adammw
Posts: 21
Joined: Fri Jun 15, 2012 4:28 am

HDMI/DVI Output can't be re-enabled after turned off

Fri Jun 15, 2012 4:59 am

Disclaimer: This post is both troubleshooting and programming - not sure which section to put it in.
I'm trying to experiment with the vc_tvservice APIs and the tvservice binary provided itself, and I've noticed that when you turn the screen off and on again like so:

Code: Select all

/opt/vc/bin/tvservice -o
/opt/vc/bin/tvservice -p
That when the monitor is turned back on by the last command, the console does not re-appear and you are left at a blank screen with an invisible console (it is still there though, you can execute other commands, just not see them). I've also tried running some of the OpenMax? (OMX) demos such as hello_triangle which displays a black cube with no textures either - very odd. Accessing video on the display is okay though without glitches, omxplayer looks quite good infact without the console behind it.
How can you get the console to re-appear after turning it on, and what is the proper way of making it disappear for example for playing videos?
Thanks

hexameron
Posts: 47
Joined: Sun Jan 08, 2012 12:14 pm

Re: HDMI/DVI Output can't be re-enabled after turned off

Fri Jun 15, 2012 8:00 am

I don`t know why you would want to "turn off" the framebuffer. It is hidden behind any Videocore graphics, so you would not normally see it. It is amusing to find the line in hello_triangle that sets the background colour and make that transparent. You can make the textures transparent as well.

There are a number of interesting bugs in hello_triangle. The textures are loaded at run-time, and it will not throw an error if it cannot find them, so you will need to copy them "somewhere".

bredman
Posts: 1415
Joined: Tue Jan 17, 2012 2:38 pm

Re: HDMI/DVI Output can't be re-enabled after turned off

Fri Jun 15, 2012 8:23 am

It looks like you need to refresh the framebuffer after enabling the display.

This is just a guess.

dom
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5748
Joined: Wed Aug 17, 2011 7:41 pm
Location: Cambridge

Re: HDMI/DVI Output can't be re-enabled after turned off

Fri Jun 15, 2012 8:36 am

bredman wrote:It looks like you need to refresh the framebuffer after enabling the display.

This is just a guess.
Yes, I believe a fbset will bring it back.
(note: you will need to change size/depth of fb or it will be ignored, so try changing to, say 16x16 then back to original resolution.)

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