Date: Thu, 3 Feb 2011 20:54:23 +1030 From: "Daniel O'Connor" <doconnor@gsoft.com.au> To: Hans Petter Selasky <hselasky@c2i.net> Cc: freebsd-usb@freebsd.org Subject: Re: libusb performance on 8.1 Message-ID: <4DAFAF80-746B-4272-86CC-BB284E59D4F6@gsoft.com.au> In-Reply-To: <201102030822.49266.hselasky@c2i.net> References: <9CF6C32F-E230-446B-94FC-C57F0F02B0E4@gsoft.com.au> <201101280858.05077.hselasky@c2i.net> <0F80A010-B97C-4D05-B604-5EF4B07EF248@gsoft.com.au> <201102030822.49266.hselasky@c2i.net>
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On 03/02/2011, at 17:52, Hans Petter Selasky wrote: >> 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. >=20 > Hi, >=20 > You need to set the multiplier to 2 or 3. Then you get 3*1024 bytes at=20= > maximum. OK, so I need.. usb_xf[i].xf =3D libusb_alloc_transfer(3); p =3D malloc(3 * 1024); libusb_fill_iso_transfer(usb_xf[i].xf, h, 0x82 p, 3 * 1024, 3, usbcb, = &usb_xf[i], 2000); ? >> 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 :) >>=20 >> 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. >=20 > Are you using two isochronous transfers or just one? It is a single in endpoint. The device also has 2 in bulk and 2 out bulk = endpoints for other data but they are idle while the iso one is running. -- 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
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