[PATCH] Documentation about RS485 serial communications

[Pavel Machek]

Hi!

> Documentation about RS485 serial communications

I have seen hardware (kontron pmc-6l) that was capable of switching
between RS232, RS485 and one other standard by software.

Is such hw common? If so, should we have standard interface?

> +   From user-level, RS485 configuration can be get/set using the previous
> +   ioctls. For instance, to set RS485 you can use the following code:
> +
> +	#include <linux/serial.h>
> +
> +	/* Driver-specific ioctls: */
> +	#define TIOCGRS485      0x542E
> +	#define TIOCSRS485      0x542F
> +
> +	/* Open your specific device (e.g., /dev/mydevice): */
> +	int fd = open ("/dev/mydevice", O_RDWR);
> +	if (fd < 0) {
> +		/* Error handling. See errno. */
> +	}
> +
> +	struct serial_rs485 rs485conf;
> +
> +	/* Set RS485 mode: */
> +	rs485conf.flags |= SER_RS485_ENABLED;

IOW... is this supposed to switch electrical levels?

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