Messages in this thread | | | From | Grant Edwards <> | Subject | Re: [PATCH] Documentation about RS485 serial communications | Date | Tue, 16 Nov 2010 18:03:43 +0000 (UTC) |
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On 2010-11-16, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote: > On Tue, 16 Nov 2010 10:13:22 -0600 > Matt Schulte <matts@commtech-fastcom.com> wrote: > >> On Tue, Nov 16, 2010 at 8:30 AM, Pavel Machek <pavel@ucw.cz> wrote: >> > 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? >> >> In my opinion this type of card is not that common. Generally >> speaking the achievable baud rates for this type of multi-protocol >> card are very limited because of limitations of the transceiver chips. >> It seems that most of the time people would rather have a faster >> serial port than one that does several different voltages > > If there are two types in common use then thats enough to say we should > have a common interface IMHO
Comtrol, Moxa, B&B, Sealevel, and others all sell PCI cards and Ethernet attached serial ports that have selectable interfaces (typically RS-232/422/485). Comtrol and Moxa have had drivers in the kernel tree for ages, but they've always had to use custom ioctl calls for things like configuring 232/485/422 mode and half/full-duplex mode.
There are also tons of small Linux-based industrial server appliances from Comtrol, Silex, Digi, Moxa, and others that have selectable interface serial ports.
Having a standard API for things like interface mode, half-full duplex, inter-character timeout, 9-bit mode, and so on would be life a lot easier for those of us who maintain Linux serial drivers...
-- Grant Edwards grant.b.edwards Yow! I always have fun at because I'm out of my gmail.com mind!!!
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