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Old 11-12-2003, 06:06 PM
Jan Panteltje
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Default Trying to digitize video with CTT differential input, but webpack wont't cooperate...:-)

OK, now it works, problem with webpack is it so often gives wrong messages,
now it gave a correct on (I was using a pin differently) and I did not
believe a word it said anymore..
So, the 1.4 V pp input video on a CTT pin with 3.3V supply.
A r2r ladder on the comparator reference.
A 8 step successive approximation, that looks at 0 / 1 from the input (video
lower or higher then reference) gives 8 bit video.
Because I only use 1.5 of 3.3V it is now 7 bits.. this can be changed.
First thing was my DVD player, and is in color, even with 50 MHz clock.
But VERY noisy, really bad... plenty of detail RF parts.
But this noise, I think maybe the reference or comparator switch level is
affected by everything else happening in the FPGA?
I test with a second r2r ladder as DA to the output.
Anyways, will try some more later, see if this can be made noise free?
External comparator perhaps?
Will see.
I have biased the CTT at 1.5 V and AC coupled the video in.
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