1280x800 resolution on Chalkboard Electronics 7" screen

I’ve got one of the Chalkboard Electronics 7" touchscreens that I’d like to use with my Jetson TK1. It works, but not at full resolution (1280x800). The best I can do is 1280x720. It looks like a number of others have tried this, but so far I haven’t seen any complete successes.

  • https://devtalk.nvidia.com/default/topic/803701 ("Nothing" works)
  • https://devtalk.nvidia.com/default/topic/800294 (Couldn't get 1280x800, then borked the display settings trying to fix it. Resolved, but not with 1280x800)
  • https://devtalk.nvidia.com/default/topic/803392 (Display wasn't coming up for ~90 seconds, later couldn't get anything to display at all. Resolved, but not with 1280x800)
  • In my case, the EDID information is correct (I flashed the latest firmware, and the resolution option shows up), and the display works at full resolution using HDMI from my desktop (NVIDIA GT 640). But on the Jetson, the screen goes black when I try to select that resolution. I get the follwing output from dmesg:

    [ 1456.109989] tegradc tegradc.1: nominal-pclk:82176000 parent:244000000 div:3.0 pclk:81333333 81354240~89571840
    [ 1456.109992] tegradc tegradc.1: pclk out of range!
    [ 1456.117856] tegradc tegradc.1: nominal-pclk:82176000 parent:244000000 div:3.0 pclk:81333333 81354240~89571840
    [ 1456.117859] tegradc tegradc.1: pclk out of range!
    

    It seems that somehow the Jetson can’t display 1280x800, or maybe that the pixel clock is wrong somehow. I am not sure where to continue debugging this. Any clues, or log files I should be looking at?

    Thanks!

    Hi Steven,

    Tegra HDMI driver supports 480p, 720p and 1080p by default.

    From the log, it is related incorrect pclk. The pclk is not in expected range (81354240 to 89571840).

    I am investigating the solution now.

    Thanks

    It seems that somehow the Jetson can’t display 1280x800

    Officially Tegra BSP only supports a subset of CEA modes necessary for HDMI certification. Tegra devices conform to HDMI.

    Resolution 1280x800 is NOT in the subset of CEA modes.
    https://en.wikipedia.org/wiki/Extended_Display_Identification_Data#CEA-861-E

    If that mode is not a CEA mode then we do not support Audio.

    That is the reason why you see resolution 1280x720.