Linux framebuffer problem

[madhu]

Hi

I'm getting following error while running the example project which is configured with linux frame buffer.

GDISP Framebuffer: Error opening the framebuffer device

[Joel Bodenmann]

The two most likely issues that cause this error are:

• Your Linux kernel has not been compiled with framebuffer support or it isn't enabled
• Your Linux framebuffer is in a non-standard location. Have a look at /boards/base/Linux-Framebuffer/board_framebuffer.h. The board file looks for /dev/fb0 and /dev/fb/0 by default.

[madhu]

Hi,

I solved "GDISP Framebuffer: Error opening the framebuffer device " and I'm successfully running ugfx with framebuffer in my host pc.

But when I'm  running it in my target machine(armv71 with linux kernel 3.0.35) I'm  getting one more error "Gdisp framebuffer: dispaly is 24 not 32 bits per pixel ".

How to enable 24 bits pixel format?

 

 

[Joel Bodenmann]

1 hour ago, madhu said:

I solved "GDISP Framebuffer: Error opening the framebuffer device " and I'm successfully running ugfx with framebuffer in my host pc.

Can you let us know what you had to do in order to resolve the problem?

1 hour ago, madhu said:

But when I'm  running it in my target machine(armv71 with linux kernel 3.0.35) I'm  getting one more error "Gdisp framebuffer: dispaly is 24 not 32 bits per pixel "

This means that the frame buffer provided by your Linux host is using a 24-Bit pixel format while your µGFX one is configured to a 24-Bit pixel format.
You can overwrite the default pixel format by setting GDISP_LLD_PIXELFORMAT in your configuration file. You should be able to figure out which format your Linux host uses first.

[madhu]

Hi,

Initially I ran my demo in normal user so it didn't work. So later I have done some research regarding frame buffer  then I come to know that I should run my demo with root user.

So I tried with root user and it started working...

[Joel Bodenmann]

Glad to hear that you got it working!

We added a note about this to the readme of the Linux-Framebuffer board file: https://bitbucket.org/Tectu/ugfx/commits/a972649d65b545031de1e88023acb39b1d7a26e3

[madhu]

Hi,

I'm able to run my project in both host and target machines.But I'm facing flickering problem in target machine(armv7).

I configured my host with  GDISP_PIXELFORMAT_RGB888. Here my demo is running very smoothly.  And I configured my target with GDISP_PIXELFORMAT_RGB565 . I'm able to run the demo in my target screen but screen is blinking continuously and also half screen I'm getting black and half I'm getting white.

Please help me if some had face this problem earlier..

[inmarket]

Note the pixel format specified for uGFX must exactly match the pixel format for the framebuffer in the Linux machine.

The pixel format in uGFX is setup at compile time not runtime so it cannot handle when the Linux framebuffer is not in the format it expects.

The problem you are describing on your target sounds very much like a pixel format mismatch problem.

[madhu]

Hi,

Still I'm facing flickering error with my frame buffer demo. My display is 24 bpp with 320x240 resolution.

I'm successfully running normal frame buffer application which is attached in the attachment. I'm suspecting there is a problem with pixel format.

I'm setting GDISP_PIXELFORMAT_RGB565 at board file if it is not correct please let me know what is the correct value or I need to change any thing else?

demo.c

[inmarket]

The pixel format must exactly match what your hardware expects.

So if your display 320x240 at 24bits then you will need to use something like GDISP_PIXELFORMAT_RGB888.

[madhu]

Hi,

If I use GDISP_PIXELFORMAT_RGB888 I'm getting following error.

GDISP Framebuffer: The display is 24 not 32 bits per pixel.

 

[Joel Bodenmann]

Please use the latest master of the official µGFX library repository. We fixed exactly that issue about two weeks ago:

I strongly recommend you to hit the "Follow" button on the µGFX Development blog to stay up-to-date about ongoing changes and fixes:

 

[madhu]

Hi,

Thanks for the support...

Yes its working now....

 

[Joel Bodenmann]

Happy to hear that!