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High speed b/w patterns - Pico vs Lightcrafter

James Davis1
Prodigy 160 points
Other Parts Discussed in Thread: STRIKE

I bought a Pico 2.0, but have yet to get it to work. I'd be happy to buy the LightCrafter or other product, but since I didnt get the right thing previously, I thought I better ask about my application before buying the next part.

I want to run some perceptual tests on what humans see with various b/w patterns at high speeds. Ideal things I need:

  • Controllable speed. I'll settle for constant 1000Hz+ and the ability to simply double/triple/etc frames to get 500Hz/333Hz/250Hz/200Hz/166Hz, etc, but actually setting the frame rate would be great.
  • True b/w patterns would be preferable with RGB LEDs all simultaneously on, but I could settle for single LED monochrome. I dont prefer high speed RGB in sequence since thats complicating my perceptual experiment. 
  • Easy way to control the device. I prefer to run it from my Win7 laptop. I bought a Pico2.0, but have yet to get a BeagleBoard and whatever else is needed. A simple Win7 GUI that lets me set patterns and frame rate would make me happy. Ideally its 5 minutes from plugging things in to messing around with patterns, instead of a long process of install this and that.
  • Ability to turn off all gamma and other non-linear mappings. I want to be able to drive the display with inverted patterns which should sum to an even grey field when they are above the human flicker fusion threshold. For B/W this shouldnt be an issue, but if there is a greyscale mode, then I want the integrated light output of the two frames 0x00/0xFF to be the same as the 0xF0/0xF0. This isn't true when there is gamma processing happening between the input values and the actual light output.
My secondary need, which hopefully could be dealt with on the same device, but doesnt have to be: Display 180Hz video with a sync pin that I can control shutter glasses. I'm working on 3D TV applications but need to drive with a 3-subframe pattern instead of the normal 2-subframe pattern. Again I prefer driving from Win7, and need to turn off gamma to get linear light output. I can accept b/w or reduced bitdepth color.
I currently think the LightCrafter satisfies my needs, but I previously thought that about he Pico 2.0. If the LightCrafter does satisfy my needs, then I also need a list of whatever extra components I need such as cables etc to actually run the device.
  • 0
    TI__Genius 9935 points

    James,

    I just responded to your questions about the Pico Kit v2.

    You will find the DLP LightCrafter to much more user friendly, and much more capable as a platform.

    There are only three items that you will need to use the DLP LightCrafter:

    1) PC (Windows, linux, OSX) running the LightCrafter control GUI (download http://www.ti.com/lcrfirmsw11ver2 )

    2) USB to USB-mini cable (readily available)

    3) 5V 2A power supply. See http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=t1212-p12p-nd. Also, the PS supplied with the Pico Kit will work.

    The DLP LightCrafter should be a good match for your requirements. Please review the DLP LightCrafter User's Guide http://www.ti.com/lit/ug/dlpu006a/dlpu006a.pdf. Also, look at all of the information available from http://www.ti.com/tool/dlplightcrafter.

    Please let me know if you have further questions.

  • 0 in reply to Pascal DLP
    Prodigy 160 points

    Thank you for the confirmation that its straightforward to connect the LightCrafter to a Win7 machine.

    I'm a bit confused by the diamond pattern.  I'm under the impression that I'm going to drive this with a rectangular video signal. This means something is getting resampled, certainly in space, and possibly in time. Normally this is not an issue for office projectors, but anyone displaying fast patterns and/or structured light is going to want to know exactly what is coming out of the projector. In particular during the resampling, any DLP pixel will have to be either a nearest neighbor lookup from the input rectangular grid, or a bilinear resampling from 4 pixels. If its nearest neighbor, then the time pattern will be exactly as specified in the rectangular grid. However if its doing blinear resampling, and the neighbor pixels are say 0 [0000 0000] and 128 [1000 0000], then the interpolated pixel might have value 64 [0100 0000] (all assuming 8-bit). But if I'm trying to code specific time slices with light or no light, the 64 pattern is displaying light in a slice that I think is supposed to be black. 

    So, is the interpolation from rectangular to diamond all nearest neighbor lookup, so that there is a mapping from DLP pixels to rectangular pixels, but there is no intensity or time pattern interpolation going on? (Nearest neighbor pixel mapping would be completely the *wrong* thing to do for a normal office projector, but for structured light I'd rather have understandable jaggies than blurry edges that produce unexpected light output.)

    Along these same lines, if I want actual straight lines output I'll have to input diagonal lines in the video source - correct?

    Although I've read the Pico docs in detail, I have only glanced through the LightCrafter docs, so feel free to tell me to RTFM if this is addressed. =)

  • 0 in reply to James Davis1
    TI__Genius 9935 points

    James,

    The DLP LightCrafter has several modes: One of these is the HDMI video input mode, which accepts several input resolutions, but scales them all to 864x480 mapped to the 608x684 diamond array DMD. There is an external pattern mode (not currently supported by the LCr GUI), which receives the data over the HDMI as 24 bit RGB, but can display the data as 24 1-bit bitplanes, or other bit-depth combinations. The video and the LCr should be set to 608x684 resolution, and the pixels will be one-to-one mapped to the DMD.

    There is no video picture processing, except for Gamma, which can be turned off (probably will require the API - will check).

    The triggers for synchronizing with a camera can also be used. However, in the case of external HDMI patterns, it only makes sense to use the LCr to trigger a camera.

