Interesting - which kind of board is that?
It is a custom board I designed myself. You can find it here
if you are interested. It is kind of a mess. It started with a VGA board and then I wanted to upgrade it to HDMI (proposed to do this project for a course at school, so the HDMI board had to be finished quickly). It is also my first serious PCB.
I might make it four layers. Then I can make the board a lot cleaner. It should be possible to order 10 pieces for 50$ from China.
The board shown above has 2 layers as well, and I also noticed that the trace impedance cannot be properly matched for recommended value (100ohm) for HDMI transmitter. I'm in the hope that it won't cause issues with 720p or lower output - 4 layer board would have doubled the price.
I think it will be fine. You kept your traces short. I was able to output 640x480 over a 5m HDMI cable with my board and my traces are a lot longer. One thing I did was put a ground plane around the TMDS pairs. That should make the impedance a bit lower. Unfortunately my board started acting weird at the end of the weekend. I think there is a pin not soldered correctly. I need to push on my board and then sometimes it will give an image again. Hopefully I can fix it this weekend.
Also, if you are interested, check the last post by Calpis here
. It is about adding a PLL to the system to make the input and output frame rate lock onto each other. Not sure if there are external PLLs that would be able to get 9900 / 4471 like precision.
Edit: How do you solder your boards?
Also had a look at the MAX FPGAs. Seems like a very good option. No more external flash needed to hold FPGA program and I read it needs only one power supply instead of three (which is kind of annoying). 10M08 already seems kind of expensive: [url=mouser.com/ProductDetail/Altera-Corporation/10M08SAE144C8GES/?qs=sGAEpiMZZMvoScKlWpK8TPb%252brmUEzdPEXeqzFMf60es%3d]link[/url]. Although I have not checked how these chips compare in terms of LEs and internal memory to Cyclone IV. I guess it can still be worth it if you are short on board space. 5$ EP4CE6 from China is interesting as well though.
How do you save your FPGA program? I see an SD card slot, but I thought you then still need a microcontroller for instance to read out the SD card and program the FPGA.