Incompatible with 4k TVs

[flaviut]

This isn't really a surprise with how the cheap breakout boards are designed, but this system doesn't work with a 4k HDMI signal. The highest quality I was able to get a connection at was 1080/60Hz.

It is possible to create a custom PCB that does handle this properly, and I might at some point. But in the meanwhile, can you update the readme to indicate compatibility so that others know before starting on the project?

[gkoh]

@flaviut Agreed, this isn't really surprising, however I have multiple units that I can confirm work at 3840x2160p@50Hz.
I have not tested all of them, although the quality of the breakout fabrication varies quite significantly.
Some are very clean and high quality units, while others are most definitely not.

Nevertheless, I will add the warning that support for 4K output is not assured.

[gkoh]

Caution added to README, reopening for the custom PCB PR.

[flaviut]

the quality of the breakout fabrication varies quite significantly

It's not really the quality of a specific board as much as the PCB design in general. When you get up to these high data rates, not all wires are equivalent. Not all fiberglass boards are equivalent! There's a very specific way that the board must be designed to be 100% reliable, and there are many ways to mess this up. So for the HDMI data lines, I had to add a ground plane, plug my numbers into the PCB calculator, and make sure all the data lines were exactly the same length.

I'm not an expert and I have a lot of trouble understanding it myself, so I'm probably not doing a good job explaining it.

[ZehCastro]

I was able to get 4K@60 on the 1st try and 4K@60 + HDR on the second, but on both the image would show a few random green pixels.

Makes me wonder if somehow tapping directly on the cable's wires would help alleviate these issues, since most wires would be left "intact".
Cutting the cable's shielding to tap the wires might just make things worse thou.

And perhaps one could just tap the connector of the GPU directly? Definitely not for the faint of heart.
PS: Please don't blame me for dead GPUs. XD

[flaviut]

Makes me wonder if somehow tapping directly on the cable's wires would help alleviate these issues, since most wires would be left "intact".

I'd expect this to work fine, although you'd want to make sure you haven't broken totally through the shielding.

The reason I haven't tried it is because the wires are going to be thin and very annoying to work with. It's fun for the challenge, but I don't think it's practical

[waweic]

If I understood correctly, there isn't really a need to use the passthrough feature at all. On the TV, all CEC pins should be electrically connected