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>200 Hz monochrome using HDMI input, FPGA processing of TTL pulse to modulate LED power

Jonathan Leong
Intellectual 265 points
Other Parts Discussed in Thread: DLPC300

Hi,

I'm hoping the Lightcrafter users and developers here could help me to determine whether Lightcrafter would be appropriate for the following application.

I'm programming OpenGL graphics, which I'd like to present using DLP Lightcrafter via the HDMI input. The graphics are monochrome blue, and I need to use high frame rates, >200 Hz. Bit depth should be 4 or 6 bits. Could anyone confirm that DLP Lightcrafter would support this use? Also, what requirements would there be for my graphics card? It's not clear to me whether Lightcrafter's high frame rates are specific to the onboard bit planes, or to any signal inputs, e.g. HDMI.

My graphics presentation also needs to be integrated with an imaging data acquisition system, and graphics presentation and imaging must alternate so that the imaging system never "sees" light from the Lightcrafter. Imaging frames are acquired at 700-1000 Hz, with maybe 50-60% duty cycle. The imaging system outputs a TTL trigger pulse every cycle, and I would like to use this signal, with a delay of a few hundred microseconds, to trigger graphics presentation for a few hundred microseconds. Has anything like this been done before?

I've implemented similar synchronization before using the TTL pulse and a delay to modulate the power driving the LED backlight of an LCD display - and I'm wondering if a similar "hack" would be possible with Lightcrafter - could I modulate power to the LEDs? Alternatively, this implementation requires additional electronics (for the delay and pulse generation). It seems like an FPGA could be well suited to do my signal processing. Would Lightcrafter's onboard FPGA be able to take the TTL pulse, and after a few hundred microsecond delay modulate power to the LEDs?

Thanks for your thoughts!

Jonathan

  • 0
    TI__Genius 9935 points

    Jonathan,

    Welcome to the DLP & MEMS E2E forum.

    There is complete documentation for the DLP LightCrafter available from our website http://ti.com/mems. Look especially at the DLP® LightCrafter™ Evaluation Module (EVM)

    User's Guide  http://www.ti.com/lit/ug/dlpu006a/dlpu006a.pdf.

    It sounds like you would want to use the external pattern mode. You will see that it is possible to do 4 or 5 bit depth monochrome at 240 fps, and 7 bit depth monochrome at 180 fps. The input is 60 Hz video over the HDMI, and the individual bit planes are constructed from the 24-bit RGB signal in each video frame.

    The LightCrafter also supports triggering in and out to synchronize to the displayed frames. Trigger delays can be set.

    It appears that the DLP LightCrafter will support your requirements, but you should review the documents to get a clear view of the LCr capabilities vs your requirements.

  • 0 in reply to Pascal DLP
    Intellectual 265 points

    Pascal,

    Thanks for your helpful response! Having looked through the User's Guide etc. I have a few follow-up questions:

    The User's Guide shows pattern rate as a multiple of frame rate, with 60 Hz frame rate listed as maximal. Is there support for higher graphics card frame rates, e.g. 85 Hz or 120 Hz, for faster pattern rates? Also, it seems the FPGA could enable even higher frame rates while still meeting my bit depth and color requirements. Do you have FPGA experience/resources that you could share? From the website:

    Programs an Altera Cyclone IV EP4CE6 FPGA that can be used in conjunction with the DLPC300 controller to enable even higher speed monochrome pattern display on the DLP3000 compared with using the DLPC300 alone. The optional FPGA allows users to multiplex two data input sources and provides a fully configurable I/O trigger for synchronizing cameras, sensors, and other peripheral devices. It also provides for additional LED control capabilities.

    I'm still uncertain about how best to take advantage of triggering, or if I need (or would be able) to work with the FPGA/DM365 at a more basic level. My sync trigger will come in at 700-1000 Hz, but not necessarily always the same or even very constant frequency, while the stimulus will need to be a fixed 240 fps. Because the sync trigger frequency isn't easily related to the frame rate, how can I process the sync trigger and do bit plane presentation asynchronously? My hope was to run the DMD at 240 fps, and power the LED light onto it at only the "appropriate" moments signalled by the trigger. Again, any resources on custom FPGA/DM365 programming could be helpful!

    One last thing: in another thread (http://e2e.ti.com/support/dlp__mems_micro-electro-mechanical_systems/f/94/t/249542.aspx) you mention that there is a 1-to-1 mapping between the rectangular input signal and the diamond mirror grid of the DMD, but I didn't understand from your previous post what that mapping is. Also, is the diamond pattern typical of DMDs, i.e. commercial office projectors?

    Thanks again,

    Jonathan