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ADV7511W Video Troubleshooting

Question asked by dennisjm on Mar 14, 2014
Latest reply on Jun 27, 2014 by DaveD

I'm attempting to drive the ADV7511W with an FPGA.  I'm not getting video on the output TV though so I thought I'd see if anyone has some suggestions for debugging that I may not have thought of.  Here are a few data points.

 

* HDP 0x42[6] goes high

* sense 0x42[5] does not go high.  I'm not sure if this pertains to the issue or not.  I confirm voltage on the Txc+/- pins that they are being pulled up to 3.3V when the cable is plugged in.

* I can read the EDID fine.  Edid confirms the supported video modes that the TV advertises to support.  I'm attempting to drive 720p@60hz.

* pll locked

* I'm using the video generator based on AN-1270 to simulate video.  I'm driving clk_in close to (but not exactly) 74.25 Mhz. 

* with on Oscilloscope, I can see Vsync, hsync and DE signals at the expected frequency.

* used register settings from AN-1270 to  program the ADV7511W.

 

After all that, I can't seem to get the TV to display anything.  One thing I noticed is that if I probe the clock pins on the HDMI cable sometimes the change in capacitance causes some error in the clock.  At that point the TV will go black for a moment as if it's attempting to sync a signal but then go back to the default no-signal screen.  Could it be that the clock signal isn't closely matched enough to the sink expectations?  Perhaps there is some other bigger problem.  I'm new to HDMI though so I'm not sure if I'm looking at the correct things to find what the problem is.

 

Thanks for any input.

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