From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Stein Subject: Re: [PATCH] Documentation about RS485 serial communications Date: Tue, 19 Oct 2010 17:27:27 +0200 Message-ID: <201010191727.53314.alexander.stein@systec-electronic.com> References: <20100408111310.524f7354@lxorguk.ukuu.org.uk> <4CBD8EE4.5040808@evidence.eu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: linux-arm-kernel@lists.infradead.org Cc: Grant Edwards , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org List-Id: linux-serial@vger.kernel.org On Tuesday 19 October 2010, 16:29:48 Grant Edwards wrote: > On 2010-10-19, Claudio Scordino wrote: > > +2. HARDWARE-RELATED CONSIDERATIONS > > + > > + Some CPUs (e.g., Atmel AT91) contain a transceiver capable of working > > both + as RS232 and RS485. > > Pardon my curiosity, but I've looked at a few AT91 parts, and I've > never seen on with an internal transceiver -- nor does Google seem > able to find any. > > Frankly, I'd be pretty surprised, since it would be very difficult > (fab-wise), to build a mircoprocessor with I/O cells capable of > withstanding the voltage levels specified in RS232. > > Can you specify to which parts you're referring? I doubt the AT91 do have an internal transceiver but it has a dedicated pin feature (RTS or CTS or something) which can be used to switch between RS232 and RS485 by setting a bit in the USART provided the pin is connected properly. Regards, Alexander