    With respect to the diamond matrix and diagonal lines, the production of diagonals should be handled in the generation of your external (or internal uploaded) patterns. The mapping of arbitrary diagonals to the diamond matrix is your choice. If you are in 608x684 resolution, the LCr will not remap the pixels.

    I do refer you to the complete LightCrafter documentation, which is available from http://www.ti.com/tool/dlplightcrafter.

    I hope this helps.

    >>> I modified the original posting by adding the strike out above. The external pattern mode is supported by the GUI, but not labeled as such - and with a couple of "workarounds" to set up the trigger for a camera. I also modified the statement about turning off the gamma. I will need to check whether this needs to be done in 1 bit mode (I don't think so) and how it can be done. See my additional posting below.   Pascal 03/06/2013 <<<

  • 0 in reply to Pascal DLP
    Prodigy 20 points

    Hi Pascal,

    I have  couple of questions relating to your response. 

    Pascal DLP said:

    The DLP LightCrafter has several modes: One of these is the HDMI video input mode, which accepts several input resolutions, but scales them all to 864x480 mapped to the 608x684 diamond array DMD. There is an external pattern mode (not currently supported by the LCr GUI), which receives the data over the HDMI as 24 bit RGB, but can display the data as 24 1-bit bitplanes, or other bit-depth combinations. The video and the LCr should be set to 608x684 resolution, and the pixels will be one-to-one mapped to the DMD.

    I am looking to have the DMD display the data as 24 1-bity planes. But, if the LCr GUI doesnt support it, I am curious what are my alternatives in setting the LCr to display data as 24 1 bit planes. Could you point me to the information ?

    I am guessing I have to control it over USB. Would be very helpful if you could link me to any code snippet or demo code that will get me started on this. Thanks!

    FYI, I am using the DMD in my imaging pipeline and really want it to display the binary patterns one-to-one on the DMD.

    thanks

    -as

  • 0 in reply to Aswin Sankaranarayanan
    TI__Genius 9935 points

    Aswin,

    Welcome to the DLP & MEMS E2E forum.

    I will assume that you are using the DLP LightCrafter GUI v3.8 (the one currently available from http://www.ti.com/tool/dlplightcrafter - DLP LightCrafter Firmware and Software Package v1.1 11/08/2012).

    If you select and set the "Display Mode" as "HDMI Video", then select the tab "HDMI Video" you will see "Video Mode Setting" where the "Bit Depth" and "Frame Rate" can be selected. For external 1 bit structured light via the HDMI input, set a "Video Setting" "Resolution" of 608x684 (1-1 pixel mapping) and a "Bit Depth" of 1 bit. For a "Frame Rate" of 60 Hz, each bit of the 24 bit RGB input will be displayed in sequence as an un-weighted bit plane for a resulting 1440 1 bit patterns per second.

    A work-around is required to set the LCr trigger output for operation with the HDMI video mode. The GUI doesn't present the trigger controls in the "HDMI Video" tab. So, you must first select the "Display Mode" = "Pattern Sequence" then select the tab "Pattern Sequence". There you can enable the "Output Trigger Setting" and set the "Delay" and "Pulse Width (us)" of the trigger output signal which can be used to trigger a camera for each displayed frame. Once this is setup, you can then reselect the "Display Mode" "HDMI Video" and do the settings above.

    We have not thoroughly tested these instructions. We are planning to make this more straightforward in a future release of the GUI.

  • 0 in reply to Pascal DLP
    Prodigy 20 points

    Pascal,

    Thanks for the fast reply.

    This is perfect. I think it should be quite OK even if the trigger doesnt work.

    Would have any suggestions for windows or mac software for pushing out 60 fps video. I have a decently powerful video card on my desktop that runs windows 7.

    -as

  • 0 in reply to Pascal DLP
    Prodigy 160 points

    Thanks. If there is a 1-to-1 mapping of pixels then my concerns about the resampling will not likely apply. Similarly if there is a 1-bit mode then I dont think gamma is a concern (since neither black nor white gets adjusted by the application of a typical gamma curve). I can get the details of the various mappings from the docs. Much appreciate the confirmations that the LightCrafter will suit my needs. I'll go check on ordering one.

  • 0 in reply to Aswin Sankaranarayanan
    TI__Genius 9935 points

    Aswin,

    Suggestion for software to push out 60 fps video (from many types of media): VLC Media Player (Windows, Mac OSX, Linux)

    See: http://www.videolan.org

  • 0 in reply to Pascal DLP
    Prodigy 160 points

    Link to known working power supply?

    This page at TI points to an obsolete digikey part.

    http://www.ti.com/tool/dlplightcrafter

    http://www.digikey.com/product-detail/en/EMSA050300-Z12P/T1228-Z12P-ND/2921387?cur=USD

    Your link earlier in this thread also does not seem to point to a specific part. I understand 5V 2A well enough, but I'd like to get the right connector and polarity. Also projectors are sometimes finicky about high frequency noise in the power, and I've had issues getting random power bricks for other projectors and cameras, so if you happen to recommend a part, I'll just get that one.

    Thanks

  • 0 in reply to James Davis1
    TI__Genius 9935 points

    James,

    Sorry. You are correct. The link you copied has gone stale. We will get it fixed.

    Here is the link to the correct power supply for the DLP LightCrafter: http://www.digikey.com/scripts/dksearch/dksus.dll?vendor=0&keywords=t1212-p12p-nd

    The connector is an odd one, not seen much outside Japan. It is a quite thin coaxial connector. The available space on the LightCrafter was what led to the choice of that particular connector.