I wasn't going to go for the HDMI output right away. I was just going to build a 4-bit VGA interface on the GPIOs to start.
The other issue that concerns me a little is the audio CODEC chip on the Cyclone V GX board is different than the DE1 board. I am hoping to just disable the audio at first until I can get a very minimal system working.
The SSM2603 audio codec on the C5G board is register compatible with the WM8731 found on the DE1.
It has a few extra registers to control some extra functionality, but they power up to sane defaults.
Audio code should just work without modification.
If you are feeling lazy, you can always get one of these for the video out:http://www.wayengineer.com/index.php?ma ... M84JW-GNhE
Compatible with the C5G, 8 bits per colour, gives you basically the same video out as a DE2 board.
Wire the 4 bits per colour coming out of the minimig code to the top 4 input bits of the ADV7125.
I have one, they give a pretty sharp output.