I was looking at some of my previous RS485 projects and there I had to use DE & RE pins on the transceiver module when transmitting. So this might require another pin when the ATU wants to transmit data.To avoid collisions, usually one "node" is the master (e.g. also for modbus) talking to a specific unit, and that one then does reply. With the current scheme it would be possible that the ATU sends status while the controller sends a command at the same time. One possible approach would be to only let the ATU reply with the current status on request (e.g. 'S' command).
Maybe it would also be nice to have some functionality to directly set the tuning values. A smart controller could then recall previous tuning solutions depending on frequency fetched e.g. via rigctl.
73 de OE6HKE
