RS232 to RS485 Converter specification
We have a very simple RS232 converter design that is well documented and free. The direction of data communication is controlled directly by the RTS line in that design - it works really well with custom software or hardware, but windows does not operate RTS with the precision required for reliable operation. This model of RS485 converter overcomes the RTS issue by using a microprocessor and switching on Data transfer. There is a greater complexity to the design, however. We sell this unit (mostly to) local Australian companies. This design has been relatively trouble free, and if you require quantities we can adapt the connector pinout to suit your application - however then the device will no longer fit the simple little D25 case in which you see it pictured.
The RS232 to RS485 converter
The RS485 converter circuit diagram