connecting a FP5 handset with DP-Alt support to HB31C3A1CDPPD3 (HB31) and from there by USB-C cable to a 3K USB-C monitor gives here a “No Signal” on the screen. However both, the monitor and the HB31 are powered by 80W and 100W (which is overkill, as the HB31 supports already PD). As the HB31C3A1CDPPD3 features a VIA - VL103 chip, I assumed it can handle a monitor over USB-C. Connecting the USB-C cable directly between handset and USB-C monitor works fine.
My goal is to connect the handset (USB-C) by cable to ethernet (RJ45), mouse (USB-A), keyboard (USB-A) and monitor (USB-C). Is there a reason, it not to operate, as I expected it to work?
Hello @FPDesktop32 and thank you for your interest in our Community.
I would like to confirm that your expectation does indeed mostly match this device (although it has no RJ45 ports, so I assume you are using a USB Network adapter).
Since the monitor works when connected directly to the Fairphone 5, the phone is clearly capable of producing a DP Alt Mode signal. The next step would therefore be to determine whether this is a hardware issue with the hub/cabling or a USB-C/DP Alt Mode interoperability issue with the Fairphone.
A few things I would recommend trying:
Make sure the monitor is connected to the VIDEO OUT USB-C port and not the separate 100W PD-only input on the other side.
Use the same USB-C cable between the hub and monitor that works when the monitor is connected directly to the phone.
Connect the hub’s power adapter (if you are using any) and monitor first, then connect the hub to the Fairphone.
Try restarting the Fairphone while the powered hub and monitor are already connected.
Make sure the Fairphone 5 is running the latest available software (there are known DP Alt Mode issues fixed by the Fairphone’s August software update).
Important (if possible) → test the HB31C3A1CDPPD3 and USB-C monitor with another USB-C video source (laptop/computer etc.) that supports DP Alt Mode.
If the monitor works through the HB31C3A1CDPPD3 with another DP Alt Mode host, that would strongly suggest that the hub itself is operating normally and that the issue is related to USB-C/DisplayPort negotiation with the Fairphone 5.
It would also be useful to know whether the Ethernet, keyboard and mouse are detected by the Fairphone through the hub while the monitor shows “No Signal.” That would help us determine whether only the DisplayPort Alt Mode negotiation is failing or whether the entire USB-C connection is affected.
Sorry for the confusion. The adapter is called 10G2A1C25EPD.
Thanks for your precise reply. The bought adapter has already a RJ45 port and the mentioned VIA - VL103 chip.
The Fairphone5 uses keybord, mouse and cable internet just fine, while the No Signal is shown on the 3K HDR display.
Should I adapt the title line to the correct adapter?
I hope this helps better understand the situation and available solutions. Please let me know if you have any further questions and have an excellent day!