composite video output

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Hi everyone

i have a quick question. I am wanting to provide visual feedback to users
for a device of ours through a TV monitor with a composite video input. what
device do i need to look at to create these 'custom screens' is it a video

- Xarion

Re: composite video output
the STV5730 chip does what you need, example here: or here:

Best regards

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Re: composite video output
Hi again!

I see that is what i need. so basicalluy i could use a microcontroller
instead of the parallel port to gernerate the necessary text on the screen?

It says it can use a video input as the background etc...
Is there some way in which i could store an image into a RAM for example and
then encode it into that composite signal? what sort of device would do

- Xarion

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Re: composite video output
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yes, only a serial interface is needed to control the OSD generator, you can
use a microcontroller or even the parallel port of your computer if you want
(and simulate the serial data with bit banging).

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I have no idea about how to easily generate the background except by using
for example a small CPLD connected to a RAM for generating a video signal
with the background you need but you must know PLD programming and add some
more hardware etc... it's according to your skills...

Re: composite video output
Sorry to ask this but what is a CPLD?

- Xarion
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Re: composite video output

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cpld - complex programmable logic device

basically programmable logic blocks connected by a programmable
interconnect(switch matrix)

You can make or design your circuit using either
schematics or a hardware description langauge(vhdl or verilog)
or logic language like abel

The big two programmable logic companies are and

others include
Lattice , Actel, Atmel

xilinx cplds /

Can still get cplds but the largest market share of programmable logic is
fpga - field programmable logic array
a sea of gates or very small blocks again connected by a switch or routing

Can use them for lots of things from custom micro controllers and
controllers , software radio and signal processing , video and
even for prototyping chips. Find them in things like plasma screen tv's ,
mobile phone base stations.

Most of the companies sell cheap starter kits.

xilinx sell their Spartan3 starter kit for US$99

Their spartan3e kit is supposed to be available in september for US$149


Re: composite video output

Xarion schrieb:
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I worked with a module consisting of several chips. This module was able
  to do what you want. But the module needed for the encoding of an
image into the composite signal a RAM large enough for the pixels of the
image, a fast DA converter and the necessary timing logic for the
generation of the pixel clock frequency.

By the way, are you talking about a black and white image, or an RGB
image? RGB would three times more RAM and three DA converters.


Re: composite video output

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Only one D/A converter needed for COMPOSITE color - do the phase
modulation in digital.  Old personal computers handled it pretty well -
just use a pixel clock at four times the color subcarrier, they didn't
even have a D/A converter, they did digital discrete colors by the
pattern of 4 bits corresponding to one period of the color clock.  It's
also debateable if this takes any more memory than monochrome - if you
send the colorburst and thus enable the color decoder in the monitor/TV
you can't have too fine a spatial resolution anyway without introducing
artifact colors.

A single 8-bit D/A converter and a preculculated ram buffer can do a
quite nice job of showing a TV-quality color background, even with the
sync signals generated by the D/A rather than generated externally
(though this does limit the dynamic range available for the picture).

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