If we go on with these less scientific user experiences… As one may guess diy soldering hardly ever helps. But I did that, and luckily, it did not reduce my rock pi 4c totally useless. Now, the new symptoms are as follows; If the hdmi-cable-connector is “suitably” connected to the display, its display wakes up and I can log on. But if the cable or the connector is even slightly touched or disturbed the hdmi-signal is lost (forever) and the board is not, to my understanding, re-sending any hdmi-signals once it has lost its connection to the display. Whatever I do, after getting the blank screen, with the cable (-plugging in-out, twisting, pressing the connector…), the screen is not waking up. So all remains black and nothing visible. To get the screen back I’ve to switch the board off & on - reboot- and then I’ve an hdmi connection working (provided that it woke up if it woke up…, and the cable is not touched/disturbed after initial success). So it’s pretty sensible with the cable/connector set up.
And another thing, although not much related to HDMI/mDP; while playing with bluetooth headphones I could not get any reasonably good sound quality out of those, just stuttering, and a badly lagging bluetooth keyboard / Logitech k270. With the similar set up I’ve the other sbc working well…
Rock Pi 4c mDP no video
Unfortunately, this has also been my previous experience.
BT Audio is an absolute disaster on the 4B and C. Disconnections and / or stuttering without end.
I love the RockPi 4 series but unfortunately it still has some teething problems.
Unfortunately, I still can’t say anything about the X series because I’ve been waiting for the promised delivery since the end of November but it doesn’t come and the Radxa contact person no longer reacts to my questions.
BT audio disconnected/stuttering issues are not related to RockPi4 B/C only but to all RK3399 boards using broadcom AP6256 BT/WIFI chipset. I have exactly those same issues on my RockPro64 boards.
There has been some workaround made for OrangePi4 boards at armbian forums which also use AP6256 but it’s not completely solved yet:
I confirm that the mini HDMI connector is not well soldered. If I touch it the screen turns off. So I am searching to use mDP. The problem remains for me on the NVME boot. It seems to be impossible. Only Manjaro remains at the second boot and I don’t know why at the second boot Debian (Radxa one) doesn’t start.
Ah. Remember that only mDP ACTIVE can work! There must be a chip that talk to the HDMI devices. The board can not send signals to HDMI devices through the mDP port. So only active adapters!