Board not booting if HDMI display connected during powerup


Hi everyone,

I am trying to hook the up board into a Picade arcade cabinet. It comes with a 1024x768 LCD panel and a HDMI-to-LVDS board, meaning that the display is driven by HDMI.

In order to set up the board, I plugged it on my desktop 1080p HDMI display and everything was going as expected. I could see the Up board logo at startup, navigate through the BIOS menus, etc. But after moving the board and plugging it to the cabinet's panel, it was not visible on the network. It is only after restarting it without the panel plugged in that it finally booted normally.

This behavior of the board not booting up only happens if this particular panel is plugged and powered on during the first ~3 seconds of the boot process. My best guess is that the BIOS detects the panel and tries to do something with it, but something goes wrong (maybe because of the resolution?) and it remains stuck there. But if the panel becomes visible when Linux starts, it has no problem picking it up.

I have updated the firmware to UPC1DM11, but that did not improve things. I am also thinking of wiring a serial connection to see if I can get more information about what is going wrong from the BIOS.

Potential workarounds that I am considering:

  • Adding a time-delay circuit that waits ~3 seconds after power is applied to power the panel,
  • Replacing the HDMI-to-LVDS board with another one, maybe eDP-to-LVDS?

But of course, it would be nice to get things working as they should. Would anyone have ideas of how I could debug/fix this issue?

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