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DLP4500 Trigger Out

Other Parts Discussed in Thread: DLP4500, DLPC350

I am using the DLP4500 GUI in pattern sequence mode with a video source streamed from a PC over HDMI. Everything works correctly but I want to confirm the limits of triggering out in this mode. In my experience the trigger out isn't received upon changing the image sent to the DLP4500 over HDMI but upon the pattern exposure duration. I have a large amount of images to stream to the DMD and I would like the trigger out to correspond to the change in image at the DMD. Is this function only available using the flash memory?

  • Hello Dillon,

    Could you please further elaborate your requirement?  You are using the DLP4500 EVM with external pattern (trigger mode 0). The trigger out 1 signal will correspond to each pattern exposure. The Trigger out 2 will correspond to start of each pattern sequence. A sequence can consist of multiple patterns.

    Please refer to section 2.4.3.2 Trigger Controls (page 40) of DLPC350 Programmer guide.for details.

    http://www.ti.com/lit/ug/dlpu010g/dlpu010g.pdf

    regards,

    Vivek

  • Vivek,

    I am using the video port in pattern sequence mode. My observation is that trigger out 1 does not correspond to a change of the image that I display on the DMD as a second screen (e.g. If I keep the same image on the screen I still observe a trigger out). Instead the trigger out 1 is always observed at the value set for pattern exposure (e.g. if it is set to 16667 us I observe the trigger every 16667 us). I've exhausted the manuals and forum and I want to confirm that this is normal operation before I commit to a workaround. Is this a limitation of using the video port?

    Thank you,

    Dillon Kopecky

  • Hi Dillon,

    If I understand you correctly, you are streaming continuously over HDMI and you would like to be able to generate a trigger signal only when the scene content changes.  This is an interesting application and it sounds like a useful feature but it would require the DMD controller to be able to sense differences in the incoming video content.  I'm sure Vivek or someone else at TI can confirm the DMD controller used in the DLP4500 chipset is unable to do something like that.

    If you know that you will always be sending a specific number of frames of the same pattern before changing to the next pattern then you you could try using external logic to count trigger1 pulses and then generate your own customized trigger.  

    - Layne

  • Layne,

    You are correct. I thought so too and I just want to be sure I am not missing something. 

    Thanks,

    Dillon Kopecky

  • Hello Layne, Thank you. Appreciate it.

    Dillon,  Did you experiment with  Sequence Settings [Variable Exposure] mode? In this mode the exposure time is based on the per patterns (input). This may be able to meet your requirement. Please refer to" 3.3.2 Sequence Settings [Variable Exposure]" (page 32) of EVM user guide.

    http://www.ti.com/lit/ug/dlpu011f/dlpu011f.pdf

    Regards,

    Vivek

  • Vivek,

    I have tried Sequence Settings mode, however with video mode as the input the trigger still only occurs every time the exposure period time is complete. This is unrelated to what is displayed on the DMD. 

    Thanks,

    Dillon Kopecky 

  • Hi Dillon, 

    As per Layne Jenkins's reply, the DLPC350 or the DLP4500 DMD is unable to differentiate between any image content. So image content based trigger outs are not supported. 

    Thanks & Regards,

    Hirak.