Electronics > FPGA

FPGA VGA Controller for 8-bit computer

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nockieboy:
Eek.  Been so busy recently.  Have been pottering about with the graphics tile demo/game I started ages ago this evening and managed to take some pictures of these blue lines/artefacts that occasionally appear on screen - they'll fade in, flicker about, the pattern might change (as shown in the pics) and they'll disappear again.  I've tried cable-wiggling as my most serious attempt to debug the issue, but now I have photographic evidence thought I'd post here to see if there's an HDL or FPGA cause for this issue?

 

BrianHG:
If the issue is with a too long or bad HDMI cable, then there is nothing you can do in firmware to fix.
(IE: if plugging and unplugging the cable or changing a HDMI cable, switching to a different monitor input changes the garbage pattern, then the issue is not in the firmware) \

(Note that my LG Flatron24 did this on the red channel when I used the HDMI input and the DECA board.  Switching to the DVI input using a HDMI-DVI adapter fixed the issue,)


Otherwise, we need to look at your compiler build's timing report.

If timing isn't met for the VGA output clock section, maybe just changing the compiler optimization technique will fix the issue.

Or, maybe, I need to invert the VGA output dac clock, or set the DVI encoder's CLK input phase using it's I2C controls.

nockieboy:
Okay, no worries, when I get a moment I'll plug it into my TV in the living room and see if the lines appear there.  It's only a 1-metre HDMI cable, but points taken about the cable quality etc.

Any follow-up on the FPU thread at all?  Is that implementation okay or are there issues?

BrianHG:

--- Quote from: nockieboy on December 09, 2022, 10:19:33 pm ---Okay, no worries, when I get a moment I'll plug it into my TV in the living room and see if the lines appear there.  It's only a 1-metre HDMI cable, but points taken about the cable quality etc.

Any follow-up on the FPU thread at all?  Is that implementation okay or are there issues?

--- End quote ---
The FPU implementation is up to you.

Did you fix the video blue speckles?

nockieboy:

--- Quote from: BrianHG on December 14, 2022, 06:15:25 am ---Did you fix the video blue speckles?
--- End quote ---

I think it must be interference on the HDMI cable somewhere, I've re-routed the cable and it hasn't come back since, but I've not had any long periods of time to test for it recently, so I'll hold fire on calling it fixed just yet.

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