I'd like to build a DMX512 device.
The problem I have is how to decouple the device from the bus. I decided to use opto-isolators, but how should I wire the diode part of the isolator?
Since I need TTL/RS232 levels on the controller side, I'm using either a MAX485 or ADM485 to convert the RS485 levels (DMX512 is just an implementation using RS485) to TTL/UART levels. But where and how should I use the opto-isolator? Before or after the MAX485?
I was thinking before, right at the bus, but I'm not quite sure how the circuit should look like.
The device is only supposed to receive, not send to the bus.