gray scale problem in video mode?

gy yoon

I'm trying to use the light commander as a second monitor. With a static gray scale image, the image is displayed just fine, but in video mode with DVI-HDMI connection, black looks green while white looks ok. I played with the setting for the duty cycles, but it didn't help much....Am I missing something?

Thank you for your advice in advance.

over 12 years ago

0 Sanjeev over 12 years ago

TI__Mastermind 30875 points

Hello Yoon,

Welcome to DLP&MEMS forum.

Did you try adjusting the Degamma setting ? Also check with another monitor if the source is sending proper video data.

Regards,

Sanjeev

0 gy yoon over 12 years ago in reply to Sanjeev

Prodigy 80 points

Yes, I did. I could make the problem better or worse by adjusting the degamma setting, but it is still there. The video source is fine on a typical LCD. I also checked the pin connection to the DMD, but it looked fine too.

thanks,

Yoon

0 Sanjeev over 12 years ago in reply to gy yoon

TI__Mastermind 30875 points

Hi Yoon,

Let me make sure you also tried Duty Cycle adjustment. Please confirm.

With respect to Color on Video Port the platform has only three control parameters namely Degamma, Duty Cycle and LED Strength.

Can you post the picture? We have tried displaying Grey Ramps here and we get proper image.

Regards,

Sanjeev

0 gy yoon over 12 years ago in reply to Sanjeev

Prodigy 80 points

yes, I've tried Duty Cycle too, but didn't solve the problem. I attached two images of a vertical gray ramp pattern, each from an LCD (upper) and the light commander (lower).

0 Sanjeev over 12 years ago in reply to gy yoon

TI__Mastermind 30875 points

Hi Yoon,

This clearly looks like a optical mis-alignment problem. You might need to open the Kit and see all the elements are in correct position.

I have included a picture showing the light path.

Another option you might need to try to confirm if it is optical problem.

Using Control software setup Kit to display 'Test Patterns' i.e., In the GUI under Workflow tab select Mode = Video, Data Source = Test Pattern Generator and then inside Test Pattern Generator select Solid Pattern with different colors, Verify each color is displayed properly. If NOT then definitely it is optical mis-alignment problem.

Regards,

Sanjeev

0 gy yoon over 12 years ago in reply to Sanjeev

Prodigy 80 points

Hi,

I've tried Test Patterns and all colors were perfect. This made me think that this problem might be something to do with HDMI video signal processing or connection...

Yoon

0 Sanjeev over 12 years ago in reply to gy yoon

TI__Mastermind 30875 points

Hi Yoon,

Yes, it is something to do with HDMI signal. Can you also try displaying full on Red, Green and Blue images via HDMI port. Anything not displaying properly confirms the issue.

Regards,

Sanjeev

0 gy yoon over 12 years ago in reply to Sanjeev

Prodigy 80 points

All colors are dominated/biased by green color as shown in the inserted image below. From left, they're supposed to be red, green and blue.

0 gy yoon over 12 years ago in reply to Sanjeev

Prodigy 80 points

Hi Sanjeev,

I just found previous discussions about exactly the same problem. Unfortunately, the discussion discontinued without solution confirmed.... I wonder if there has been any further invetigation on this?

http://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/f/387/p/121229/604789.aspx#604789

0 Sanjeev over 12 years ago in reply to gy yoon

TI__Mastermind 30875 points

Hi Yoon,

Normally the user updates whether the solution worked and some times they forget to update the thread.

Coming back to your problem. It is clear that the problem is in HDMI Video Data path. From the source side check if there RGB channels "offset" value is in range i.e., check Red and Blue low while Green is HIGH.

The next thing i recommend would be to try with another HDMI Cable. Then next step would be to verify if there is poor contct between the HDMI socket with the controller board.

Regards,

Sanjeev

0 gy yoon over 12 years ago in reply to Sanjeev

Prodigy 80 points

Hi Sanjeev,

Where can I find "RGB channels "offset" value"?

I've already tried at least 5 different HDMI cables, but didn't solve the problem.

How can I check "if there is poor contct between the HDMI socket with the controller board"? If it turns out to be a bad connection between them, how do I fix it?

thanks,

Yoon

0 Pascal DLP over 12 years ago in reply to gy yoon

TI__Genius 9935 points

Yoon,

Have you tried connecting your HDMI video source to another monitor via the HDMI connection? This would be to check if the source is providing the expected output.

0 gy yoon over 12 years ago in reply to Pascal DLP

Prodigy 80 points

Yes, I verified the HDMI using a typical LCD monitor.

thanks,

Yoon

0 Sanjeev over 12 years ago in reply to gy yoon

TI__Mastermind 30875 points

Hi Yoon,

I believe you are using PC/Dekstop/Laptop as source. In this case my suggestion was to goto the graphics card properties and check if the Brightness, Contrast, Offset settings showing reasonable values after connecting to the LightCommander hardware.

About the board debugging you may want to take the board to the soldering shop to verify for the HDMI connector issue. You can download schematics from the LOGIC website. You can access the documents from here http://www.logicpd.com/products/application-platforms/dlp-lightcommander-development-kit/#documentation

Regards,

Sanjeev

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gray scale problem in video mode?