[deliverable/linux.git] / Documentation / devicetree / bindings / serial / rs485.txt

* RS485 serial communications

The RTS signal is capable of automatically controlling line direction for
the built-in half-duplex mode.
The properties described hereafter shall be given to a half-duplex capable
UART node.

Required properties:
- rs485-rts-delay: prop-encoded-array <a b> where:
  * a is the delay between rts signal and beginning of data sent in milliseconds.
      it corresponds to the delay before sending data.
  * b is the delay between end of data sent and rts signal in milliseconds
      it corresponds to the delay after sending data and actual release of the line.

Optional properties:
- linux,rs485-enabled-at-boot-time: empty property telling to enable the rs485
  feature at boot time. It can be disabled later with proper ioctl.
- rs485-rx-during-tx: empty property that enables the receiving of data even
  whilst sending data.

RS485 example for Atmel USART:
	usart0: serial@fff8c000 {
		compatible = "atmel,at91sam9260-usart";
		reg = <0xfff8c000 0x4000>;
		interrupts = <7>;
		atmel,use-dma-rx;
		atmel,use-dma-tx;
		linux,rs485-enabled-at-boot-time;
		rs485-rts-delay = <0 200>;		// in milliseconds
	};
Commit	Line	Data
0331bbf3 NF	1	* RS485 serial communications
	2
	3	The RTS signal is capable of automatically controlling line direction for
	4	the built-in half-duplex mode.
	5	The properties described hereafter shall be given to a half-duplex capable
	6	UART node.
	7
	8	Required properties:
	9	- rs485-rts-delay: prop-encoded-array <a b> where:
86466036	10	* a is the delay between rts signal and beginning of data sent in milliseconds.
0331bbf3 NF	11	it corresponds to the delay before sending data.
	12	* b is the delay between end of data sent and rts signal in milliseconds
	13	it corresponds to the delay after sending data and actual release of the line.
	14
	15	Optional properties:
	16	- linux,rs485-enabled-at-boot-time: empty property telling to enable the rs485
	17	feature at boot time. It can be disabled later with proper ioctl.
	18	- rs485-rx-during-tx: empty property that enables the receiving of data even
	19	whilst sending data.
	20
	21	RS485 example for Atmel USART:
	22	usart0: serial@fff8c000 {
	23	compatible = "atmel,at91sam9260-usart";
	24	reg = <0xfff8c000 0x4000>;
	25	interrupts = <7>;
	26	atmel,use-dma-rx;
	27	atmel,use-dma-tx;
	28	linux,rs485-enabled-at-boot-time;
	29	rs485-rts-delay = <0 200>; // in milliseconds
	30	};
	31