On 28/01/2011, at 18:28, Hans Petter Selasky wrote:
> For this kind of applications ISOCHRONOUS transfers should be used. Then you 
> can have a double buffer guard in the range 1-56ms, regardless of the buffer 
> 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. 

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 :)
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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