Usually a master/slave configuration is half duplex. Why? The master sends out a packet to the addressed slave, the addressed slave decodes the packet and responds. This is half duplex by nature as only one device is talking at one time. The code you presented could be half or full duplex - as for RS485 control, I saw no code to do this.

So, do you really need full duplex?

Controlling the 485 transceiver is only a couple of lines of code - you enable the transmitter when you want to transmit, when transmission is finished, you disable the transmitter. Search out the code I've previously posted and you'll see an example of RS485 transceiver control.