I’ve reported a USB hub auto-selection bug to the Support team, but wanted to mention it here in case anyone else has similar issues.
Problem Setup
I have the following devices connected to the Spectrum:
- MacBook Pro, using a single 40Gbps USB-C cable for video, USB data and power delivery. Spectrum is in refresh rate priority mode.
- Windows laptop with eGPU. DisplayPort cable is connected to the GPU in the eGPU case. USB-B cable is connected to the laptop.
Both the video source and USB hub source settings are set to automatic selection.
What Actually Happens
Automatic hub source selection is inconsistent.
Scenario 1:
- MacBook is connected, powered on.
- Windows laptop is turned off and disconnected from both eGPU and USB-B.
- eGPU is still connected via the DP cable, but is not powered on.
The Spectrum correctly uses the USB-C connection for both video and USB hub source.
Scenario 2:
- MacBook had been running but is sent to sleep. It remains connected to the USB-C cable.
- Windows laptop is connected to eGPU and USB-B and is turned on.
- eGPU case is connected via the DP cable and powers on with the laptop.
The Spectrum correctly uses the DP connection for video, but continues to use USB-C for the hub source. If the OSD is used to reselect automatic selection, it appears to restart the selection process and the USB-B connection is used.
Scenario 3:
- MacBook is disconnected, but the USB-C cable remains plugged in.
- Windows laptop is connected to eGPU and USB-B and is turned on.
- eGPU case is connected via the DP cable and powers on with the laptop.
The Spectrum correctly uses the DP connection for video. It refuses to automatically change to USB-B as the hub source, even when using the OSD to reselect automatic selection. Hub source has to be manually changed to USB-B.
Note: I don’t think that the eGPU case has any specific impact on the problem. It will likely still occur when using a standard PC that gets turned on/off but remains connected.
What’s Expected To Happen
The USB hub changes automatically depending on the video input.
- When the USB-C connection is selected for video, it should also be used for the USB hub source.
- When the DisplayPort connection is selected for video, the USB-B port should be used as the USB hub source.
- Automatic hub selection should work regardless of whether the video source is selected manually or automatically.
Alternatively, it should be possible to set a USB hub source for each video input. When the video input changes (either automatically or manually), the associated hub source is used.
