From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike O'Connor Date: Fri, 17 Mar 2017 03:57:06 +0000 Subject: Re: Setup pppd over rs-485 point-to-point Message-Id: <5d73678b-598e-ee64-fb0a-949e4f229fe1@pineview.net> List-Id: References: <2d19b2f1-bb0f-9a09-6d40-f05388c66af5@gmail.com> In-Reply-To: <2d19b2f1-bb0f-9a09-6d40-f05388c66af5@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ppp@vger.kernel.org On 17/03/2017 1:48 PM, Woody Wu wrote: > Hi, > > I want to setup pppd to connect a Linux laptop to an embedded Linux > device. The Linux box connected to a rs-232 to rs485 converter, then > the convert connected via a two-wire rs-485 cable to the embedded > Linux device's rs-485 port. > This generally will not work as rs-485 is half duplex, the issue is that the switching time between transmit and receive will mean loss of data, how ever RS-422 will work. > On the otherhand, I can make success with similar commands when two > devices connected with rs-232. So I guess, this failure was because > the rs-485 is half-duplex. But I searched google, people seemed say > pppd should work over a point-to-point rs-485 connection. So I want > to get help from your experts. > I've not done any searches but I can not see how it could ever work. PPP is a an async meaning it can transmit and receive at any time. > Thanks in advance. > -woody Mike