From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cliff Brake Subject: Re: rt application question with rs232 communication Date: Mon, 16 Mar 2009 16:05:15 -0400 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: rt-users To: Leon Woestenberg Return-path: Received: from rv-out-0506.google.com ([209.85.198.229]:17753 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753444AbZCPUFS convert rfc822-to-8bit (ORCPT ); Mon, 16 Mar 2009 16:05:18 -0400 Received: by rv-out-0506.google.com with SMTP id g9so2204515rvb.5 for ; Mon, 16 Mar 2009 13:05:15 -0700 (PDT) In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Sat, Mar 14, 2009 at 10:07 PM, Leon Woestenberg wrote: > Hello Cliff, > > On Tue, Mar 10, 2009 at 1:44 PM, Cliff Brake = wrote: >> Clarification, I don't have the RT patch applied, just CONFIG_PREEMP= T >> from Linus's kernel. =A0Reviewing my notes from several years ago, I= ran >> into a similar issue and the RT patch fixed it, so now to figure out >> the best way to get a recent RT patched ARM kernel ... >> >>> timing. =A0However, it seems that the system has trouble receiving = the >>> response in a timely fashion. =A0I often observe that it takes at l= east >>> 10ms for the application to receive the response data after the dat= a >>> has appeared on the rs232 bus. =A0Is the RT patch something that wo= uld > > We are running a real-time RS-485 protocol where the time window is 1 > ms and only under heavy load we got deadline misses > 1 ms. > Unfortunately I didn't measure the max latency then, but 10 ms sounds > like excessive latency to me. > > Under 2.6.24.7-rt24 (or whatever -rtxy in that series) we have never > missed the 1 ms deadline. Thanks Leon. I guess its pretty obvious at this point I need the RT patch. Still trying to figure out the best way to get this with 2.6.27 or later -- I really don't want to go back to 2.6.26. Thanks, Cliff --=20 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Cliff Brake http://bec-systems.com -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html