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Light Commander input triggers?

Pete Thompson
Intellectual 465 points
Other Parts Discussed in Thread: DLPC200

Hello,

We are trying to figure out where the external input triggers are located on the circuit board.  We were told, "The external triggers can be provided through header J18, pin 2 (3.3V) and header J12, pin 1 (1.8V)."  However, so far we are unable to locate these jumpers on the actual circuit board.  As far as we can tell, the actual board and the schematic designs don't really match so we're a bit confused as to where we're supposed to look.

An alternative is to use the software trigger mention in the documentation, but so far we've been unable to locate an API that allows us to invoke the software trigger. 

Here's a bit of background on why I'm asking these questions:  We have cameras connected to the projector's Sync1 and Sync2 pins to trigger on each image being projected.  However, due to the lack of a "Run Once" ability, the projector will automatically loop through its preloaded images until we stop it, which can overwhelm the cameras and/or we end up with too many images.  So now we are trying to find workarounds to get the projector to cycle through its preloaded images only once.

This is where the input triggers come in; we're hoping that if we could connect a timing board to these pins, we could then control exactly how many images the projector will cycle through before it stops.  Unfortunately we haven't been able to locate these triggers so far. 

Does anyone have any advice or can point us to either the pin or how to use the software trigger?  And how fast is the software trigger?

Thanks!

 

  • 0
    TI__Prodigy 450 points

    Hi Pete,

     

     

    For connecting an input trigger try the following:

     

    There is a voltage translator between the DLPC200 and the EXP connector (expansion connector) on the LightCommander schematic. This voltage translator (U23) is initially set to be enabled. VCC_EXP must be in the 1.8V-3.3V range. If it isn't, the bi-directional voltage translator on the IO signals will not function properly (see note on sheet 20 of the schematic).

     

    Using the SYNC_IN0 (which is a 3.3V signal) for example, if you want to connect an input trigger without making any modification to the board try the following steps.

     

     

    1. Connect VCC_EXP (J505-Pin2) to 3.3V.
    2. Connect your input signal (a 3.3V level signal/trigger at some frequency) to the EXP_CON_SYNC_IN0 signal (J505-Pin6).
    3. Using the LOGIC GUI: Set the GUI for Structured Light and static memory. Set the frame rate to match your input signal, set the 3.3V Ext option for the Frame Trigger (Vsync) option.

        

    Best regards,

  • 0 in reply to tsolo
    Prodigy 50 points

    Hi,

     

    we connected an external trigger as you suggested, but it does not seem to work. We set the GUI to structured light mode with static memory and set the vsync option to 3.3V external trigger. If we then press play or step, the projector continuously displays all images (play) or one image (step) even if I do not send any trigger signal. You mention that we need to set the frame rate to match the input signal. However, our input trigger is actually irregular and I thought this would be ok as the projector would just switch to the next image whenever there is an input trigger. Or am I mistaken and the input trigger has to be regular, and the projector will basically lock onto the signal?

     

    Thanks

  • 0 in reply to tbo
    TI__Mastermind 45315 points

    Hello tbo,

    Welcome to the LightCommander section. 

    For your particular scenario please try to the following to see if it gives you the desired result:

    1. Under the "Workflow" tab go down to the "LED Illumination Time (Camera Exposure Time)" section. 
    2. Try setting the Time to [Max Time - 120 us].  Max time should be shown out to the right in this section and is calculated from the Frame Rate.

    This should cause the system to wait for the next sync (input trigger) whenever it comes.

     

    Fizix

  • 0 in reply to Fizix
    Prodigy 50 points

    Hi,

    Thanks for the suggestion, but so far no luck. I recompiled the system, programmed and the updated the flash memory of the light commander. Once I have done this, the light commander will display the structured light images at the framerate I set in the GUI. However, the sync is set to use the external 3.3V trigger, yet it displays images even if I don't send any sync.

    I am confused about the minimum framerate requirement. Why is there a minimum framerate? If I don't send a sync on the input trigger I will be below the minimum framerate. Might this be the problem?

    Cheers

    tbo

  • 0 in reply to tbo
    Prodigy 50 points

    Hi,

    You can find a photo of our trigger connections here:
    http://dl.dropbox.com/u/4739642/LightCommanderExternalTrigger.pdf

    As you can see, we attached the 3.3V to the Pin 2 of J505, and an input trigger cable with the same voltage to Pin 6. Did I miss anything? Perhaps this helps in resolving the problem.

