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SCH23
Associate
December 17, 2023
Solved

VL53L4CX spad map

Is there any way to get an overview of the 16x16 (time-integrated) SPAD array signals? I would like to see how the VCSEL spot looks on the SPAD matrix. Clearly, this information must be present on the chip itself, as it knows about its optical center. However, is it also possible to access this data via I2C somehow?

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John E KVAM
John E KVAMBest answer
ST Employee
December 18, 2023

Anne is correct in that it's not possible. But it leaves you wondering why. Turns out the photon data is coming in at something like 20 million photons per second. And we need to aggregate all that information, make a decision and get that decision back to the MCU in pretty short order. So we lose the data you want at the hardware level.

The sensor can decide which SPADs are on - but that happens before the collect. The Dynamic SPAD Selection is based on how many photons were received last collect. 

And we know about the optical sensor due to some really careful factory calibration. It's not real-time data.

 

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3 replies

Anne BIGOT
Anne BIGOT
ST Technical Moderator
December 18, 2023

Hello
It is unfortunately not possible to access such information. 
Best regards

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John E KVAM
John E KVAMBest answer
ST Employee
December 18, 2023

Anne is correct in that it's not possible. But it leaves you wondering why. Turns out the photon data is coming in at something like 20 million photons per second. And we need to aggregate all that information, make a decision and get that decision back to the MCU in pretty short order. So we lose the data you want at the hardware level.

The sensor can decide which SPADs are on - but that happens before the collect. The Dynamic SPAD Selection is based on how many photons were received last collect. 

And we know about the optical sensor due to some really careful factory calibration. It's not real-time data.

 

If this or any post solves your issue, please mark them as 'Accept as Solution' It really helps. And if you notice anything wrong do not hesitate to 'Report Inappropriate Content'. Someone will review it.
    SCH23Author
    Associate
    December 18, 2023

    Hi John

    Thanks a lot for your answer! I was just wondering whether it is possible to access this data because there is a utility function for selecting a ROI and I don't quite understand how this is supposed to work without knowing the intensity distribution.

    Anyway, I suppose that for the VL53L4CX this does not matter too much and I can just select the default 16x16 ROI. 

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