XESS Boards have had built-in VGA interfaces since 1997 (and I stole the idea from others who were doing it before that). But the new XuLA FPGA board doesn't have any extraneous parts (just an FPGA, SDRAM, configuration flash and a USB interface), so how do you display graphics with it?
A simple VGA interface can be built on a breadboard with some resistors and a connector. The red, green and blue VGA signals are each driven by a simple DAC like the one shown below. Each color input presents a 75-ohm load to the DAC. The DAC resistors combine with the load resistor to divide the 3.3V digital logic outputs so the total stays below the maximum 0.7V expected by the VGA input. A set of five resistors that scale upwards by a factor of two will implement a single five-bit, 32-level DAC, so fifteen resistors are needed to drive the RGB inputs to create a total of 32 x 32 x 32 = 32,768 colors. <<more...>>
Welcome to my first blog entry for XESS Corp. Ever. For over twenty years I never had a company blog, but now I see the need for a channel to post about ongoing projects and upcoming events. And I'll also meander down other paths of discourse. <<more...>>