Re: Embedded Linux and PCI (over AT91?)

cs_posting@xxxxxxxxxxx wrote:
On Dec 28, 4:50 pm, bill.valo...@xxxxxxxxx wrote:

For example, the on-chip USB 2.0 is only
full-speed, which may be too slow for a video stream

I thought 'full speed' applied to USB 1 / 1.1 and that 2.0 devices had
to be able to go faster than that?

No. USB 2.0 is just a standard. It supports low, full and high speed devices. The USB 1.1 standard, on the other hand only supports low and full speed devices.

To comply with the USB 2.0 standard, a device only needs a couple more descriptors.

Assuming you are writing compressed video data, USB full speed
probably is fast enough for most purposes. If I recall correctly USB
full speed is 12 mbit/second minus overhead, wheras the official limit
for DVD's is a little under 10 mbit/second. But if you can't do good
compression before writing it you might have to go faster.

The overhead on USB is quite big. I don't think you can get 10 Mbps effective throughput on a full speed device, even if you completely saturate the bus.


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