[filmscanners] Re: Off Topic: About those USB flashmemorydrives...

["Bob Shomler" <bobf2@shomler.com>]

>One think I still don't quite understand.  My digital camera, as soon as
>it is attached to the USB port of my computer and turned on, obviously
>communicates with the computer, because the LCD screen of the camera
>reads "Communicating with computer" and the computer launches the
>downloading software, and the download is both sent to the hard drive
>and to a memory resident program, so I can see thumbnails of the images
>on the computer screen.
>
>Would there be no way to make the camera request info off the jump drive
>and then handshake and download the image data to it, or must a CPU be
>controlling the communications back and forth?

Hello Art.  So far as I know there would not be the ability for the camera to 
do what you describe.  What you are seeing with the camera is that when you 
plug it into the USB, that action causes the computer/host side USB interface 
to recognize that there is new hardware on that USB link.  It polls the link, 
discovers that the new HW is known to the system, invokes the device driver 
identified with that camera (that binding established when you installed the 
camera SW) and this driver initiates I/O to the camera to establish 
communication.  It is while this activity and related work is going on that the 
camera puts up the "communicating with computer" message.  So you need 
something with host SW capability (such as "CPU") to initiate the host-side 
activity that establishes the camera-to-computer connection.

Bob Shomler

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