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PICList Thread
'Video Frame Grabber'
1995\11\30@095807 by Dana Frank Raymond

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Has anyone seen an inexpensive design for a frame grabber? I need to design
one for BW video camera use (RS170 base band video).

This project will most probably use a PIC 16C64/65/74 uP.

Thanks.
Regards, Dana Frank Raymond
spam_OUTdfrTakeThisOuTspamicom.ca

1995\11\30@125718 by Luigi Rizzo

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> Has anyone seen an inexpensive design for a frame grabber? I need to design
> one for BW video camera use (RS170 base band video).

I doubt you are going to make it with a PIC. Much easier if you have a
cheap DSP, such as some members of the 21xx family.

       Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: .....luigiKILLspamspam@spam@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================

1995\11\30@195751 by Chris Elmquist

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>
> > Has anyone seen an inexpensive design for a frame grabber? I need to design
> > one for BW video camera use (RS170 base band video).
>
> I doubt you are going to make it with a PIC. Much easier if you have a
> cheap DSP, such as some members of the 21xx family.

Although, if you look way back in some issues of Byte Magazine...
Ciarcia did a thing he called ImageWise which was a frame-grabber
based on an 8031 running at 11+ MHz.  It was able to grab the frame
in one frame time and then crank it out a serial port at 57.6Kbaud.

I would think that PICs (which run leaner and meaner than 8031's)
would be able to do this task.

There are also some products which hook to a PC parallel port and
can grab a "frame" after several passes of full rate video have
gone by.  This is a bummer if your image is not relatively static
but OK for something like a security camera or some such. Unfortunately,
I can't think of any published designs for one of these "cheapo"
circuits.  Anyone else ?

Chris

--
Chris Elmquist, N0JCF
chrisespamKILLspamn0jcf.com
.....n0jcfKILLspamspam.....amsat.org

1995\11\30@201704 by Mike Keitz

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>There are also some products which hook to a PC parallel port and
>can grab a "frame" after several passes of full rate video have
>gone by.  This is a bummer if your image is not relatively static
>but OK for something like a security camera or some such. Unfortunately,
>I can't think of any published designs for one of these "cheapo"
>circuits.  Anyone else ?

These are composed of a standard slow ADC with a sample-and-hold at the
input.  The sample and hold is triggered by a delayed horizontal sync pulse.
As each frame comes in, the grabber takes and digitizes typically one sample
from each line.  (i.e. the samples form a vertical line down the picture).
The delay is adjusted for the next frame (field if not interlaced) so the
samples are taken one pixel later, so for a given horizontal resolution of n
pixels, n frames of video are required.  This works out to about 8 seconds
for a 512 x 256 image (for the "el cheapo" system, interlace isn't used; the
two fields are used interchangeably, giving a picture repetition rate of 60
Hz rather than 30)  The ADC on a PIC 16C71 is probably suitable for this.
It may even be fast enough to take two samples per line, sampling the whole
picture in 4 seconds.

One or several PIC chips could do most of the timing functions in a
full-rate frame grabber, (maybe not the lowest few bits of the address
pointer) as well as interface to the ultimate destination for the data.  Of
course, a fairly large external RAM is required, and for full rate a fast
ADC as well, in addition to the usual sync extraction and synchronization.

It's suprising no one has asked how to grab video in *color* yet.

-Mike

1995\11\30@203402 by Ben Raymond

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>
> There are also some products which hook to a PC parallel port and
> can grab a "frame" after several passes of full rate video have
> gone by.  This is a bummer if your image is not relatively static
> but OK for something like a security camera or some such. Unfortunately,
> I can't think of any published designs for one of these "cheapo"
> circuits.  Anyone else ?
>

Electronics World and Wireless World published just such a circuit a
couple of months back. I don't have the issue handy, I can check the
issue number if anyone is interested.

Ben Raymond
EraseMEbraymondspam_OUTspamTakeThisOuTeleceng.adelaide.edu.au


'Video Frame Grabber'
1995\12\01@030408 by Luigi Rizzo
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> > > Has anyone seen an inexpensive design for a frame grabber? I need to
design
> > > one for BW video camera use (RS170 base band video).
> >
> > I doubt you are going to make it with a PIC. Much easier if you have a
> > cheap DSP, such as some members of the 21xx family.
>
> Although, if you look way back in some issues of Byte Magazine...
> Ciarcia did a thing he called ImageWise which was a frame-grabber
> based on an 8031 running at 11+ MHz.  It was able to grab the frame
> in one frame time and then crank it out a serial port at 57.6Kbaud.

how much external logic ? With a 21xx you can even do the refresh of
your DRAM in software, and you only need the DSP, the flash ADC, RAM,
EPROM, and *maybe* a single PAL or a few gates to generate the
chipselect for the various devices. With a PIC or other
microcontroller, I guess you can save the ROM, but not the RAM, but the
sampling/address generation is probably going to be controlled by
external circuitry.

Anyways, I'd like a few more details about the circuit you mention.

       Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigispamspam_OUTiet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================

1995\12\01@092519 by Kevin Krauel

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Chris Elmquist wrote:

>There are also some products which hook to a PC parallel port and
>can grab a "frame" after several passes of full rate video have
>gone by.  This is a bummer if your image is not relatively static
>but OK for something like a security camera or some such. Unfortunately,
>I can't think of any published designs for one of these "cheapo"
>circuits.  Anyone else ?

I think the circuit design that is thoroughly described in the book,
"Practical Image Processing in C", fits the above description.  This book
was written by Craig A. Lindley, and was published in 1991 by John Wiley
and Sons.

       -Kevin.

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