crap:
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The way I figure, the only tricky part is to know when to change data direction, since it does need two way communication in half duplex.
I noticed that you mentioned the controller having RS-422, but I do not see the pins for it on the connector pinout you showed. Does it in fact have RS-422? The reason I ask is RS-422 is electrically very similar to RS-485, except it has separate transmit and receive, whereas RS-485 has them shared. With RS-422 you would not have to worry about switching between transmitting and receiving.