A pretty picture but not much help. You should post a schematic showing all connections and links to the technical information on the hardware parts. Hint: Look up termination on RS485 networks. In your case the network must be terminated to avoid data corruption and unwanted reflections. You will find the termination resistors need to be at the physical ends of the bus. 120 Ohm would be a good starting point. Good luck and let us know how you do.