks the RS-232 to RS-485 half-duplex (2-wire) converter can be quite simple (see attached circuit) ..
Assumption1: Most of Laptop and PC COMs will happily accept 0-5V level on Rx pin ..
Trick1: Steal power from serial port ..
The resultant circuit is self-powered, will work with any baud rate >115kbs and doesn't need direction control (automatically switches from transmission to reception) ..
There are, as usual, small drawbacks .. but who cares about them if circuit works OK ..