The NEW Build Your Own Arcade Controls
Main => Raspberry Pi & Dev Board => Topic started by: txgraeme on September 06, 2016, 11:48:42 pm
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I just wanted to share my experiences using the vga666 adapter to output native 240p video to an analog TV. I am using an older sony profeel with 34 pin microcomputer (RGB) input. The combination seems to work fine if you can manage to align the TV sync and pixel clock issues. The RPi has a strange limit to its lower frequency pixel clock values in that it has to be a value of 19.2 Mhz ÷ n, where 'n' is an integer value. This gives an option for 240-ish lines, but I still haven't got a good one working for 480i resolution.
Hers's my config.txt lines:
dtoverlay=vga666
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2 #2 for custom DMT
dpi_mode=87 #87 is custom timing below
hdmi_timings= 320 1 16 8 72 240 1 8 5 9 0 0 0 60 0 6400000 1 #320x240 CGA monitor for progressive scan
And here's an example of image produced, I hope it helps someone who was looking for a solution that does not involve a scan converter or interlaced video.
(https://farm9.staticflickr.com/8293/29418959845_7b30b39cd7_b.jpg)
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I plan to work on this over the winter.
My goal is to take 240p from RPI and get it into an SDTV via component inputs for a cabinet project.
I've got an extron VGA off ebay for $12 and a SCART-RGB to YpBPr converter.
Should be able to get it working with one or both of those.
I think.
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I haven't tried to get 15khz into a YpBpR input yet, but am planning to work on that soon for another TV. I hear that a J-Rok (http://www.jrok.com/hardware/RGBv4/index.html (http://www.jrok.com/hardware/RGBv4/index.html)) is a good way to do it as there is no scan conversion taking place, only a colorspace transcoding with sync combiner. I hear it's similar to RGB in image quality, so should be a good option.
I ordered an extron unit a while back from ebay but it was DOA, wish I had the chance to see what it looked like though. It's my understanding that the extron is only necessary if you need a scan conversion (VGA 31khz to RGB 15khz), so you could skip that part if you are already getting 240p direct from the RPi. Eliminating that may help simplify your daisy chain.
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That's correct.
I bought the scan converter before people figured out 240p with the gert board.
I think i just need to read this thread on using SCART to hook my RPI up to the scart to component convertor.
http://forum.arcadecontrols.com/index.php/topic,77370.0.html (http://forum.arcadecontrols.com/index.php/topic,77370.0.html)
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There's a project going on at the moment where someone's got 240p working via a HDMI to VGA converter which is accepting the same modeline from the first post, and passing it along to the RGB out.
http://www.aussiearcade.com/showthread.php/67986-JAMMA-board-from-Raspberry-PI (http://www.aussiearcade.com/showthread.php/67986-JAMMA-board-from-Raspberry-PI)
The project then amplifies the lines as needed and plugs in to a JAMMA connector. I've got a couple of gert vga666 units, but I'm also keen to try these HDMI to RGB as well as HDMI to YPbPr converters (oddly enough the cheaper the converter, the better, as they tend not to do any scaling at all) and see how they all compare.
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Excellent news, thanks for the heads up. This sounds like a good option, I'm going to look into it further.