Half-duplex RS-485 direction control support

### Describe the requested feature Hi, Is it possible to add support for half-duplex RS-485 with RE/DE direction control? Is there any plan or workaround to handle this in the current Modbus implementation? Thanks! ### Motivation Right now the Modbus node always works in full-duplex mode, but in some hardware setups we need to toggle a GPIO pin to switch between TX and RX.