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DLP6500FYE: Display Error In Video Pattern Mode

Ding Luo
Prodigy 135 points
Part Number: DLP6500FYE
Other Parts Discussed in Thread: DLPC900, DLP9000,

Dear all,

I am using EVM 6500 in the video pattern mode in GUI and have noticed something weird. When I specify just one single bit pattern with frame change unchecked, for example G0, I expect to see alternating on and off when gradually changing the G value of my pattern, i.e. off when G=0, on when G=1, off when G=2, and so on. However, the display does not follow this pattern and what's more weird is that several intermediate "gray" patterns will be displayed for some G value. As I understand, this should never happen for a single bit pattern.

I am pretty sure this must be a problem with this board since we have another board which works correctly as expected. All other modes are working correctly for this problematic board. Has any one seen similar problem? Does this have to do with software/firmware or hardware? And is there a way to fix it?

Best,
Ding

  • 0
    TI__Mastermind 43185 points
    Hello Ding,

    I need some clarification, because I am not understanding something. You indicate that you are using 1 bit patterns that are connected to different bit values of the video pattern? but are not connected to frame change.

    Could you provide a screenshot of the Video Pattern Mode setup page.

    Also it sound like if you connect another DLPLCR65000EVM using exactly the same setup (i.e. saved and reloaded), that it behaves as expected. Is this correct?

    Fizix
  • 0 in reply to Fizix
    Prodigy 135 points

    Hello Fizix,

    Thank you very much for your reply!

    I do not have the setup at my hand at the moment so I will try to add the screenshot later. In the GUI, I just specify a single pattern in video pattern mode, with one bit depth starting from G0. Frame change for this pattern is unchecked and repeat is chosen. Since it is a repeating one bit pattern, I think the exposure time is not very important, but anyways it's set to 1000µs. Then I just treat the DMD as my second monitor and try to change the color of a pattern in some drawing software. When I change the G value of the pattern, I expect to see the following change: G=0 DMD off, G=1 DMD on, G=2 DMD off, G=3 DMD on, and so on. But in practice the DMD variates with a different period and some intermediate gray is displayed instead of full on or full off. I also tried a single repeating pattern with one bitdepth starting from other bit positions, and they all have problems. For example, when I take a single pattern starting from G7 with one bit depth. Normally, DMD should be off for G=0 to G=127, and on for G=128 to G=255. But actually it is off for G=0 to G around 136, half on and off (weird gray state) for G around 137, and full on until G=255. I am monitoring the DMD using a high speed camera with appropriate exposure, but even with bare eye it is possible to see the "gray" state. And as I mentioned before, this EVM is working properly in all other modes, so I hope it is not a problem with the hardware.

    And you are correct that our other DLP6500EVM with exactly the same setup is performing correctly without any problems.

    Best,

    Ding

  • 0 in reply to Ding Luo
    TI__Mastermind 43185 points
    Ding,

    Thank you for the explanation, it is much clearer now. No need to send the setup screen on this.

    Please do me the favor of recording all the version information. Also, on the one that is acting up have you ever updated the flash with pattern data? And on the one that is not?

    I will need to talk to a couple of our engineers here to see if they can shed some light on this (if you will pardon the pun).

    Fizix
  • 0 in reply to Fizix
    Prodigy 135 points

    Hi Fizix,

    I have finally managed to locate the problem and luckily it's not the problem of the DMD. I am driving the DMD through HDMI connected to a Nvidea GTX 1050 graphic card. It turns out that the Output Dynamic Range is set to "limited" in the Geforce Control Panel, which leads to the problem in the Video Pattern mode. According to a thread on Reddit, after every driver update, the color range is set to "limited".

    Although I still don't understand the reason for the "gray" pixel when displaying a single one bit depth pattern, I am guessing that in this limited dynamic range mode, the graphical card is sending a weird data format which somehow disturbed the DMD's ability to display correctly.

    One thing worth mentioning is that while trying to locate the problem, I also tried to connect the DMD to the HDMI port of the motherboard, i.e. through Intel graphics. The video pattern mode also has problem but in a slightly different way than the nvidea graphic card. I've read that Intel graphics also have similar energy saving features, which I suspect are the cause of the problem. I didn't bother to find the solution for the intel graphics since I will be using output from the gtx card.

    When the Output Dynamic Range is set to "full", everything works perfectly. I think it's not a bad idea to mention this requirement in the manual of EVM 6500.

    Thank you again for your kind support!

    Best,

    Ding

  • 0 in reply to Ding Luo
    TI__Mastermind 43185 points

    Ding,

    THANK YOU for reporting back the solution you found‼ It is very unlikely we would have uncovered this issue. Thank you for your persistence, I think it may be very helpful to others.

    We will be updating some of the DLPC900/DLP6500FYE/DLP9000 documentation sometime in the not to distant future, but I don't have any dates.

    Thanks again!

    Fizix