mk8/libmodbus — comment on commit 14c5807a41230ca9299f55d2ee569cc1120561bd
File: src/modbus-rtu.c line 287
By mk8:

Reading stty documentation I discovered that it is possibile to use RTS signal in hardware to realize the handshake with external device. In RS485 this signal not exist, but sometimes is used to switch between transmission and receiving data.
This is the case on device that I use but unfortunally not works.
In other cases I hope that this can help.

Obviusly if RTS_HW is used, the function to set and reset RTS bit is not more used.