From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Edwards Subject: Re: RS485 implementation questions (primarly in atmel_serial.c) Date: Thu, 31 Jan 2013 14:42:03 +0000 (UTC) Message-ID: References: <000401cdfef7$0d4a9020$27dfb060$@acksys.fr> Return-path: Received: from plane.gmane.org ([80.91.229.3]:60850 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751851Ab3AaOmR (ORCPT ); Thu, 31 Jan 2013 09:42:17 -0500 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1U0vLV-0003li-Cn for linux-serial@vger.kernel.org; Thu, 31 Jan 2013 15:42:33 +0100 Received: from dsl.comtrol.com ([64.122.56.22]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 31 Jan 2013 15:42:33 +0100 Received: from grant.b.edwards by dsl.comtrol.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 31 Jan 2013 15:42:33 +0100 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org On 2013-01-30, Jean-Pierre Tosoni wrote: > > Well, you need to ascertain that the previous frame is all out AND > the RTS has dropped before sending a new frame. Else the receiver > might think it is the same long frame. Using TXEMPTY interrupt avoids > setting an extra timer. However in the real life you are half-duplex > and never send two frames in a row without waiting for an answer. > Other than that I agree with your remark. > >> rare. But this function is not especially related to RS485. It is >> also applicable in RS232 mode. So in my view it is not the > > True, it applies to some half-duplex RS232 radio modems too AFAIK. It applies to half duplex modems and line-drivers whether they're radio or not. Believe it or not, Bell-202 half-duplex over plain old copper wire is still used a lot in the process control industry. But, because of the general brokeness of both Windows and Linux serial drivers when it comes to half-duplex communications, many of the Bell-202 modems sold these days have automatic tx data detection and handle the "RTS toggle" function themselves. -- Grant Edwards grant.b.edwards Yow! Psychoanalysis?? at I thought this was a nude gmail.com rap session!!!