using a USB video camera

Nov 02, 2003 3 Replies
U

Does anybody have a lead on a low end USB video camera (Creative, Logitech, etc) for which the USB interface data is available ? It's for an embedded system which has a USB controller. I'd like to be able to hook one of those cheap web cams to it and capture the images. The only way to talk to them seems to be via Windows USB drivers and the vendor's drivers and I don't want to use those because this isn't a windows system. Logitech's developers kit is no help.



I'm aware of the CMUCam and that there are drivers for some web cams under Linux. I'm looking for other alternatives if there are any. Something that says if you want to get the image from this camera, do this over the USB connection.


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L

that

It's not as simple as that, though. Many cheap pencams are, for instance, based on the ST STV0680 chip. This is about as simple as it gets, and it's still not simple. USB is inherently non-simple, which is why a GP OS is recommended if you intend to use it. There is no simple "bridge two wires and listen for raw pixel data at 19200bps".

The STV0680 is supported in the Linux kernel directly, here is the page for the specific module:

formatting link
The Linux driver is probably the most concise real-world reference you're going to find (and I fully realize this is damning with faint praise). If you really want an easier method of doing it, you need to use a parallel-interface camera or CMOS sensor module. Even that is not simple.

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J

Cameras are streaming devices what usually work over USB using Isochronous Transfers @12 Mbit what is the most complicated kind of telegram with the USB.

Hope you know the diffrences between a USB device and the USB Host.There is definitely no possibility to connect a camera to anything else than a hub (or root hub with host controller). The host interface is something complete diffrent to the device interface usually included in embedded devices.

You cannot connect 2 USB devices becouse the is no host for enumeration available. To avoid this dis- advantages, there is a new standard what is known as USB on the go with diffrent mechanical connectors but I believe not available for embedded CPU now. Hope you already considered this, otherwhile go and change your plans

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