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embedded video?

B

Bob Stephens

Jan 1, 1970
0
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
 
S

Steve at fivetrees

Jan 1, 1970
0
Bob Stephens said:
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.

Maybe look for OSD (on-screen display) devices.

Steve
http://www.fivetrees.com
http://www.sfdesign.co.uk
 
C

CBFalconer

Jan 1, 1970
0
Bob said:
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.

No you're not (dreaming). They used to exist. Whether they still
do is another matter. Look for things to handle menus on TV
screens, etc.
 
J

jim granville

Jan 1, 1970
0
Bob said:
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.

We can get close, with a VGA-232 product, but unfortunately this
outputs PC-VGA video, not NTSC. (ie plugs into a std VGA monitor)
PAL/NTSC give poorer text quality, but do have a place where you need
to overlay (character insert) text onto pictures. In this case, you need
to genlock the character generator to the picture sync.
-jg
 
B

Bob Stephens

Jan 1, 1970
0
We can get close, with a VGA-232 product, but unfortunately this
outputs PC-VGA video, not NTSC. (ie plugs into a std VGA monitor)
PAL/NTSC give poorer text quality, but do have a place where you need
to overlay (character insert) text onto pictures. In this case, you need
to genlock the character generator to the picture sync.
-jg

Well, it gets worse. When I said NTSC I was actually fudging a bit. I need
to generate non standard RS 170 with a sync pulse amplitude of 0.75 V +/-
0.25V and a 3.0V peak video signal.

Bob
 
B

Bob Stephens

Jan 1, 1970
0
Build a video generator out of a PIC (they're cheap) and feed it
parallel data. I've seen seveal listings of how to make NTSC character
video.

Viola! Now you have a cheap video character ic!

Yes, I've downloaded a couple examples - may end up going that route.

Bob
 
B

Bob Stephens

Jan 1, 1970
0
Also, if you really want to feed it serial, use a PIC16F628 with a
hardware UART built in. You should be able to read incomming data
without losing the NTSC timing.

Another option is to generate Closed Caption signals in the VBI interval
(I've done this). Then just set the TV to show closed captioning. You
dont need to generate NTSC here, just locate the proper VBI line and jam
the codes onto it. Text-over-video, the easy way!

Unfortunately, not an option. This thing is talking to a primary flight
display in a glass cockpit airplane.

Bob
 
L

Luhan Monat

Jan 1, 1970
0
Bob said:
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
Build a video generator out of a PIC (they're cheap) and feed it
parallel data. I've seen seveal listings of how to make NTSC character
video.

Viola! Now you have a cheap video character ic!
 
L

Luhan Monat

Jan 1, 1970
0
Luhan said:
Build a video generator out of a PIC (they're cheap) and feed it
parallel data. I've seen seveal listings of how to make NTSC character
video.

Viola! Now you have a cheap video character ic!
Also, if you really want to feed it serial, use a PIC16F628 with a
hardware UART built in. You should be able to read incomming data
without losing the NTSC timing.

Another option is to generate Closed Caption signals in the VBI interval
(I've done this). Then just set the TV to show closed captioning. You
dont need to generate NTSC here, just locate the proper VBI line and jam
the codes onto it. Text-over-video, the easy way!
 
B

Ben Bradley

Jan 1, 1970
0
In sci.electronics.design, Bob Stephens

What about adding another 8051 to run the video code, and using
serial comm from the original 8051?

<slightly_off_topic>
And while I'm at it, did you explain the costs of "last minute
features"? OTOH, it could be argued that it's our jobs to pull off
these things.

I hesistate to mention this because 1. it's probably not made nor
really useful anymore and 2. it shows my age. :) But... there was the
ubiquitous Motorola 6845 "CRT Controller" chip. I forget how many
products this was used in, but I recall it on the original IBM PC
color card, and probably the IBM PC mono card and original Herculese
mono/graphics card. The Apple ][ used its own TTL DRAM refresh
circuitry to also do video output of RAM, but there was an 80-column
card for the ][ that used the 6845.
Well, it gets worse. When I said NTSC I was actually fudging a bit. I need
to generate non standard RS 170 with a sync pulse amplitude of 0.75 V +/-
0.25V and a 3.0V peak video signal.

