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DLP6500FYE: 6500EVM video pattern mode background level

Part Number: DLP6500FYE

Hi there, 

I'm trying to obtain a setting to use Video pattern mode with a proper grayscale, but whatever I set, the background (code = 0 LSB) always has some reflected light. 

  This is the video pattern mode setting

  This is the projection image with Video mode 

  This is the projection image with Video Pattern mode

I'm using a Raspberry Pi (1920 x 1080, 60Hz, HDMI connection). How can I obtain a completely dark background using Video pattern mode? 

Thank you in advnace. 

Best, 

Yun

  • Yun,

    I am not familiar enough with the video output on the RasPi.

    Please check this link about CEA vs DMT modes for HDMI on the RasPi:

    https://www.raspberrypi.com/documentation/computers/configuration.html#hdmi-groups-and-mode 

    Fizix

  • Hi Fizix, 

    Thank you for your answer. 

    Then can you check the above parameters and let me know if they look okay? 

    This is what I got from raspberry pi using tvservice -s. 

    state 0xa [HDMI DMT (82) RGB full 16:9], 1920x1080 @ 60.00Hz, progressive

  • If possible, please advise me what should be done to obtain a full grayscale (0-255) using video pattern mode in terms of video input, frame rate, parameter settings. I don't mind slow frame rate since I'll project each image more than 1 sec. 

  • Yun,

    Could you please provide an image of the entire GUI screen while Video Pattern Mode is running?

    The parameters read from the RasPi seem to indicate that it is running RGB full.

    Are you using the LED_Enable signal to modulate your illumination?

    Fizix

  • Hi Fizix, 

    Yes, I think the video signal from RasPi seems okay. 

    When I connect LED_EN signal to the LED driver, it works okay and I can obtain almost dark background. 

    I have a few questions regarding this board. 

    #1: I wanted to have the same effect without LED_EN in the Video pattern mode. Isn't it possible without LED modulation? 

    #2: My other question is if there is any difference between Video mode vs. Video pattern mode in terms of linearity? 

    Video pattern mode seems to give more linear response, but sometimes it starts with minor flickering, so I need to software reset the board. 

    Thank you. 

    Best regards, 

    Yun

  • Hello again Yun,

    The exposure time you have does not fill the entire frame.  Try to increase the time up to about 16,666 us, or until it just causes the sequence abort flag to be triggered, then lower it by a few us and see if that improves the dark level without using LED_EN.  The difficulty is that at 60 Hz input the shortest bit(s) are shorter than the load and reset time of the DMD and the system uses LED_EN to turn of the light.

    Alternatively, you could see if it is possible to force 30 Hz rather than 60 Hz from the RasPi and see if the EVM will accept the input.  This will make the LSB display time longer than the load and reset time if using one 8-bit pattern from the input per frame.

    Fizix

  • Hi Fizix, 

    Thank you for your answer. I tried 30Hz, but for some reason, it does not work properly. Actually LED output is more flickering than 60Hz. So I had to go back to 60Hz and tried different exposure times. 

    I wanted to know if there is a way to get smooth grayscale without LED_EN pins, but it seems not possible. 

    However, I have learned new aspects of this board and will keep testing further. 

    Thanks!

  • Hello Yun,

    Thank you for letting us know. 

    Fizix