From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick Menschel Subject: Re: [RFC] K-Line protocol via SocketCAN Date: Sun, 22 May 2016 22:27:32 +0200 Message-ID: <57421634.5050607@posteo.de> References: <573E491E.1000906@denx.de> <573EAE9D.20006@hartkopp.net> <573EFC23.2040906@denx.de> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="------------ms040405040306010901000903" Return-path: Received: from mout01.posteo.de ([185.67.36.65]:37485 "EHLO mout01.posteo.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752493AbcEVU1j (ORCPT ); Sun, 22 May 2016 16:27:39 -0400 Received: from dovecot03.posteo.de (dovecot03.posteo.de [172.16.0.13]) by mout01.posteo.de (Postfix) with ESMTPS id 2789020AE9 for ; Sun, 22 May 2016 22:27:33 +0200 (CEST) In-Reply-To: <573EFC23.2040906@denx.de> Sender: linux-can-owner@vger.kernel.org List-ID: To: Marek Vasut Cc: "linux-can@vger.kernel.org" This is a cryptographically signed message in MIME format. --------------ms040405040306010901000903 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: quoted-printable >> I remember a K-Line implementation for Linux where we had a MPC5200 UA= RT >> which we programmed with bit-banging of some control line to do the >> 5bit/s opening pattern. >> After that we went to 10400 bit/s and did some K-Line communication. >> All this was done by a user space application on /dev/ttyS0. >=20 > Yes, and this does make perfect sense until you start dealing with > faster modes and need more precise timing. The K-Line is limited by > 250kBaud/s bus speed. >=20 Hello Marek, Afaik there is no ECU left that actually needs the "5 Baud INIT". Most ECUs use the "FAST INIT" procedure, means 25ms low, 25ms high, then start communication with 10400Baud. The nasty part are the 25ms low, 25ms high , that is also prior to the 5 Baud Init pattern. After that, everything on the K-Line is pure serial communication. I've done a few test myself with an FT232RL based KKL-Interface and these 25ms low, 25ms high are very hard to realize. No Success at my end.= =46rom my point of view, the 25ms low, 25ms high are the only reason to move into kernel space and possibly switch the Tx Pin to GPIO and pull it low/high for 25ms, then switch it back to UART. 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