ben Posted July 9, 2011 Report Share Posted July 9, 2011 Hi all, I built a homebrewn TV output wing, which could be an interesting replacement for the VGA+jack outputs of the arcade kit. It's a very simple R-2R ladder 6 bit DAC for the video line, and a plain wire for the audio (the DAC must be implemented through logic) You can very easily output B/W video, and colors with some efforts : The schematics : You should use R=115 ohms and 2R=230 ohms to get 0.3V from "010000" (black) on the input and 1.0V from "110000" (white), the remaining "001111" being left for color modulation at high luminance. A picture of the homemade prototype : You can see I used 120 and 240 ohms resistors. That's incorrect, but it only affects slightly luminance and saturation , not hue, so the resulting picture looks fine. I attach some VHDL code, for the PAL encoder and the audio DAC. You should use a 64 MHz clock in the PAL encoder : you could adapt the code for 32MHz, but then you'll get heavy dot crawl. EDIT: phase reversal does work. I just made a stupid mistake in the java program that generated the yuv tables, inverting red and blue... Best, Bentv_output.zip Link to comment Share on other sites More sharing options...
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