David,

I'd pass on the USB PIC solution and go with a full speed device
(http://usbsimm.home.att.net) for USB. What is your desired data rate in
bits/sec? Are you trying to make a transfer of video in a closed format to a
custom application, or "regular" video that windows understands?

-Robert Severson
http://usbsimm.home.att.net
http://www.jged.com
http://www.annatechnology.com

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of David Pearson (SKYTRONICS)
> Sent: Thursday, December 28, 2000 11:27 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: PIC data via PC parallel port to screen
>
>
> Hi,
>         Let me clarify the application a bit.  The PIC based
> unit is transmitting
> video from a CCD (a CCD for a astronomical camera) to
> computers that someone
> may already have, a printer port or USB.  The transfer time must be
> minimized to get as fast a frame rate as possible.  The only viable
> alternative to the parallel ports is a full speed USB
> interface.  I've been
> looking at the new PIC micro with USB, but it seems to be a
> low speed USB
> interface suitable for a mouse or keyboard.  The second
> generation unit will
> most likely be full speed USB.  As the project stands now,
> I'm getting a 4
> second transfer via the parallel port.  With the current hardware, A/D
> converter, signal conditioning, the best rate I could expect
> is about 15usec
> per pixel.  Right now I'm getting a little less than 30 usec.
>  The delays
> are now in the bit toggling and reading by the PC from the
> parallel port.
> The frame transfer time of 4 seconds vs 2 seconds is not
> really important
> when capturing the imaged frame ( an extra 2 seconds after a image
> integration time of 10 minutes doesn't matter much), but it
> is important
> when in the focusing mode.  While focusing you need to see
> the image quickly
> as you turn the focus knob.
>
> Again, thanks to you all for your help and suggestions.
>
> Regards,
> Dave
>
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