Converting RGB to VGA using FPGA

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By retrocanada76

Champion (460)

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22-10-2014, 20:26

Yes, it's possible. See my current project:

https://www.youtube.com/watch?v=lIcOhfh5lVg

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By Fabf

Master (222)

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22-10-2014, 21:34

With scanlines ! great job !
Does it need a big FPGA ?

By retrocanada76

Champion (460)

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22-10-2014, 21:56

Right now it only runs on altera DE0-Nano. Don't know if it will run properly on other FPGAs. I tried compiling for Altera III and I couldn't make the PLL to build.

Probably it will run only on Altera IV chips. It uses 600 LEs + a SDRAM.

By ARTRAG

Enlighted (6244)

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22-10-2014, 22:01

Where can I buy one?

By Sky_hawk

Champion (267)

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22-10-2014, 22:23

Very nice! I would love to do a similar project, to convert rgb and cvbs to HDMI. Yes, very nice indeed Smile

By NYYRIKKI

Enlighted (5382)

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22-10-2014, 22:23

WOW! That looks REALLY interesting...

I would really like to see results of this MSX monitor test program when run trough your converter.

By retrocanada76

Champion (460)

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22-10-2014, 22:49

Wow nice a screen calibration program ? All I needed to adjust it. I will run it when I have time.

By retrocanada76

Champion (460)

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22-10-2014, 22:52

I am not sure how effective it would be to convert CVBS because you need to separate the bands on it. The ADC is very limited on my side, it can only digitize 3-bits, but I digitize R,G and B in parallel.

In the cvbs there is not much you can do, but you can consider it as half-resolution and you could get 4-bits doing 16 comparisons and a 4 resistor R2R DAC. Good luck Smile

By giuseve

Paladin (733)

giuseve's picture

23-10-2014, 07:56

Nice job. If you prefer Scart to HDMI 720/1024 I suggest a LIGAWOO converter. On Amazon at €32 and it works great

By NYYRIKKI

Enlighted (5382)

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23-10-2014, 09:26

retrocanada76 wrote:

a screen calibration program ?

It is not very good tool to calibrate a screen, but it can be used to test the typical effects that usually cause flat screens etc. non CRT devices to fail miserably and also to test some capacitors of CRT screen. Please read the attached HTML documentation to understand what you should see and description of the potential problems.

By maxis

Champion (512)

maxis's picture

23-10-2014, 10:23

retrocanada76 wrote:

I am not sure how effective it would be to convert CVBS because you need to separate the bands on it. The ADC is very limited on my side, it can only digitize 3-bits, but I digitize R,G and B in parallel.

In the cvbs there is not much you can do, but you can consider it as half-resolution and you could get 4-bits doing 16 comparisons and a 4 resistor R2R DAC. Good luck Smile

Hello! Congratulations with the working prototype. I agree with you, digitizing the CVBS is not a trivial task, since without a great quality decoder it brings a little value. End of 90-s I have built a very simple scan rate converter where I was using the triple ADC/triple DAC frontend and discrete PLL to lock on sync. If it could have any help, here is the schematics of it:

Block Diagram:
http://www.wolfa.net/novatec/projects/block.pdf
Schematics Page1:
http://www.wolfa.net/novatec/projects/page1.pdf
Schematics Page2:
http://www.wolfa.net/novatec/projects/page2.pdf
Schematics Page3:
http://www.wolfa.net/novatec/projects/page3.pdf
Schematics Page4:
http://www.wolfa.net/novatec/projects/page4.pdf

As you can see I had a tiny by today standards CPLD(Altera MAX7S128) and a triple 8 bit ADCs and DACs. With a very little signal processing it became very useful, since the signal from MSX was quite noisy. The actual resolution required 7 bits per color to reproduce correctly the full palette + noise.

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