nevetsokyeron
Posts: 2
Joined: Mon Jul 15, 2019 11:55 pm

Pi4 - force HDMI to specific framebuffer?

Tue Jul 16, 2019 12:06 am

I have a Pi4 setup with an ssd1322 (128x64) OLED display for it's primary task. It's set to use /dev/fb0.

Now when I plug in an HDMI monitor (to do some debugging from the console), the HDMI wants to take over fb0 and forces the OLED to fb1 - at which point i get console on the OLED and my application on the HDMI.

If I remove the HDMI monitor, the OLED goes back to using fb0.

I tried settingframebuffer_priority=X to 0,1 or 2 with no change. (although I don't fully understand what that parameter is supposed to set).

On the Pi3, HDMI was always fb0, so I could set my OLED to fb1 and forget about it, but now the Pi4 seems to allocate the framebuffer dynamically so it changes depending on what's hooked up(?)

Is there a way to force HDMI to use fb1 instead of fb0?

User avatar
topguy
Posts: 5626
Joined: Tue Oct 09, 2012 11:46 am
Location: Trondheim, Norway

Re: Pi4 - force HDMI to specific framebuffer?

Tue Jul 16, 2019 12:12 am

Is there a way to force HDMI to use fb1 instead of fb0?
Probably easier to force the OLED driver to always choose fb1.

nevetsokyeron
Posts: 2
Joined: Mon Jul 15, 2019 11:55 pm

Re: Pi4 - force HDMI to specific framebuffer?

Tue Jul 16, 2019 5:10 pm

topguy wrote:
Tue Jul 16, 2019 12:12 am
Probably easier to force the OLED driver to always choose fb1.
How exactly would I do that?

If no HDMI devices are in use, the OLED defaults to fb0

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