From owner-freebsd-usb@FreeBSD.ORG Thu Feb 3 06:56:41 2011 Return-Path: Delivered-To: freebsd-usb@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B48521065672 for ; Thu, 3 Feb 2011 06:56:41 +0000 (UTC) (envelope-from doconnor@gsoft.com.au) Received: from cain.gsoft.com.au (cain.gsoft.com.au [203.31.81.10]) by mx1.freebsd.org (Postfix) with ESMTP id 37B9C8FC12 for ; Thu, 3 Feb 2011 06:56:40 +0000 (UTC) Received: from ur.gsoft.com.au (Ur.gsoft.com.au [203.31.81.44]) (authenticated bits=0) by cain.gsoft.com.au (8.14.4/8.14.3) with ESMTP id p136uP8W041912 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=NO); Thu, 3 Feb 2011 17:26:28 +1030 (CST) (envelope-from doconnor@gsoft.com.au) Mime-Version: 1.0 (Apple Message framework v1082) Content-Type: text/plain; charset=us-ascii From: "Daniel O'Connor" In-Reply-To: <201101280858.05077.hselasky@c2i.net> Date: Thu, 3 Feb 2011 17:26:25 +1030 Content-Transfer-Encoding: quoted-printable Message-Id: <0F80A010-B97C-4D05-B604-5EF4B07EF248@gsoft.com.au> References: <9CF6C32F-E230-446B-94FC-C57F0F02B0E4@gsoft.com.au> <201101221433.23194.hselasky@c2i.net> <6AD22899-0B00-483D-A01E-786029A82C9F@gsoft.com.au> <201101280858.05077.hselasky@c2i.net> To: Hans Petter Selasky X-Mailer: Apple Mail (2.1082) X-Spam-Score: -2.51 () ALL_TRUSTED,BAYES_00,T_RP_MATCHES_RCVD X-Scanned-By: MIMEDefang 2.67 on 203.31.81.10 Cc: freebsd-usb@freebsd.org Subject: Re: libusb performance on 8.1 X-BeenThere: freebsd-usb@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: FreeBSD support for USB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 Feb 2011 06:56:41 -0000 On 28/01/2011, at 18:28, Hans Petter Selasky wrote: > For this kind of applications ISOCHRONOUS transfers should be used. = Then you=20 > can have a double buffer guard in the range 1-56ms, regardless of the = buffer=20 > size the hardware uses. That sounds nice :) I am trying to get it working at the moment, however I'm only finding it = capable of 4 or 8 Mb/sec (512 or 1024 byte EP), although perhaps I don't = understand how to do ISO transfer properly. BTW do you have a feel for the latency in bulk vs iso? I currently have = 5-10 msec of buffering in the hardware which I plan on increasing but = I'm not sure what a reasonable amount would be :) I put a logic analyser on my board and it shows fairly regular requests = from the hardware (16kbyte bursts every 2msec or so) however I see = glitches occasionally - 5.5ms, 7.5ms.=20 I am not sure if they are attributable to userland scheduling (in which = case writing a kernel driver should help) or some subtlety in USB = itself. Thanks :) =20 -- Daniel O'Connor software and network engineer for Genesis Software - http://www.gsoft.com.au "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C