USB HOST

[Michiel]

Hi,


I want to connect a webcame to a Virtex II pro and do some real time
processing on it. Can someone give me some tips how to use a Virtex II
pro as an USB host?


Greets
Mich

 

[Noway2]

The quick answer to your question is, don't waste your time. You can
buy a USB host controller chip for less than $10. The host controller
chips will either use parallel I/O or DMA transfer, which you can use
to interface to your Virtex chip.

If you wish to implement your own controller, I would suggest that you
start with the USB specification and the specifications for either
"Universal Host Controller" or "Open Host Controller", which are the
two standards. the UHC is easier to implement in hardware but requires
a rmore complex software interface where the reverse is true of the
OHC. For a webcam application, you will also require control transfers
and probably isochronous transfers as the protocols you need to
support.

On top of all of this, there is a lot of work regarding the physical
interface to the USB device. The physical interface involves overload
detection, controlled impedances on a differential transmission, and
noise protection circuitry. The USB specification will provide the
requirments that you need to follow.

For more information I would suggest checking out the website:
www.lvr.com.

 

[Michiel]

Tanx for the answer

can you tell me with is a good USB host controller chip?

greets
Mich

 

[Noway2]

I have used the isp1161A1 by Philips, though it was about 1.5 years ago
that I selected the chip. I am not certain as to what is out there
today, but I would have to say that the selection has undoubtedly
improved. I believe there is now a ISP1181 that is probablly a 'high
speed' usb controller.

The webpage link that I provided (www.lvr.com) has a section dedicated
to embedded USB, including discussions about the different host and
device controllers. You should be able to get a good overview there.

I would recommend using an Open Host Controller as they are much
simpler to interface to. The one I used has 16 data lines, 1 address
line, read and write strobe, and the physical USB signals at a cost of
about $6.