In message , David Pearson (SKYTRONICS) writes >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. I've just tried how fast I can read from my parallel port under Windows 98 SE using a driver DLL, I managed 100,000 reads in 120mS - however, this was just sequential reads, no handshaking or waiting for data to become valid. My machine is a Celeron 667 overclocked at 720MHz using EasyTune III. -- Nigel. /--------------------------------------------------------------\ | Nigel Goodwin | Internet : nigelg@lpilsley.co.uk | | Lower Pilsley | Web Page : http://www.lpilsley.co.uk | | Chesterfield | Official site for Shin Ki and New Spirit | | England | Ju Jitsu | \--------------------------------------------------------------/ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads