FPGA Central

Hi,

I have built a dvi to lvds converter. However the picture still flickers
and is off by 1 pixel. I think I am having trouble with the vsync. Is
the vsync on the tmds line the same as on the analog port? Does anybody
know if the vsync just does one pulse per frame, I think so but I am not
sure...

In my EDID Data I find this:
V Active Lines 1024 <-this is okay
V Blank 42 <- what does this mean?
V Sync Offset 1 <- offset to what?
V Sync Width 3 <- I guess it means that my pulse is 3 lines?
V Image Size

Thanks,
Benjamin

Hi,

I figured out that my VSYNC is negativ polarity, although my EDID says
its positiv....
It know also that it's only one pulse per frame.

The other questions are still open.

regards,
Benjamin

Benjamin Menküc wrote:
> Hi,
>
> I have built a dvi to lvds converter. However the picture still flickers
> and is off by 1 pixel. I think I am having trouble with the vsync. Is
> the vsync on the tmds line the same as on the analog port? Does anybody
> know if the vsync just does one pulse per frame, I think so but I am not
> sure...

VSync is one pulse per field, which is to say one pulse per frame in a
non-interlaced image.

> In my EDID Data I find this:
> V Active Lines 1024 <-this is okay

Should be obvious; you'll display 1024 active lines.

> V Blank 42 <- what does this mean?

Vblank means "how many lines are part of the vertical blanking time."

> V Sync Offset 1 <- offset to what?

This means, "The line, relative to the start of the vertical blanking
time, on which we assert the vertical sync pulse." This is always
confusing, depending on whether you consider the first line to be line
One or line Zero, but I suspect this means that your vertical sync
pulse begins at the start of the vertical blanking time.

> V Sync Width 3 <- I guess it means that my pulse is 3 lines?

This tells you the width of the vertical sync pulse, given in units of
lines. So, yes, this means that your VSYNC will be active for three
line times.

> V Image Size

This should be the total image size, which is the sum of the number of
active lines and the number of blanked lines.

-a

Hi Andy,

my vsync period would be 1066 then. So the vsync has no front-porch but
a lot back-porch, okay.

Maybe I will try to verify it with an oszilloscope some time.

Thanks for Your answer.

regards,
Benjamin