VGA and LCD in mirror mode


So I would really like some information about a project I’m working on.

I am actually on a Colibri iMX6DL with an Aster carrier board and I’d like to display my Qt app on 2 display (VGA and LCD in mirror mode) so the user could use the 7’’ capacitive display or simply plug an external display with a mouse to use it like a normal computer. I have already managed to display on both display at the same time with this vidargs setting.

setenv vidargs ‘video=mxcfb0:dev=lcd,FusionF07A,if=RGB666 video=mxcfb1:dev=vdac,800x480M@60,if=RGB565 fbmem=16’

I’m also joining dmesg log if needed. link text

Touch on capacitive works fine and mouse on VGA display works too.
But the problem with it is that the VGA resolution always stay at 640x480 (default resolution I think).

Is ther a way to set it properly? at least at the same resolution as the Fusion07A.

Furthermore we would like to develop our own carrier board with HDMI and LCD connector. Could this work as I explained before with an iMX6DL or should we use a more powerfull board like iMX7 or iMX8?

Thanks you for advices.

Dear @Romain.Donze

On what plugin do you run your Application? Is it X11, EGLFS or Wayland?

The problem is that the Fusion07A and the VGA use the exact same interface. Therefore, the VGA output should also be 800x480 maybe your display just doesn’t know this resolution and thinks it is 640x480.
On this block diagram you see that VGA and parallel RGB share the same interface:

If you design your own carrier board you could use HDMI from iMX6DL. HDMI is available trough the small FFC connector on the back. We also sell an HDMI adapter for testing:

The iMX6DL is okay for what you do. The iMX7 is slower than the iMX6. The iMX8 could also be an option. However, the iMX6DL should fit if you don’t do a lot of 3D graphics.

One more thing. One problem the propriatery version of the iMX6DL graphics driver has is that it doesn’t support GPU accelerated graphics on both screens properly. Therefore, you may want to use the open source version. If you compile boot2qt yourself you would have to add the following line to your local.conf:

MACHINEOVERRIDES .= ":use-mainline-bsp"

Also see:


Ok I understand the fact that VGA and display connector share the same interface .

But I know that my vga display “support” 800x480 because if I set it so:

setenv vidargs ‘video=mxcfb0:dev=lcd,800x480M@60,if=RGB666 video=mxcfb1:off fbmem=8’

it seems to work on VGA but on my LCD it seems like the resolution isn’t as good as set with “Fusion07A”

maybe there is something to do with the timing?

Thank you for your answer on the HDMI too. I think I can go with the iMX6DL since our app doesn’t need as much graphics power except for dual screen capabilities.


Hi @Romain.Donze

Probably your display needs to put the resolution of 800x480 into its own native format (e.g. 1920x1080) and the image therefore looks ugly. However, if you properly use two separated interfaces (HDMI + parallel RGB), the image should look fine.