The Rock Pi 4C specs stated the following.
Mini DP to HDMI is not supported. You can only convert Mini DP to DP connector.
Is the reason you can’t convert from DP output to HDMI because the DP output is 2 lanes?
I would like to know why. Please let me know.
I think it’s a driver issue currently but I can not confirm that because DP is splitted from the type C phy, that’s why it’s only 2lanes. Because for USB 3.0 type C, the DP is shared with USB3.0, when DP is 4K@60, USB drops back to 2.0.
I was able to confirm that the miniDP to HDMI conversion can be done correctly as long as it is an active conversion, referring to the following.
https://discuss.96boards.org/t/how-to-configure-display-port-to-hdmi/9133/2
Perhaps it means that you have to be an active convert to be able to display it properly.
Either way, this problem has been solved.
It looks like the solution. We will try to find some “active” DP to HDMI converters.
At first, I also hit the wall with HDMI/DP signal issues on my RockPi4C. All my mini DP to HDMI cables and adapters from my older MBP’s weren’t working and none of my micro HDMI to HDMI cables I pulled out from working RPI4’s weren’t working on 4C either.
I solved these issues by ordering high quality 4K micro HDMI to HDMI cables and an Active Mini DP to HDMI such as:
https://www.amazon.ca/dp/B01FM51O0W/?coliid=I2PM2Q9VJNVTAF&colid=3VRONTTC7L8UB&psc=0&ref_=lv_ov_lig_dp_it