AVR-Chat

On Mon, 11 Jun 2007 02:48:22 -0000
 "kernels_nz" <kernels@slingshot.co.nz> wrote:
> Hi guys, I have a curly one, any creative suggestions
> would be
> appreciated.
> 
> Im interested in digitzing a B/W video waveform from a
> standard CMOS
> security camera, im only really interested in one line of
> video but
> the conversion time of the average AVR A2D is around
> 13-50us but the
> whole video frame is around 50us. 
> 
> I know I can overclock the AVR A2D to around 1MHz, but
> that still
> would only give 4 conversions per video frame.
> 
> So, a few ways that I could see around the problem is:
> 
> 1. Faster external ADC -> Not ideal because it adds cost,
> componets
> and it's hard to get hold of Megasample ADCs. Also,
> having a fast
> external ADC is useless unless you can communicate with
> it at super speed.
> 
> 2. Slow down "time" somehow so that I buffer a frame of
> video
> "somehow" and convert it at my leasure using the inbuilt
> ADC. <- This
> method requires "magic" and im not sure what type ? maybe
> someone has
> come across some way of doing this ?
> 
> 3. Use some of the "line" cameras that allow me to clock
> the video
> data out pixel by pixel. <- I can do this, and we even
> have the
> cameras available @ work, but I would prefer to use a
> off-the-shelf
> cheap video camera.
> 
> Any other ideas?
> 
> Thanks !
> 
> Hein B
> Auckland, New Zealand.
> 

No, one video line is about 64us (very close to same for
NTSC and PAL).

Philips (now NXP) makes a whole bunch of video ditizer ICs.
They are very nice and do the synchronizing, etc for you.
You would need a video sync detector for any digitizer
solution.

The simplest, by far, would be a line sensor, I think.
Within limits you can clock it at any rate you want. 

Jim


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