Lpc2000

All,

Look it is relativly easy to do the micro must sync up with the
horizontal and vertical sync pulses.  Then it is a simple matter of
timming and interrupting the original video with your own.  If you
only wnat white text then you only need one output pin.  Toggle it
high when you want white and low when you want the original video to
pass through.  I know PAL the best and it has been a long time but
I'll try and use the correct numbers.

There are 50 frames a second transmitted but each frame is an
interlace.  So video output is even number scan lines in the frame
then odd numbered scan lines.  A video scan line is 62.5uS including
the sync-pluse.  I think that from memory the total sync pulse width
in 12.5uS this leave 50uS of screen data.  So by dividing this 50uS
into as many sections is you like you get a pixel width.  There are
625 lines in a frame and I think 100 or so of them are take up with
vertial refresh this leaves 525 for display.  So a counter that
countes these lines will provide you with a pixel height.  With all
this info a simple B&W OSD should be possible.  If you want different
collours then you will have to split the video stream into RGB and use
three outputs to toggle each of the colours but you still need to do
the timing of the video frame.

Hope this helps and that my infomation is not too incorrect.  The
video bandwidth of a composite video stream is either 5.5MHz or 6.5MHz
(for pal a least) Toggeleing a pin at 15MHz would be more than fast
enough.  The rest is timming and I'm guessing that if a PIC @ 12MHz
can produce video
http://www.web-ee.com/Schematics/PICTetris/PICTetris.htm &
http://www.brouhaha.com/~eric/pic/picpong.html then a LPC @ 60MHz
should be more than capable of doing the same thing.

Hope this helps,
Rod


--- In lpc2000@yahoogroups.com, Onestone <onestone@b...> wrote:
>
> The very early PICs mostly ran with a 4MHz clock, 1MHz Internal. if 
> low/medium rs OSD is possible on a PIC16C54 then I'm sure that the 4MHz 
> I/O speed of the LPC could only improve on this. Although it doesn't 
> look like that particular app note is around anymore, unless someone
has 
> an old version  or the monster applications handbook.
> 
> Al
> 
> Eric Engler wrote:
> 
> >> I think it might be difficult, given the I/O speed limitation.
> >>
> >>    
> >>
> >
> >That's true. Prior to the new high speed GPIO, most ARM chips could
> >only toggle at a speed under 4 Mhz. The new 2148 can toggle around 15
> >Mhz, but it's still going to be a challenge.
> >
> >Might be wise to get one of the PIC-like devices from Ubicom to do
> >this kind of thing.
> >
> >Eric
> >
> >
> >
> >
> >
> >
> > 
> >Yahoo! Groups Links
> >
> >
> >
> > 
> >
> >
> >
> >
> >  
> >
>