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jwhendy

Member

Registered: 2010-04-01

Posts: 621

Monitor connected to docking station detected once; then not found

I have an HP 840 G1 laptop which I primarily use with a docking station at work. The docking station is connected to an HP L1945w monitor via VGA. When I first boot or dock my computer, this is what xrandr outputs:

$ xrandr
Screen 0: minimum 8 x 8, current 1366 x 768, maximum 32767 x 32767
eDP1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
   1366x768      60.06*+  40.04  
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP2 connected (normal left inverted right x axis y axis)
   1440x900      59.89 +
   1280x1024     75.02    60.02  
   1280x960      60.00  
   1152x864      75.00  
   1152x720      59.97  
   1024x768      75.08    60.00  
   832x624       74.55  
   800x600       75.00    60.32 
   640x480       75.00    60.00  
   720x400       70.08  
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

I set up the screens such that the external monitor extends to the top of my laptop screen:

$ xrandr --output eDP1 --auto --output DP2 --above eDP1

After a while, I turned off the external monitor:

$ xrandr --output DP2 --off

Now the monitor is nowhere to be found!

$ xrandr
Screen 0: minimum 8 x 8, current 1366 x 768, maximum 32767 x 32767
eDP1 connected primary 1366x768+0+0 (normal left inverted right x axis y axis) 309mm x 173mm
   1366x768      60.06*+  40.04  
   1024x768      60.00  
   800x600       60.32    56.25  
   640x480       59.94  
DP1 disconnected (normal left inverted right x axis y axis)
HDMI1 disconnected (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

After turning off the monitor via xrandr, the status LED on the monitor itself changes from green to orange (going to sleep).
- I've manually powered it of, then turned it on (at which point the LED is green) and run xrandr repeatedly to see if there's a point where it will be "picked up again" with no success.
- I unplugged the VGA adapter from the docking station, ran xrandr, and plugged it back in with no success
- Undocking and docking the computer again does work, but only for the first connect/disconnect cycle; then xrandr doesn't find it again

Any suggestions on how to troubleshoot this and/or keep xrandr aware of my external monitor?

Last edited by jwhendy (2014-06-06 16:22:29)

emeres

Member

Registered: 2013-10-08

Posts: 1,570

Re: Monitor connected to docking station detected once; then not found

Does the docking station have a [brand] name or model, electrical circuitry or controls? From the software side, I would try using a two screen setup (last post, depending on your hardware a slightly different approach might be needed), but I am not sure if this will help.
There might be an electrical circuit between your docking station and its output that triggers this behaviour. However from the hardware side you could try something similar to this. Those are signal voltages, so nothing should go wrong, however as always be careful.

jwhendy

Member

Registered: 2010-04-01

Posts: 621

Re: Monitor connected to docking station detected once; then not found

@emeres: Sorry, yes, it's an HP 2013 UltraSlim Docking Station. I figured it was the only one compatible with the notebook model I provided.

Regarding any electrical circuitry or controls... well, sure, I'm assuming there's some circuitry in there

I'll give a whirl at using that two screen setup when I get a chance. I'm not inclined to think I need to hard-code it in a xorg conf file of some sort given that xrandr finds it just fine. I'm just perplexed by why it goes AWOL after one connect/disconnect. Now that you mention it, it could be the docking station internals, as I'm assuming most folks would be using this to plug in their computer, then completely remove it to go elsewhere, and then come back to their desk. Thus, they'd be physically disconnecting it vs. just toggling?

That said, I'm pretty sure I can use Windows Fn+F4 to toggle laptop vs. laptop + "projector" (what Win7 calls any external display) all day with no issues, so I'd think xrandr should be able to do the same?

Thanks for the input and links.

emeres

Member

Registered: 2013-10-08

Posts: 1,570

Re: Monitor connected to docking station detected once; then not found

Too many variables to be concrete I would argue, could be [not] flushing certain registers, handshake like issues or something really trivial. Maybe asking someone who develops xrandr could help here. Taking measurements on the laptop and dock station output for both gnu/linux and windows would be another option. They probably differ. Does the station get recognized in any way? Do any additional get loaded? Since it has USB ports, at least that should show up (probably as a USB hub).

minus7

Member

Registered: 2013-11-22

Posts: 5

Re: Monitor connected to docking station detected once; then not found

Got pretty much the same issue here (same model), but also with the VGA port on the laptop itself.