LVDS output on Apalis i.MX6 (IXORA Board)

Technical Support
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1

I have been using my new Ixora board with Apalis iMX6 Quad 2GB with success and I tried connecting my LCD panel to Ixora using the LVDS pins available on the board.

I followed the guide at http://developer.toradex.com/knowledge-base/display-output-resolution-and-timings-linux

But I get no output from the LVDS, no matter what Framebuffer I set for LVDS.

I have used the following boot variable but to no avail:

setenv vidargs 'mxc_hdmi.only_cea=1 video=mxcfb0:dev=hdmi,1920x1080M@60,if=RGB24 video=mxcfb1:dev=ldb,800x600M@60,if=RGB666 ldb=sin0 fbmem=32M'

I also tried changing the first framebuffer to LVDS but again nothing is displayed on the screen:

setenv vidargs video=mxcfb0:dev=ldb,800x600M@60,if=RGB666 ldb=sin0

Am I missing something here?

Is there anything I have to set to get the output on the LCD?

I appreciate your responses.

Morteza

2

What version of the kernel are you using?

3

I am using Linux version 4.1.44-2.7.4

4

Hi

Note that when booting the kernel output will only be on mxcfb0 and the Vivante X11 driver only supports one framebuffer, also mxcfb0. So mxcfb[1-3] by default output a black screen.

Thus I would first try to bring up only the LVDS screen on mxcfb0.

setenv vidargs 'video=mxcfb0:dev=ldb,800x600M@60,if=RGB666 video=mxcfb1:off video=mxcfb2:off video=mxcfb3:off fbmem=32M'

Note that channel and colour mapping configuration needs to be done in the device-tree. I.e. the kernel parameter spl is not supported.

However the default is 18bit colour depth on the first channel.

With this set, what does the kernel tell about framebuffers? dmesg | grep fb.
Do you get signals on Ixora, X19 connector with an oscilloscope?
Do you have an issue with backlight, e.g. is the backlight switched on?

Max

5

Thanks Max.tx
It worked like a charm!

Is there a straightforward way to control BKL1_ON pin on LVDS connector? (Turning LCD on and OFF)
Based on the Ixora datasheet it is MXM3 Pin Number 286.

Sorry if it sounds trivial :slight_smile:

I am new to i.MX world, I come from TI Davinci background.
We normally set everything related to LCD in the user space there.

Thanks for your support

Morteza

6

Hi Morteza

You can control the backlight driver through the /sys sysfs.

Have a look here.

Max