Hi, > 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? I believe it is neither common nor a good thing. Dynamically switching between electrical levels means that the remote device must be capable of handling both electrical levels, else it might be damaged (i.e., when the serial card is configured to RS485 but switches to RS232 when reset). Or, different pins must be used for RS232 and RS485 (then software switching is not really useful). Jean-Pierre Tosoni > -----Original Message----- > From: linux-serial-owner@xxxxxxxxxxxxxxx > [mailto:linux-serial-owner@xxxxxxxxxxxxxxx]On Behalf Of Pavel Machek > Sent: Tuesday, November 16, 2010 3:30 PM > To: Claudio Scordino > Cc: Greg KH; Nicolas Ferre; linux-serial@xxxxxxxxxxxxxxx; > Grant Edwards; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; Alan > Cox > Subject: Re: [PATCH] Documentation about RS485 serial communications > > > 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? > > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) > http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html > -- > To unsubscribe from this list: send the line "unsubscribe > linux-serial" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
