Messages in this thread | | | From | Ed Vance <> | Subject | RE: RS485 communicatio | Date | Thu, 13 Mar 2003 08:56:26 -0800 |
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On Wed, Mar 12, 2003 at 10:15 PM, linuxppp@indiainfo.com wrote: > Hi all, > am currently working on PPP over serial interface (RS485) in > linux 2.4.2-2. I believe RS485 half duplex system and hence > only one can transmit at a time. And for RS485 we basicaly > use Master-Slave or Primary-Secondary kind of communication. > I don't know how to achieve the same using PPP since i need > to have max of 10 nodes connected via serial interface. I > tested with two nodes using PPP daemon it works fine. > Following are the commands i issued > > In PPP server: > $usr/sbin/pppd -detach crtscts 10.10.10.100:10.10.10.101 > 115200 /dev/ttyS0 & > > In PPP client side : > $/usr/sbin/pppd call ppp-start > where ppp-start file is copied into directory /etc/ppp/peers/ > that had the following > > -detach /dev/ttyS0 115200 crtscts > noauth > > This point to point communication worked fine with RS485 > interface. If i had to connect one more node what i need to > do. Please clarify with the following > > i) Whether the existing pppd takes care of the RS485 with > multi node , if so how do i manage giving commands > ii) If there is no direct support how do i go ahead. Is there > any other layer 2 protocol allows me to acheive TCP/IP > communicattion over RS485 which is my ultimatum. > > I will be grateful if anybody of them could help me with my > current problem. >
I believe Point-to-Point Protocol only supports point-to-point symmetric links. Don't think there is any multi-point support in the protocol. IIRC, PPP also requires a full duplex link, which is not available on an RS-485 link with more than two stations, even if it is a 4-wire link.
I don't know of an easy way around this fundamental limitation.
Maybe somebody on the kernel list has a suggestion.
Cheers
---------------------------------------------------------------- Ed Vance edv (at) macrolink (dot) com Macrolink, Inc. 1500 N. Kellogg Dr Anaheim, CA 92807 ---------------------------------------------------------------- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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