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I have a Thinkpad X1 Carbon Gen 7 with Ubuntu 18.04. This devise has one HDMI port and two USB-C port. I want to connect two external monitors on one USB-C port.

When I ran xrandr, I get the following:

eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 309mm x 174mm
   1920x1080     60.05*+  60.01    59.97    59.96    59.93  
   ...
DP-1 disconnected (normal left inverted right x axis y axis)
HDMI-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)

Then I got one of these USB-C adapters with 2-HDMI ports, connected it to the laptop using the USB-C port and connected the two external monitors on the HDMI output of the hub.

The problem is that the two monitors show exactly the same thing, and when I go the Display setting, I only see one monitor. It seems that the two HDMI ports on the hub, are detected as one device.

This same thing happens when I use the other USB-C port. So my question is that if there is a way to have two external monitors using this hub or similar hubs from one USB-C port.

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  • it's like you said, it's a hub (a hub is just something that would duplicate a signal from one source and copy it at all his destination); you re looking on something like a switch, but i don't know if it exist for HDMI (I think it would be really ugly) – damadam Oct 15 '19 at 13:59
  • Thanks, so a hub with 2 HDMI ports can just do mirroring? I though it can actually handle two monitors independently... – SaTa Oct 15 '19 at 14:02
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The Link's fine print says only Windows supports the Multi-Stream Transport (MST) required to daisy chain two monitors. As such I suspect that is why monitors are mirrored.

Check with vendor perhaps there is a work around or it's not too late to return it and get your eighty bucks back.

2
  • Thanks! This makes sense. So Ubuntu does not support MST? Or is it hub specific? – SaTa Oct 16 '19 at 12:45
  • I would shop around for a different hub that supports two with extended desktop. Off the top of my head I can't recommend one. – WinEunuuchs2Unix Oct 16 '19 at 17:20
0

Looks like a dock may (repeat, may) solve your problem: Lenovo advertises multiple docks, but this one explicitly says it supports two external monitors. I would confirm that with Lenovo Support before buying, though.

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