On Thu, Jul 14, 2016 at 12:44:19AM -0500, Sam O'nella wrote: > I haven't built or marketed anything myself but i believe if i understood > correctly from several folks who have that vga was a cheaper choice due to > licensing costs for dvi or hdmi at the time.
Parts of DVI are patented, but there are royalty-free licences available. It's also fairly like that the patents have all bit expired, or are invalid. HDMI can be treated as DVI with a different plug. I doubt supporting either interface would be a problem on licensing grounds. If nothing else, these things aren't made in high enough volume to attract the attention of the attack lawyers. > Not sure if vga is past that point or open but when keeping home brew kits > cheap for us hobbyists every dollar counts. This is the more likely reason: DVI and related standards use TMDS signalling which requires a reasonably complex logic block running at a minimum of 250MHz to scramble and multiplex the 24 bit RGB into the four output signals. This is not impossible on low-end FPGAs, but it does eat enough LEs that the designer may decide to just support VGA rather than cut back functionality elsewhere or require a more expensive FPGA.
