I need to generate simple NTSC composite video text as a last minute
feature on an 8051 based embedded project. I have found some software
examples but they really chew up CPU time. Does anyone know of a one
chip solution for generating black and white video? I'm picturing
something like a "video UART" which you could spit ascii characters at
and let it generate the composite video, sync etc. I'm probably
dreaming.
TIA
Bob
Philips has an 8051 with OSD on board specifically for monitors. but
possible it genlocks on the RGB signal.
ST also makes this
another option is to code on in a differnt 8051.
Check out the 8051 make by CYGNAL.
www.cygnal. they have some variants that
run 100 mips ! i use these frequently.
I had plans of making a similar device to what you need
use a LM1881 as sync separator.
That way you get Horizondal and vertical sync.
Hook these two into INT0 and INT0
I use the built in ram to make a pixel map ( the cygnal has a lot of ram up
to 8192 Kbyte ) So you could even create 'pages'
Vertical sync resets my 2 'scan' counters.
using timer 0 i increment one of the conters that scans the pixelmap
When Horizontal sync happens the line counter increments and the pixel
counter is reset.
The pixeldata is avaialble on port pin. it controls controls an 4066 analog
switch that interrupts the incoming vieo , and second 4066 switch toggles
between balck and white levels ( preset with stupid resistors.
That way i can overlay textlines where i want. since i use a pixelmap i van
even make drawings.
My signals are thus synced with incoming video and 'ride' on the existing
signal.
This was the idea. i did some calculations and using a 25 mhz clocked
Cygnal i could do a 20 charakter a line 8 line display without problems.
( 128 pixels by 64 pixel equivalent of an LCD graphic display )
I never built it though.