    Cheers

    tbo 

  • 0 in reply to tbo
    TI__Mastermind 45315 points

    Hi tbo,

    First about your minimum framerate.  I believe that is meaningful when you are using the "auto trigger"   I do not think that is the issue.

    Your setup looks right (from the picture).  Would it be possilbe to get screencaptures of your "Workflow" tab entries?

    Regards,

    Fizix

     

     

  • 0 in reply to Fizix
    Prodigy 50 points

    Hi Fizix,

     

    thank you for helping me out on this!

    You can find the screenshots of my workflow here:

    http://dl.dropbox.com/u/4739642/lightCommanderSettings.pdf

     

    Cheers,

    tbo

  • 0 in reply to tbo
    Intellectual 465 points

    We are pretty much in the same boat -- we have wires hooked up to the same pins, and have the same workflow that tbo posted.

    It looks like the projector is still running on a loop internally, though, so the triggers still don't seem to run as expected. It's actually kind of hard to tell what the triggers are doing, but it looks like it might be the same issue when using the ManualStep function:  It can advance to the next frame, but as long as the projector is still looping on the same image, it's activating the output triggers on the same image, which is not what we want.

  • 0 in reply to Pete Thompson
    Prodigy 50 points

    Hi,

    we are finally a step further. The problem is that the compiler does not keep the setting to use the 3.3V external trigger. Have a look at the batchfile that is created. It keeps "setDataSource 3" instead of "setDataSource 4". Change this, and use "Run Batch File". It should work then. LogicPD know about it and I expect it to be fixed in the next software release.

    Nevertheless, I still have an issue with triggering. I trigger the projector with 24 fps and I can see that the illumination engine gets triggered. However, I do get sometimes some weird noise patterns or even no pattern at all is projected. I am in contact with LogicPD to fix this, but it would be great if anyone has a suggestion.

    Here you can find a video of the projected patterns which we record with a camera that is triggered by the same signal:
    http://dl.dropbox.com/u/4739642/LightCommander/triggeredShotsCamera.mov 
    frame 0 and frame 1 should be shown continuously, but as you can see frame 3-6, 16-18, 28-29, etc that a strange noise pattern is projected. frame 134 is completely black...
    I recorded the same projected images with a 24fps camera, which is otherwise unsynchronized. Nevertheless you can see exactly the same there as well:
    http://dl.dropbox.com/u/4739642/LightCommander/triggeredShotsVideo.mov 

    Cheers

  • 0 in reply to tbo
    TI__Mastermind 45315 points

    Peter and tbo,

    We were able to recreate the issue here with defaulting back to internal trigger instead of the 3.3 volt input trigger.  As tbo indicated, Logic-PD is aware and is testing a fix that should be in the next release. 

    Regarding the the "noise" pattern, we are working with Logic on this.

     

    Fizix

  • 0 in reply to Fizix
    Prodigy 40 points

    Hi all,

    How about the software trigger? No API for software trigger?

    Thanks,

    Son.

     

  • 0 in reply to Son Hua
    TI__Mastermind 45315 points

    Hello Sun,

    Please refer to the following document available on ti.com/mems under the LightCommander:

    http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=dlpa024a&fileType=pdf

    I hope this helps,

    Fizix

  • 0 in reply to Fizix
    Prodigy 50 points

    Hi everyone,

    I've been using your recommendations and managed to get my DLP to work through the trigger. Does anyone know what voltage range that it will accept? I've got an external trigger that fluctuates and I was hoping someone would know what range (eg 3.0V - 3.6V) the DLP can read.

     

  • 0 in reply to Fizix
    Prodigy 50 points

    Hi again,

    I was also wondering if there's a limit on the pulse length that the LightCommander can read. I have a source that's sending out a fairly short pulse. Would the LightCommander be able to read it? (its a 32 microsecond pulse)

  • 0 in reply to eric fritz
    TI__Mastermind 45315 points

    Hello Eric,

    Welcome to the DLP section of the TI-E2E Community.

    The voltage translator that was referenced earlier has a range from 1.8 to 3.3.  You may want to put a votage divider in on the signal to keep the voltage below 3.3 volts.  You need to make sure that the lower voltage goes below 1 V (ideally down to zero) and the the min peak voltage needs to be above 2.25 V.

