piclist 2000\12\09\034029a >
Thread: SCENIX VIDEO VIRTUAL PERIPHERAL Design Challenge and Co ntest
face BY : Nikolai Golovchenko email (remove spam text)

Thanks Mike for the circuit.

I assembled it and now it works in my TV. :) By the way,
this is where I experiment with the SX video thing. The TV
is assembled from a black-and-white monitor and a radio
channel block from a TV. The block has a video output with a
DC component of a few volts (about 2V - I didn't measure
it), but the monitor works only for zero DC video signal.
Before I used a 'dirtier' circuit of a 22 uF capacitor and
an adjustable 470 Ohm resistor in parallel, connected
between video ouput of the block and video input of the
monitor to lower the DC offset. It sort of worked, with
some of contrast lost. Now it's much better with the new
circuit :)

One catch with the DC separator is that the capacitor is
charged by the transistor through the video output and the
output has to have a sufficiently low impedance, which my
radio channel hadn't. So I added a p-n-p emitter follower
before the DC separator to make it work.

It should also work for the SX comparator input (or simply a
digital input) if the transistor base is adjusted to
something like 0.7V. I'll check it.

Yesterday I tried a circuit that separates sync signal from
video. It uses 2 transistors and a few resistors and
capacitors. It has a good digital output, but I still can't
make SX synchronize at the same period to every individual
HSYNC pulse in the noise presence. So besides sync
separation a PLL scheme should be added. In that case, I
guess the sync separation can be made in software
altogether, if the DC separator and a comparator is used.

Thanks all for replies,


---- Original Message ----
From: Michael Rigby-Jones <spam_OUTmrjonesspamEraseMENORTELNETWORKS.COM>
Sent: Friday, December 08, 2000 10:29:13
 To: TakeThisOuTPICLIST@spam@spamspam_OUTMITVMA.MIT.EDU
Subj: [sx]: SCENIX VIDEO VIRTUAL PERIPHERAL Design Challenge and Co              ntest

>> {Original Message removed}
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In reply to: <0F60BEDDC090D41185D300508BCFA39E0AF91F@zpgty002.europe.nortel.com>
See also: www.piclist.com/techref/ubicom/lib/io/index.htm?key=video
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Subject (change) SCENIX VIDEO VIRTUAL PERIPHERAL Design Challenge and Co ntest

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