If I want to receive something over RS485 I pull RE and DE low. This is tested and works good. The same thing with sending: RE and DE high, sending works, everybody is happy.
Now, sometimes I want to work directly with the UART on the board (the RX and TX lines feeding into the ADM2587). This is where stuff gets tricky. To use the UART, I have to do the opposite: for receiving I have to pull RE and DE high, for sending RE and DE low. If I do anything else the ADM seems to pull on it's RX and TX lines, and my microcontroller is not able to communicate properly.
Do I something wrong, or can ADM really not coexist with some other serial communication on it's input lines?? In my ideal dream world, I would have RE constantly low (enabling the receiver), and DE normally low to keep my uart communication on the board. Only if I want to send something out I would enable DE and send data over RS485.
But this results in chaos and mayhem. RS485 is not stable (many bit errors in communication due to wrong voltage levels) and UART doesn't work at all (I can see the received data on the lines, but the LOW voltage does only go to 3V, not all the way down to 0V).
Picture below: RX Signal on the microcontroller pin, RE LOW, DE LOW
Any ideas? how would one implement an "receive only" ADM25XX, where the lines are not held by the chip?