That may not be a problem - many things generate the composite
video signal by using summing resistors on digital port outputs, and
you should be able to change the levels by changing resistor values.
 
B

Bob Stephens

Jan 1, 1970
0
What about adding another 8051 to run the video code, and using
serial comm from the original 8051?
I'm considering using a low end PIC - mainly because I have source for a
couple of examples in assembler and don't have time to port them to 8051.
Another problem is that we are running out of real estate on the PCB.
<slightly_off_topic>
And while I'm at it, did you explain the costs of "last minute
features"? OTOH, it could be argued that it's our jobs to pull off
these things.
</>
Yup. That's about the size of it. Fortunately these last few features -
video generation, GPS receiver, Fibre Optic transceivers, MIL 1553
communication, USB 2.0 are all considered trivial by the boss ;)

I hesistate to mention this because 1. it's probably not made nor
really useful anymore and 2. it shows my age. :) But... there was the
ubiquitous Motorola 6845 "CRT Controller" chip. I forget how many
products this was used in, but I recall it on the original IBM PC
color card, and probably the IBM PC mono card and original Herculese
mono/graphics card. The Apple ][ used its own TTL DRAM refresh
circuitry to also do video output of RAM, but there was an 80-column
card for the ][ that used the 6845.

Probably a large-ish through hole device yes? I'll check on it though.
That may not be a problem - many things generate the composite
video signal by using summing resistors on digital port outputs, and
you should be able to change the levels by changing resistor values.

Thanks Ben
 
J

Jan Panteltje

Jan 1, 1970
0
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.
Google SAA5246A_CNV_3.pdf
i2c bus interface, will genlock and add your text 25 lines of 40 chars, color.
can run standalone (PLL mode off), 5V, 27 MHz xtal..
If you need drivers see http://www.home.zonnet.nl/panteltje/xkrs/
for some GPL C code.
JP
 
Q

Quack

Jan 1, 1970
0
You could try the BOB-II, which is a small board (30-pin SIMM) which
can be controlled via serial commands from your uC.

I used one once for video overlay, very easy.
I think its capable of 80x40 ascii or something like that, and cost
about $80 as i recall.

It was very quick and easy to start using, just power, serial line and
video out if you dont want to overlay.

http://www.chip-sources.com/products/..\products\specs\Video Overlay Board.htm


Alex.
 
B

Bob Stephens

Jan 1, 1970
0
You could try the BOB-II, which is a small board (30-pin SIMM) which
can be controlled via serial commands from your uC.

I used one once for video overlay, very easy.
I think its capable of 80x40 ascii or something like that, and cost
about $80 as i recall.

It was very quick and easy to start using, just power, serial line and
video out if you dont want to overlay.

http://www.chip-sources.com/products/..\products\specs\Video Overlay Board.htm


Alex.

I saw their website. Actually the BOB II is "not recommended for new
designs" it has been supplanted by the BOB III. Unfortunately I need a
surface mount solution.


Bob
 
V

Vincent Crabtree

Jan 1, 1970
0
Bob Stephens said:
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.

See http://www.decadenet.com/index.html

Never used them myself. Maybe too expensive for what you are looking for?

Use a Faster 8051?

Thanks, VIncent
 
V

Vincent Himpe

Jan 1, 1970
0
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.
 
W

William

Jan 1, 1970
0
Bob said:
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.

I think you're a good 15 years too late. The proliferation of the PC
and the many video cards used in it has pretty much destroyed the
market for the old character generator chips. If I were to need such a
part today, I would probably grab an FPGA and start coding. Depending
on your needs, it could be a pretty small block, perhaps to fit one of
the less expensice CPLD parts from Cypress, for example.

Bill
 
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