Mark McClelland wrote:
> sting sting wrote:
>
>> Hello ,
>>
>> Did anybody try to test a webcam when running with sl811 USB Host Controller ?
>>
>> Is this Host Controller not too low in speed for a webcam
>> (whuch usually grabbs 25 fps by default?)
>>
>> Did he succeed ? in case he did - with which camera and driver?
>
>
>
> It's possible... the person who submitted the sl811 driver successfully tested it with an OV511+ camera. The reason why most cameras don't work is that the SL811 has a tiny buffer. I don't remember the usable exact size, but it's something <= 256 bytes (approximately 180, I think).
>
> Any isochronous-based camera controller with alternate settings for MxPS < 180 should work. This includes OV511+, OV518, OV518+ and probably others. Check the descriptors at http://www.qbik.ch/usb/devices/ to be certain. Of course the driver needs to support alternate selection (ov511 does, with the "packetsize" module parameter).
>
> I'm guessing that cameras that use bulk transfers should work fine, as long as they can handle a throughput that's 1/6 of normal. Some don't, notably the Orange, Trust, and Aplux USB 2.0 cameras when in full-speed mode.
SL811 has no buffer and o FIFO in hardware!
All buffer are implement in HCD driver. The buffer is exact 240 Bytes and can only store one frame.
The access to SL811 have 256 registers, they are 16 controls and 240 datas. This 240 bytes is also the limit for transfer of a frame. (You asks last time.)
Henry
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