driver-api/serial/serial-rs485.rst

2 RS485 Serial Communications
8    EIA-485, also known as TIA/EIA-485 or RS-485, is a standard defining the
15 2. Hardware-related Considerations
18    Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in
19    half-duplex mode capable of automatically controlling line direction by
20    toggling RTS or DTR signals. That can be used to control external
21    half-duplex hardware like an RS485 transceiver or any RS232-connected
22    half-duplex devices like some modems.
26    available at user-level to allow switching from one mode to the other, and
33    RS485 communications. This data structure is used to set and configure RS485
36    The device tree can also provide RS485 boot time parameters (see [2]
40    Any driver for devices capable of working both as RS232 and RS485 should
46 4. Usage from user-level
49    From user-level, RS485 configuration can be get/set using the previous
50    ioctls. For instance, to set RS485 you can use the following code::
54 	/* Include definition for RS485 ioctls: TIOCGRS485 and TIOCSRS485 */
65 	/* Enable RS485 mode: */
68 	/* Set logical level for RTS pin equal to 1 when sending: */
70 	/* or, set logical level for RTS pin equal to 0 when sending: */
73 	/* Set logical level for RTS pin equal to 1 after sending: */
75 	/* or, set logical level for RTS pin equal to 0 after sending: */
78 	/* Set rts delay before send, if needed: */
81 	/* Set rts delay after send, if needed: */
103  [2]	Documentation/devicetree/bindings/serial/rs485.txt