Hello
Using BT81x @ 72MHz system clock, it is possible to achieve 30Hz refresh rate for a 1366x768 display, less than the standard 60Hz.
In case the display supports Adaptive Frame Rate(AFR) operation, then it’s possible to get 60Hz refresh rate by set REG_PCLK=1. If AFR is not supported (for LVDS display), the display list shall be less complicated, similar to the performance achieved by our 10” HD demo at Electronica 2018 (1280x800 60Hz).
The EVE series of ICs do not include a frame buffer, they dynamically clock out each computed pixel on the screen. A displays size and what the Pixel Clock is running at will determine the achievable performance. It is also worth noting using larger displays reduces the computational time available for each pixel on the screen.
If we take the example from the following WQVGA settings:
// WQVGA display parameters
lcdWidth = 800; // Active width of LCD display
lcdHeight = 480; // Active height of LCD display
lcdHcycle = 928; // Total number of clocks per line
lcdHoffset = 88; // Start of active line
lcdHsync0 = 0; // Start of horizontal sync pulse
lcdHsync1 = 48; // End of horizontal sync pulse
lcdVcycle = 525; // Total number of lines per screen
lcdVoffset = 32; // Start of active screen
lcdVsync0 = 0; // Start of vertical sync pulse
lcdVsync1 = 3; // End of vertical sync pulse
lcdPclk = 2; // Pixel Clock
lcdSwizzle = 0; // Define RGB output pins
lcdPclkpol = 1; // Define active edge of PCLK
HCYCLE = 928
VCYCLE = 525
VCYCLE * HCYCLE = 487,200
Note: REG_PCLK is using the value 2 which will divide the clock down to 30Mhz.
Result = 30,000,000/487,200 = ~ 61 fps
Best Regards,
FTDI Community