Easiest place to start with RS485?

I want to hack some sensors that has a RS485 serial bus interface, I am not sure if the RS232-module can be modified, or if I need to start somewhere else?

The simplest route would be something like http://www.rs232-to-rs485.com/

For me on EMX RS232 to RS485 converter didn’t work so Im end with USB To RS485 converter and use it as USBserial port…

Do you have any details as to why it was not working?

I don’t remember right because it is more than 1 year ago when Im try do this.
If I remember right is something with RE/DE signals which can’t be triggered fast enought and Im losing data… Option is RLP(Is somewhere code how to do this) but also something doesn’t work for me(doesnt compile) so easiest way for me has been using USB<->RS486(FT232R + SP481)…