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From: Sam O'Nella on 6 Feb 2005 09:09
Jacek Mazurkiewicz wrote:
> Can anyone give me an idea as to the bare minimum system requirements
> for generating the picture information for some NTSC video at a very
> low resolution?

Anyone remember the Sinclair ZX-80? Good times!


From: Jacek Mazurkiewicz on 6 Feb 2005 12:33
Jacek Mazurkiewicz wrote:

> Can anyone give me an idea as to the bare minimum system requirements for
> generating the picture information for some NTSC video at a very low
> resolution?
>
> I'll be working with a small 8085 microcontroller for which I don't yet
> have the exact specifications (it either operates at a 1KHz or 1MHz clock
> speed), and I was wondering if I could somehow use this to generate a
> composite video signal, or if the microprocessor is underpowered for such
> a
> task. I'd need some auxillary circuitry to generate the video sync
> (possibly using an LM1881). If anyone here who's done something similar
> wouldn't mind giving a few pointers to a newcomer, please post any
> information that you think might be useful to know.
>
> Thanks
> Jacek Mazurkiewicz


Many thanks to everyone who wrote in; your comments were most helpful. I
will post again once I get more details regarding the system and it's
capabilities; I am doing this for a class, so I'm pretty much locked in to
using the particular microcontroller that comes with the system.

I suppose that I needn't overlay my video onto an existing source, so the
LM1881 is out of the picture for me. As far as the type of video I'll be
looking to generate goes, some boxes or characters that I store in ROM
would be just fine; I'm mostly interested in generating the video as a
proof of concept.

I'll be checking out the resources you guys mentioned and hopefully will be
able to come up with a tractable problem.

Thanks Again

Jacek
From: Paul Carpenter on 6 Feb 2005 17:35
On Sunday, in article <v7GdnUgs6tqzuJvfRVn-iA(a)comcast.com>
sonella(a)gmail.com "Sam O'Nella" wrote:

>Jacek Mazurkiewicz wrote:
>> Can anyone give me an idea as to the bare minimum system requirements
>> for generating the picture information for some NTSC video at a very
>> low resolution?
>
>Anyone remember the Sinclair ZX-80? Good times!

To the best of my knowledge the video was controlled by a Ferranti UCLA
(UnCommited Logic Array - FPGA) to drive the timing and shifting out
a section of a line's video data. The memory was dual ported with video
controller becoming bus master (forcibly..) and grabbing the video
data.

The ZX80 did not use the micro to *directly* control timing and data.

As was mentioned in other posts an external controller (CPLD etc..)
is one solution to controlling the video and possibly video data.

--
Paul Carpenter | paul(a)pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/> PC Services
<http://www.gnuh8.org.uk/> GNU H8 & mailing list info
<http://www.badweb.org.uk/> For those web sites you hate

From: Jim Granville on 6 Feb 2005 19:26
Jacek Mazurkiewicz wrote:
> Jacek Mazurkiewicz wrote:
>
>
>>Can anyone give me an idea as to the bare minimum system requirements for
>>generating the picture information for some NTSC video at a very low
>>resolution?
>>
>>I'll be working with a small 8085 microcontroller for which I don't yet
>>have the exact specifications (it either operates at a 1KHz or 1MHz clock
>>speed), and I was wondering if I could somehow use this to generate a
>>composite video signal, or if the microprocessor is underpowered for such
>>a
>>task. I'd need some auxillary circuitry to generate the video sync
>>(possibly using an LM1881). If anyone here who's done something similar
>>wouldn't mind giving a few pointers to a newcomer, please post any
>>information that you think might be useful to know.
>>
>>Thanks
>>Jacek Mazurkiewicz
>
>
>
> Many thanks to everyone who wrote in; your comments were most helpful. I
> will post again once I get more details regarding the system and it's
> capabilities; I am doing this for a class, so I'm pretty much locked in to
> using the particular microcontroller that comes with the system.
>
> I suppose that I needn't overlay my video onto an existing source, so the
> LM1881 is out of the picture for me. As far as the type of video I'll be
> looking to generate goes, some boxes or characters that I store in ROM
> would be just fine; I'm mostly interested in generating the video as a
> proof of concept.
>
> I'll be checking out the resources you guys mentioned and hopefully will be
> able to come up with a tractable problem.

You'll need to generate the Line and Frame Sync pulses, and add in the
Video information, to create a monochrome VBS ( Video,Blanking,Sync)
-commonly IIRC the composite signal is 1V p-p.

One challenge will be to do this, on an 8085, without also getting
time jitter from the software.
Start by trying to generate the Sync, and a simple large square box
in the centre of the screen. That will establish signal levels, and
stability.
-jg


From: Kenneth Lemieux on 7 Feb 2005 06:56
See http://www.8052.com/users/phillipmgallo/ for a good explanation of
generating video using an 8052.

See www.speechchips.com for a cheap, completed solution.

Jacek Mazurkiewicz <jack(a)jessmaz.com> wrote in message news:<gBjNd.3179$wK.468(a)newsread3.news.atl.earthlink.net>...
> Can anyone give me an idea as to the bare minimum system requirements for
> generating the picture information for some NTSC video at a very low
> resolution?
>
> I'll be working with a small 8085 microcontroller for which I don't yet have
> the exact specifications (it either operates at a 1KHz or 1MHz clock
> speed), and I was wondering if I could somehow use this to generate a
> composite video signal, or if the microprocessor is underpowered for such a
> task. I'd need some auxillary circuitry to generate the video sync
> (possibly using an LM1881). If anyone here who's done something similar
> wouldn't mind giving a few pointers to a newcomer, please post any
> information that you think might be useful to know.
>
> Thanks
> Jacek Mazurkiewicz
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