6 Replies Latest reply on Aug 21, 2017 11:37 AM by rguevara

    Activate an unidentified HDMI display - manually switching displayport dual-mode to HDMI mode




      I'm trying to activate a display. The display has an HDMI port. I'm using a mDP to HDMI cable. The display works fine when connected to another computer using the same cable. However, the NUC doesn't recognize this display (it does recognize other HDMI displays).


      If before I connect the display, I connect another HDMI monitor which is recognized, I can activate the unrecognized display by issuing the following commands:


      xrandr --newmode 1024x600 48.96  1024 1064 1168 1312  600 601 604 622  -HSync +Vsync

      xrandr --addmode HDMI1 1024x600

      xrandr --output HDMI1 --mode 1024x600


      This "forces" to activate a 1024x600 resolution display, and the display turns on and everything is OK (although xrandr still reports HDMI1 as "disconnected").


      However, if I don't start by connecting an identified monitor, the last command fails with "xrandr: Configure crtc 0 failed" message.


      My guess is that connecting the recognized monitor switches the port from DisplayPort mode to HDMI mode, and then the xrandr activation command works.


      The display should be inside an embedded device, so there's no way to ask the user to first connect a different monitor.


      Is there a way to force the port to switch to HDMI mode? Or, alternatively, is there something I can do to make the NUC recognize the HDMI display?


      I'm using NUC5i5MYBE, Ubuntu 16.04.


      Thank you very much,