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L515 external hardware sync information

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T Loomans

I'm looking for some more information on the external hardware sync of the L515. I've tried to sync the camera with a conveyor belt with rotary encoder, but I can't figure out when exactly an image is taken after the external trigger signal is set. Could you maybe help me with the following questions:

  • What is the maximum voltage that may be applied to the external hardware sync port? (can it handle 5V?)
  • Does the external hardware sync port need some type of pull-up/pull-down resistor or some other type of termination to give it a clean signal?
  • When exactly after the trigger signal is set will the image be taken? The whitepaper says that there is a 60ms setup time. Does this mean that after exactly 60.000ms always a frame is taken? Or can this differ between triggering, and if so, how much does it vary. 
  • How long does it take to make the image, is this exactly 33.000ms or is this shorter?

Thank you in advance.

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2 comments

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  • Zulkifli Halim
    • Edited

    Hello T Loomans,

    Thank you for contacting us.

    1. 3.3V is the only validated voltage value for the sync signal. Do not use any voltage other than 3.3V.
    2. Section 1. Connecting the cameras of the L515 Multi-Camera paper shows that no extra resistors are necessary.
    3. Section E. External Trigger shows the timing diagram. Frame capture begins immediately after the 60 ms setup time and this cannot be changed.
    4. A full 33 ms is required to capture a frame. This corresponds to the fixed 30 fps framerate -- 1 second/30 fps = 33 ms. The frame rate is fixed at 30 fps so the 33 ms cannot be changed.

    Regards,

    Zulkifli

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  • T Loomans
    • Edited

    Dear Zulkifli,

    Thank you for the response. After some experimentation and another support question I've found out that your answer is actually incorrect. According to the answer from Jesus, the setup time is not exactly 60.000ms but it can differ between triggering.

     

    So setup time is about 2 frames (60ms ~= 2*33ms) before a good frame is available.

    It will depend on where in the cycle the sync signal is high. You may go high with the sync signal when a frame is already in the middle of its presentation.

     

    Also the frame capture doesn't start immediately after 60ms, the camera is always capturing and frame transfer only happens when the external trigger is high for a complete capture cycle after the setup time.

     

    With kind regards.

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