Oyvind Kaurstad wrote:
>
> Hi, all.
>
> I'm planning to make a video capturing device using a PIC
> and a PC parallell port.
>
> What I have is a composite 1 V p-p video signal (monochrome, no color bursts)
> (The signal is CCIR, 50 Hz field frequency, interlaced)
>
> I have a lot of ideas on this, but I would appreciate any input.
>
> What I have been thinking is to use a sync separator (LM 1881 from National
> Semi)
> This chip outputs horizontal sync, vertical sync and odd/even field
 information.
> Giving the PIC these signals will enable it to determine the start of each
> frame and
> also each line.
>
> The problem is that a line lasts only 64 uS, and the video signal therefore
 has
> to be sampled 400 times to get a horizontal resolution of 400 pixels.
> At least this is what I'm aiming for.
> I don't need more than 8 bits resoulution on the sampling, probably less.
>
> Another problem is that I will need some kind of buffering, probably the
> entire frame, since the PC-parallell port is pretty slow.
> Maybe using ripple counters to address some kind of memory will do the
> trick? The PIC would of course control everything.
>
> I'm planning to use (and don't you dare laugh :-))  the 16C84 in this project,
> mostly
> because I don't have a programmer that supports anything else.
> (My programmers are both the PICBlaster and the AN589 type. I've been
> using the PIP-02 software for the PICBlaster and different types of software
 for
> the AN589)
>
> Any suggestions, good ideas etc?
>
> Cheers
>
>  -Oyvind
>
> ==========================================================
> 'Oyvind Kaurstad, R & D Engineer, ABB Flexible Automation'
>
> Email : oyvind.kaurstad@nofac.abb.no
>
> //////// My worlds are colliding! - George Costanza \\\\\\\
> ===========================================================

I think you need buffering the entire frame. If you use DRAM then page
mode is fast enough. It is possible to use the build in memory refresh
counter, but it is more slow than page mode. I suggest that you use two
memory banks, write four times to the first bank (page mode) while you
refresh ( with internal counter ) the other. The timing is more fast than
PIC16C84 handles and you need some external logic or a PLD to do it.
PIC16C84 is fast enough to handle the high column adresses.

Regards,
Jens Dyekjfr Madsen