VGA and PAL output from FPGA

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I'm after a bit of advice on selecting some parts for a 'hobbyist'
project which may eventually turn into a commercial product...

I'm developing a board with an FPGA which will produce RGB digital
output ultimately for display on RGB (15kHz), VGA and PAL/NTSC composite
video. Not necessarily simultaneously - worst case is a different FPGA
image for the former two options.

I've some experience with generating monochrome CVBS and VGA output from
an FPGA, so I believe I have a handle on the technical aspects. But I'd
like to offload much of the work (especially the PAL) to COTS parts, and
this is where I don't have much experience.

First of all, is there a single encoder chip that is capable of
outputing *both* RGB (15kHz and VGA) and PAL/NTSC (again, not
necessarily at the same time)? For example, an RGB->PAL encoder with a
'pass-thru' mode (which basically acts like a video DAC).

Failing that, I'm looking at the Chrontel CH7003 and Averlogic AL100/128
PAL encoders to do half the job. I'm hoping that they are capable of
running in slave mode (they accept the pixel clock) in some funky
resolutions approximating but not equal to 'standard' VGA (horizontal)
resolutions?

I'd complement that with a simple triple video DAC (like the ADV7125
used on the Xilinx dev boards) for RGB (15kHz) and VGA outputs.

In either case/mode, I'd be doing the video timing (except for PAL
output) in the FPGA and so supplying the pixel clock and syncs etc to
the devices (they're slaves). Different FPGA images might run at
different resolutions, some may target 15kHz monitors whilst others may
target VGA, etc, hence the 'flexible' requirements.

As far as my approach to the problem is concerned, am I on the right
track here? Did I choose the best/cheapest/easiest-to-get parts? Or is
there a better/simpler/cheaper way to do it?

Keep in mind that it is only a spare-time project atm and although I'm
willing to make some investment, obviously I'll only be ordering and
manufacturing in very small quantities at this point. At best you could
consider it a 'niche' product so even if I did eventually realise a
commercial product, it would still be low volume.

TIA for any help/hints/suggestions!

Regards,
Mark

Re: VGA and PAL output from FPGA
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CH7003 can do PAL, NTSC and VGA check out the datasheet
its not clear if the VGA mode with CH7003 can accept any format but a lot of
formats are supported so if you are happy with them then CH7003 can do it
all.

or check ADI (www.analog.com) video encoders, they most do either pal/secam
or pure RGB dac

sure make sure you select a component that you actually can purchase, ADI
can send free samples, with Chrontel check availability in sample qty
Antti






Re: VGA and PAL output from FPGA

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Philips do some video encoders that may be worth a look - e.g. SAA7126 I think
there are a few
varients in the range - often used in set-top boxes so should be fairly cheap,
and you may be able
to scavenge some samples from dead boxes.
For VGA, if you only need TV resolution you may be able to do some tricks, e.g.
generating vga sync
while feeding suitably tweaked fake ccir sync to the encoder.

Re: VGA and PAL output from FPGA

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They all seem to be YUV inputs. I haven't considered what that would
require in the FPGA. I understand it's not too difficult to transform
(digital) RGB to YUV? Any comments?

Regards,
Mark

Re: VGA and PAL output from FPGA

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http://elm-chan.org/works/crtc/report.html


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Re: VGA and PAL output from FPGA
On Thu, 13 Oct 2005 20:20:56 +0200, Paul Carpenter  

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hmm Motorola MC1377P for example, its only PAL color encoder, any will do

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Re: VGA and PAL output from FPGA

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Thanks, but it uses the CXA1645, which converts analogue RGB.

I have raw *digital* RGB output from an FPGA, which I want to convert to
analogue RGB (15kHz), VGA, and composite (not necessarily at the same time).

I'm favouring a triple video DAC for RGB & VGA atm (ADVXXX), and encoder
for composite/s-video (like the CH7003), both driven off the FPGA
output. Timing is generated in the FPGA (mainly to enable time-sliced
access to some SRAM, so the pixel clock will be some synchronous
dividend of the main FPGA system clock), and the encoder will be a slave.

Regards,
Mark

Re: VGA and PAL output from FPGA

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sory, I hit reply after reading 2 first lines, my bad :(

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all that comes to my mind is MC1377P, LM1889, TEA2000 (can you say  
dinosaur? 85 was a good year). I did few circuits with the first one and  
they worked reasonably well. But forget about simultaneous PAL/VGA with  
those.


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Re: VGA and PAL output from FPGA

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or just output analog VGA from your pcb and cut development/soldering time  
buying this box
http://www.chipzone.com/shop/showdetl.cfm?DID12%&Product_ID22%9
pinout http://ucon64.sourceforge.net/ucon64misc/conn.html#11
Looks unprofessional, butt ugly, bulky, but only $20 new (free/beer from a  
friend/ebay), tested and works great.
Inside you will find MC13077P, one transistor and RF modulator.

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