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  • Writer's pictureMike Chi

Where's the COMP2RGB?

I thought I'd give an update on the COMP2RGB project, the component to RGB transcoder. When I started this project, I thought it was going to be a breeze: follow the LMH1251 datasheet to the dot, add a sync stripper, output buffer and we're good to go right?


Aside from flipping the CVBS and audio pins on the SCART (SHART) connector, the production samples appeared to work beautifully. The LHM1251 even took care of removing the sync signals from the output lines. This is great, because I was about to implement a discrete one from some TI high speed, limiting opamp.


Unfortunately, as with many engineering projects, simple things are never as straightforward as they look and black-boxes often have undesirable behavior that is difficult to assess and correct.


Thanks to Dave Kircher ( https://twitter.com/DirkSwizzler), we discovered an issue with the LM1251 where rapid resolution switches from 1080i back to SDTV resolution cause the LMH1251 sync processing and stripping circuits to enter a weird state. This wouldn't be a problem for normal consumer video applications, but it appears that at least on the PS2 (GT4), the resolution switches fast enough to trick the chip.


Long story short, now implementing a supervisor circuit to manually power cycle the LMH1251 upon switches between HDTV and SDTV signals. Fingers crossed and stay tuned!


In the meantime, enjoy the RGB2COMP :)



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sudundrum
Nov 17, 2019

Would there be much more difficulty in adding a VGA output as well? Maybe not as an additional output on the device but as a passive pin adapter that will enable 31khz RGBHV. Assuming that can be put through a scart connector.

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Mark fons
Nov 16, 2019

I want to enjoy Rgb2comp, buy is out of stock. When is it back?

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ricklewis519
Nov 15, 2019

Damn. I was hoping you he update was that it’s ready to go. Oh well. I can be patient. I love your work, thank you so much.

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Vladislav
Nov 15, 2019

Hi Mike! Can't wait for COMP2RGB. Love what you are doing :) From what I understand it's not easy to make such converter so hope everything turns out well and we'll see COMP2RGB converter soon

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