    The Light Commander should easily be able to sense an input pulse width down to 1 msec.

     

    Fizix

  • 0 in reply to Fizix
    Prodigy 115 points

     

    Dear All,

    I would like ask about the Sync1. I connected it to an oscilloscope and the peak voltage of the square pulse that I got was 0.27V. I think it is not high enough to be detected by an external device. Would you suggest on that? 

    Regards,

    Fahri

  • 0 in reply to Fahri Yaras
    TI__Mastermind 30875 points

    Hi Fahri,

    If i understood correctrly, Sync1 do you mean the the middle BNC connector from the USER SYNCS  (3 BNC connectors) on the LightCommander? If so then you should get it around 3.3volts.  Is that what you are looking for?

    Let me know if you are looking for something else.

    Regards,

    Sanjeev

     

  • 0 in reply to Sanjeev
    Prodigy 115 points

    Hi Sanjeev,

    Yes you understood correctly. I connect the oscilloscope one of the BNC connectors and what I observed is Vpp = 0.27V. I think there is sth wrong with the oscilloscope. Thank you.

    Regards,

    Fahri

  • 0 in reply to Fizix
    Expert 1705 points

    Hello,

    Please let me ask about the software trigger.
    I am still wondering how to use the software trigger. What does trigger the VSYNC in this mode?

    If this software trigger is available, please give me some advice.

    Thank you and best regards,

    Rossinag

     

  • 0 in reply to Rossinag
    TI__Mastermind 30875 points

    Hello Rossinag,

    Software trigger mechanism works just like external hardware trigger. Basically software control VSYNC generation in the system. Can you please let me know how do you plan to use this option in the system? This is because right now there is no direct dedicated API available to expose this functionality in the system.

    Regards,

    Sanjeev

     

     

  • 0 in reply to Sanjeev
    Expert 1705 points

    Hello Sanjeev,

    Currently, I'm using the DLP_Display_DisplayPatternManualStep for the purpose of a kind of software trigger. And this is enough to me now.
    Thank you for your comment. I just wanted to know the diffrence between the real software trigger and my software trigger functionality.

    Thank you again,

    Rossinag

  • 0 in reply to Fizix
    Prodigy 50 points

    Hi Fizix

    I am trying to make an external trigger as well with DLP commander. So connections on the J505 are the following:

    3.3V or something below at pin 2 as VCC_EXP

    Trigger at pin 6 as EXP_CON_SYNC_IN0

    That is all I could find on DLP LightCommander Controller Board Specification. However the guys who realized the external trigger correctly showed in the picture some other connections on J503, is it correct? Could you give some more information about that? I did not find it documented anywere ...

    Thanks

    Riccardo

  • 0 in reply to Rossinag
    Prodigy 10 points

     

    Dear community,

    I am interested in using the software trigger to alternate two images uploaded but haven't been successful. Could you tell me how to do this?

    I set the Frametrigger option as a 'software trigger.'  Then in the matlab console, after loading the shared library, I sent the command, 'DLP_Display_DisplayPatternManualStep. But, the image was not turn to the next image. 

    Am I doing right? I will appreciate your comment.

     

    Sam

     

  • 0 in reply to Sam Bae
    TI__Mastermind 30875 points

    Hi Sam,

    Refer my earlier reply on 27 Aug 2011 5:45 AM in this thread.

    Short answer is, currently there is no API to make "Software trigger' work. So you will need to wait until we provide one.

    You should also understand that it is not suitable to use 'software trigger' for DLP_Display_DisplayPatternAutoStepForSinglePass () and DLP_Display_DisplayPatternAutoStepRepeatForMultiplePasses() APIs as you cannot achive the timing with "software trigger".

    You can use for DLP_Display_DisplayPatternManualStep () API.

    Regards,

    Sanjeev

  • 0 in reply to Riccardo Storchi
    TI__Mastermind 30875 points

    Dear Riccardo,

    J505 connector is correct for external hardware trigger.

    If I understood correctly you are not able to get the external hardware trigger working. From your explanation your connection on the J505 looks proper. Only thing i suspect could be related to Frame Trigger (VYSNC) configuration in the LightCommander(TM) Control Software.  After setting hit run button to load the solution/configuration.

    Make sure you are  setting this properly -

     Note - Trigger source must be properly selected; try selecting between Rising & Falling Edge.

    Regards,

    Sanjeev