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DVI daughter card hell.

Honored Contributor II



I was wondering if anyone has had any issues with the receiver side of DVI daughter cards? I'm using a DE3 board with a Stratix III SL150. The daughter card is connected into port C of the board. 


I have already tested and troubleshooted the Terasic DVI daughter card which ended up failing the loopback test. Some of the blue pixel bits were not the right values. I have sent it back for repairs, but in the meantime I am trying out the Bitec DVI daughter card.  


This one is showing a lot of distortion on the display I'm using. For example, if the display is all one colour and I move the mouse cursor onto the screen, it creates distortion at different parts of the same rows that the cursor is moving along.  


Now, I am setting up a loopback test for this Bitec card, which takes a bit longer because all of their demos are only plug and play with the Cyclone III board that they make.  


I was wondering if anyone had any experience with either of these DVI cards and had any advice? 


FYI, the display I'm using can show many different FPGA-generated test patterns without error. In signalTap I can see that all the DVI signals seem to have the right timing. I'm not sure if the wrong type of EDID data would cause the distortion I'm seeing. The port C on the DE3 board passes the test of the HSTC pins.  


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2 Replies
Honored Contributor II



At the advice of Bitec, I changed the voltage supplied to the card. The DE3 board allows you to change the voltage for each of the 4 HSTC ports separately. I changed it to 2.5 V from 3.3 V (which is what the original Terasic card needed).  


The distortion was mostly fixed, but the colours are still all the wrong intensities. 


I have a feeling that I should wait for the Terasic card to be repaired and returned to me.  


Any ideas are still appreciated though.  


Honored Contributor II

I should follow up.  


The support from Bitec was helpful. It would have been nice to have in their documentation the right voltage for the card though. Because there were a large number of things that could have been wrong, it was hard to pin down that problem. The last bug i mentioned before was unrelated to the card. 


It all works now!