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DLPC900: "DMD reset" in first pattern of sequence in pattern-on-the-fly mode

John Abrahamsen
Prodigy 40 points
Part Number: DLPC900
Other Parts Discussed in Thread: DLP9000,

We are using the DLPC900 for the DLP9000 master and slave in our projector.

Now we are noticing issues with a "double flash" when starting the sequencer. It is reproducible ever time the sequence is started. Symptoms:

* We use pattern-on-the-fly mode and upload a sequence of 2 images. Does not matter what bit depth is used.
* Sequencer is started
* Light output from our own LED driver is started with output trigger
* Image is shown a few usec.
* Light output from our lens seems to be gone, most probably the DMD mirrors is unexpectedly flipped to full off state.
* Light output restarts and correctly images the given amount of time as dictated by LUT definition.
* On the next pattern of the LUT definitions, this behaviour is not seen.
* Must use a high-speed camera to observe it fully as the fast blink is too fast to see with the naked eye.

As our own software and your example software "DLP LightCrafter 6500 & 9000" exhibits the same software. I stress that it is difficult to perceive with your eyes as the blink or DMD "reset" is too fast to see with your eyes. The triggering of our external LED driver is continuous throughout the whole sequence, this has been verified with an oscilloscope, meaning that light is indeed hitting the DMD, which leads me to believe there is some kind of a reset of the DMD during the first pattern being displayed. The two patterns produced is correct according to the uploaded patterns,  but we would like to have constant imaging with no intermediate reset.


Kind regards
John

  • 0
    TI__Intellectual 1080 points

    Hi John,

    Welcome to TI E2E forum :)

    While I try to reproduce this scenario and get back to you, Could you please tell me if you are able to reproduce the same with pre-stored pattern mode as well. This is because of the same base sequence getting used for both POTF and Pre-stored pattern mode. 

    Thanks

    Sachin

  • 0 in reply to Bhatta
    Prodigy 40 points

    I have not tried pre-stored pattern mode. I have attached a video I made of the behaviour seen for POTF. Using just one pattern and your software to upload it and start the sequence after a fresh cold boot. The settings used are the defaults one for your program. I must again stress that you need to use high-speed camera to see it.

    Version is 5.0.0.

  • 0 in reply to John Abrahamsen
    TI__Intellectual 1080 points

    Hi John,

    Thank you very much for sending the video. As far as I can see , it is very evident in the video , the occurrence of a flash. What do you mean by using a high speed camera?

    Thanks

    Sachin

  • 0 in reply to Bhatta
    Prodigy 40 points

    Hi Sachin.

    I mean that the video is captured with a high speed camera to slow down time. With a regular camera you will not see it, or it will be not very apparent at least.

  • 0 in reply to John Abrahamsen
    TI__Intellectual 1080 points

    Hi John,

    May I know whether you are controlling the DMD with TI provided EVM or you have built your own board. If you are using your own board, could ypu share the schematic of the board?

    Also, if you are not using TI software (I assume you are), could you point me the changes you have made? If you are using , then could you try loading the released version of software in your setup?

    I tried reproducing the issue and I probed the DMD reset signal. I cannot observe any discrepancy in the DMD reset signal with TI provided EVM. 

    Thanks

    Sachin

  • 0 in reply to Bhatta
    Prodigy 40 points

    Sachin, we have found the issue. It is not related to you. Thanks for your support.

  • 0 in reply to John Abrahamsen
    TI__Intellectual 1080 points

    Hi John, 

    Thanks for informing. If it is not related to the design of your product or not confidential , could you please post the issue and solution so that it might be helpful for others as this is a common forum.

    Regards

    Sachin